|10:00am - 12:00pm||Registration|
|10:00am - 12:00pm||Team Meetings|
|12:00pm - 2:00pm||Lunch|
|2:00pm - 5:30pm||Team Meetings|
|8:00am - 9:00am||Registration|
|9:00am - 12:00pm||Opening Session|
|12:00pm - 2:00pm||Lunch|
|2:00pm - 3:30pm||A2-ID32070: CLIMATE-TPE|
|ATMOSPHERE - CLIMATE - CARBON|
Monitoring Water and Energy Cycles at Climate Scale in the Third Pole Environment (CLIMATE-TPE)
1University of Twente, the Netherlands; 2Institute of Tibetan Plateau Research, CAS, China; 3Northwest Institute for Eco-Environment and Resources, CAS, China; 4Universitat de Valencia, Spain; 5University of Córdoba, Spain; 6University of Munich (LMU), Germany; 7National Meteorological Center, China Meteorological Administration, China; 8China Three Gorges University, China
The objective of this CLIMATE-TPE project is: To improve the understanding of the interactions between the Asian monsoon, the plateau surface (including its permafrost and lakes) and the Tibetan plateau atmosphere in terms of water and energy budgets in order to assess and understand the causes of changes in cryosphere and hydrosphere in relation to changes of plateau atmosphere in the Asian monsoon system and to predict the possible changes in water resources in the Third Pole Environment. A core innovation of the project is to verify or falsify recent hypotheses (e.g. links between plateau heating and monsoon circulation, snow cover and monsoon strength, soil moisture and timing of monsoon) and projections of the changes of glaciers and permafrost in relation to surface and tropospheric heatings on the Tibetan plateau as precursors of monsoon pattern changes and glaciers retreat, and their impacts on water resources in South East Asia.
We use earth observation, in-situ measurements and modelling to advance process understanding relevant to monsoon scale predictions, and improve and develop coupled regional scale hydroclimatic models to explain different physical links and scenarios that cannot be observed directly. Three work-packages (WP) are defined in the project to address three specific objectives. Objective 1) advancement of the understanding of microwave scattering and emission under complex terrains with permafrost and freeze – thawing conditions. The focus is to reduce current uncertainties in microwave satellite observations over complex terrain and improve retrieval accuracies of soil moisture and freeze-thaw states by deploying in-situ observations, laboratory experiment and numerical modelling. Objective 2) Advancement of physical understanding and quantification of changes of water and energy budgets in the TPE. The focus here is to integrate current understandings in the mechanism of changes in water and energy budget in TPE using satellite data products and numerical modelling. Objective 3) Advancement of quantifying changes in surface characteristics and monsoon interactions. All variables related to water and energy budgets in TPE will be subject to systematic analysis to endure their consistence in terms of climate data records. The variables will include albedo, vegetation coverage, soil thermal and hydraulic properties, LST, soil moisture, lake levels and land use changes among others.
In this contribution we focus on WP1: Observation and modelling of microwave scattering and emission under complex terrains and including permafrost and freeze and thawing.
We have deployed the ESA L-band (1.41 GHz) Radiometer (ELBARA-III, Schwank et al. 2010) since the beginning of 2016 at the central micrometeorological station (latitude: 33.919750, longitude: 102.153183, WGS’84) of the Maqu network of the Tibetan Plateau. ELBARA-III is provided by ESA for experimental observation for the calibration and validation of SMOS data and products.
1) We have conducted ELBARA measurements, covering one complete freeze-thawing cycles, for advancing understanding of the mass and energy exchanges involved in the freeze/thaw process.
2) The collected ELBARA observations are analysed with the recently developed effective temperature model by Lv et al. (2014) to better understand the microwave emission signals, including the validation of ESA’s SMOS and NASA’s SMAP radiometer brightness temperatures (TB).
3) The collected ELBARA and other in-situ data are used to investigate the effectiveness in two recently developed methods to merge existing satellite data of different frequencies (e.g. for low resolution data SCAT/ASCAT, SSM/I, AMSRE-E/2, SMOS, and high resolution data ASAR/S-1) (Dente et al. 2014; Lv et al. 2014), so that a consistent soil moisture data product can be generated by using the same consistent framework, contributing to the ESA Climate Change Initiative.
Young scientists engaged in this project:
Monitoring Water and Energy Cycles at Climate Scale in the Third Pole Environment (CLIMATE-TPE) (ID. 32070)
1Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101; 2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China; 3University of Chinese Academy of Sciences, Beijing 100049, China; 4Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede 7500 AA, Netherlands; 5School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China; 6Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; 7National Meteorological Center, Beijing 100081
The Third Pole Environment (TPE) centered on the Tibetan plateau and the Himalayas feeds Asia s largest rivers which provide water to 1.5 billion people across ten countries. Due to its high elevation, TPE plays a significant role in global atmospheric circulation and is highly sensitive to climate change. Intensive exchanges of water and energy fluxes take place between the Asian monsoon, the plateau land surface (lakes, glaciers, snow and permafrost) and the plateau atmosphere at various temporal and spatial scales, but a fundamental understanding of the details of the coupling is lacking especially at the climate scale.
Surface Soil Moisture Retrieval From Optical/Thermal Infrared Remote Sensing
1Department of Geography, Ludwig-Maximilians-Universität München, Munich, Germany; 2University of Chinese Academy of Sciences, Beijing, China
Surface soil moisture (SSM) plays a significant role in various domains of science such as agriculture, hydrology, meteorology and ecology. However, the spatial resolution of microwave SSM products is too coarse for regional and local applications. Most of the current optical/thermal infrared SSM retrieval models cannot estimate the quantitative volumetric soil water content directly without establishing empirical relationships between SSM measurements and satellite derived proxies of SSM. Therefore, this study mainly estimates SSM directly from Chinese geostationary meteorological satellite FY-2E data with a high spatial resolution of 5 km based on an improved elliptical SSM retrieval model developed from the synergistic use of the diurnal cycles of Land Surface Temperature (LST) and Net Surface Shortwave Radiation (NSSR). The original model is developed with bare soil. The coefficients of the original model are not distinguished from different Fractional Vegetation Cover (FVC). To optimize the model for SSM estimation at regional scale, the present study improved the original model by accounting for the influence of FVC, which is based on a dimidiate pixel model and MODIS NDVI product. Ultimately, a preliminary validation was conducted using the ground measurements in the south of Maqu City, in the source area of the Yellow River. A correlation coefficient (R) of 0.620, a root mean square error (RMSE) of 0.146 m3/m3 and a bias of 0.038 m3/m3 are found between in-situ measurement and FY-2E-derived SSM from original model. While it reveals a better relationship between FY-2E-derived SSM from improved model and ground measurement with a R of 0.845, a RMSE of 0.064 m3/m3 and a bias of 0.017 m3/m3. In order to provide more accurate SSM, high accuracy FVC, LST and NSSR are still needed. In addition to the point scale validation, cross comparison with other existing SSM products will be conducted in the future studies.
Monitoring sensible heat flux over urban areas in a high-altitude city using Large Aperture Scintillometer and Eddy Covariance
1Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, The Netherlands; 2Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
Urbanization leads to modifications of surface energy balance which governs the momentum, heat and mass transfer between urban canopy layer and the atmosphere, thus impacts dynamic processes in the urban ABL and ultimately influence the local, regional and even global climate. It is essential to obtain accurate urban ABL observations to enhance our understanding of land-atmosphere interaction process over the urban area and help to improve the prediction ability of numerical model. However, up to now, there are rarely observations in high-altitude cities. This poster introduced the urban flux observation conducted in a high-altitude city, Lhasa, using eddy-covariance technique and large aperture Scintillometer. As the first results, the diurnal patterns of the surface energy balance and energy partitioning in the winter of 2016 were discussed.
Evaporation and energy budget observation over a high-altitude small lake on the Tibetan Plateau
1Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101; 2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China; 3University of Chinese Academy of Sciences, Beijing 100049, China; 4Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede 7500 AA, Netherlands; 5School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
Lakes are an important part of the landscape on the Tibetan Plateau. The area that contains most of the plateau lakes has been expanding in recent years, but the impact of lakes on lake-atmosphere energy and water interactions is poorly understood and precise measurements of evaporation and understanding of the physical controls on turbulent heat flux over lakes at different time scales is rarely studied due to lack of observational data. To meet the above demands, an eddy covariance observational system was built above the water surface of the small Nam Co Lake (with an altitude of 4715 m and an area of approximately 1.4 km2, mean depth of 7 m) in April 2012 and the results are given by using data over ice free periods in 2012 and 2013 as follows: Firstly, the roughness length for momentum is 3.35×10-4 m over the small lake and the atmosphere is dominated by unstable and neutral conditions. The proper Charnock coefficient (α=0.031) and the roughness Reynolds number (R_r=0.56) for z_0m simulation are obtained for Bulk aerodynamic transfer model (B model) simulation. The simulated heat flux is validated independently with observations in 2013. The B model, with parameters optimized for the specific wave pattern in the small lake, could provide reliable and consistent results with EC measurements, and B model simulations are suitable for data interpolation due to inadequate footprint or malfunction of the EC instrument. Secondly, wind speed shows significance at half-hourly time scales, whereas water vapor and temperature gradients have higher correlations over daily and monthly time scales in lake-air turbulent heat exchange. Lastly, the total evaporation in this small lake (approximately 812 mm) is approximately 200 mm larger than that from adjacent Nam Co (approximately 627 mm) during their ice-free seasons. Moreover, the energy stored during April to June is mainly released during September to November, suggesting an energy balance closure value of 0.97 over the entire ice-free season. These results provide a foundation for application of remote sensing data over the high-altitude small lakes.
|2:00pm - 3:30pm||B2-ID32292: New EO Data & Operations|
|OCEANS & COASTAL ZONES|
Activities related to Dragon-4 project 32292 “The research of new ocean remote sensing data for operational application”, first year (2016-2017)
1isardSAT, Spain; 2First Institute of Oceanography, China
With contributions from: Markku Similä, Xi Zhang, Bernat Martinez, Jungang Yang, Jacqueline Boutin, Jin Wang, and their co-authors.
The project is divided into three major parts: (1) development of an algorithm for the retrieval of sea surface salinity based on combined active/passive microwave imagers; (2) data validation and oceanic application of new satellite altimeters and SWIM (“Surface Waves Investigation and Monitoring“, which is a scanning radar altimeter); and (3) devising techniques for sea ice parameter extraction and sea ice monitoring using data from most advanced satellite sensors.
The recent studies in part (1) deal with the development, evaluation and improvement of the sea surface salinity (SSS) retrieval algorithm under unfavorable conditions. A method for considering the effect of rain, implemented by the Chinese team, is based on L-band CAP (Combined Active-Passive) observations. The L-band GMFs (Geophysical Model Functions) are developed and the radiation characteristic of the rough sea surface is analyzed for rain-free and rainy conditions, respectively. Using this approach, the effect of rain-induced roughness can be corrected when calculating the SSS.
The objective of part (2) is the identification of eddies and their spatial-temporal variation characteristics on the Chinese seas using radar altimeters. The recent work of the European team is structured as a three-step approach: (a) improvement of retracker algorithms for the European altimeter missions, (b) development of geophysical corrections adapted to coastal zones, in particular focussing on the wet troposphere, (c) computations of geostrophic currents and derivation of mesoscale eddies. The Chinese partners recently have been working on inter-comparisons of data from Sentinel-3 SRAL, HY-2A RA, and Jason-2. The accuracy of, e. g., significant wave height retrievals as a function of the distance from the coast is analysed. The new algorithms shall be evaluated and validated in the next phases of the project (2018-2019) using in-situ and other reference data.
The work on sea ice monitoring (part 3) has been focussed on (a) the use of radar altimetry and SAR images for calculating ice thickness and sea ice concentration, and (b) a feasibility study concerning the performance of single-pass interferometric SAR for the retrieval of sea ice surface topography. The Chinese team, with contributions from the European partners, developed a new algorithm for retrieving the sea ice freeboard based on a new approximation of the echo waveform. This method resulted in more accurate freeboard estimates. A European group evaluated the achievable accuracy of ice surface height variations for different satellite InSAR configurations and analysed Tandem-X data acquired over sea ice as an example. Another Sino-European team concentrated on the determination of sea ice concentration and thickness from RS-2 ScanSAR images obtained over the Bohai Sea in winter 2012/2013.
In this introductory talk we will provide a brief overview of the different activities, which then will be described in more detail in subsequent presentations.
The Preliminary analysis and comparison of Sentinel-3 SRAL altimeter and HY-2A altimeter data in the China Sea
1The First Institute of Oceanography, S. O. A., China; 2isardSAT, Spain; 3Ocean Uiversity of China, China
ESA’s Sentinel-3 mission was successfully launched in February 2016. It carries a new altimeter-SAR Radar Altimeter (SRAL) which works on two modes of Low-Resolution Mode (LRM) and SAR mode. SRAL improves the along-track resolution (approximately 300m) in SAR mode using a delay/Doppler technique. SRAL is expected to provide even better measurements of sea surface height, significant wave height and wind speed than the conventional altimetry, especially in the coastal zone. In addition, Chinese first satellite altimeter-HY-2A Radar Altimeter (RA) has been in orbit more than 4 years, and Sentinel-3 SRAL and HY-2A RA are Simultaneous in orbit currently. In this study, sea surface height data of Sentinel-3 SRAL are analyzed by the comparison of the distribution and time series variability of SLA data between the different altimeters (Sentinel-3 SRAL, HY-2A RA, Jason-2) data and tide gauge data in the China Sea. Significant wave height data of SRAL are evaluated by the comparison with buoys data in the China Sea. The performance of SRAL observation over the coastal regions is analyzed. The accuracy and reliability of SRAL data are analyzed in the different locations with the different distances to the coast. Finally, the preliminary performance of Sentinel-3 SRAL and the evaluation of HY-2A RA in the China Sea are summarized.
Sea Surface Salinity Retrieval Under Rain Based On L-band Combined Active-passive Observations
1Qingdao University, China, People's Republic of; 2the First Institute of Oceanography, SOA, China
The sea surface salinity (SSS) is one of the key parameter for scientific community to understanding the ocean better. Equipped with an L-band radiometer, SMOS and Aquarius provide an unprecedented SSS data set of the global oceans. Enormous efforts are devoted to the development, evaluation and improvement of the SSS retrieval algorithm especially under some unfavorable conditions, i.e., the rain. Rain drops induce freshening and roughness effect to the sea surface. The fact that both mechanisms causing TB to increase makes it challenging to retrieval sea surface salinity when it rains. This presentation describes a method to retrieval the SSS under the rainy conditions based on the L-band CAP (Combined Active-Passive) observations. The L-band GMFs (Geophysical Model Functions) are developed and the radiation characteristic of the rough sea surface is analyzed for the rain free and rainy conditions respectively. The excess emissivity of H/V polarization is found to rise as the rain rate increases with a slope of 0.0003/mm·h-1, which means a 1-psu error at the rain rate of 10mm/h. The dependence of the sea surface emissivity (sensitive to both roughness and freshening) on the backscatter (only sensitive to roughness) is obtained and the rain-induced roughness effect is corrected. The bias of retrieved SSS shows no clear dependence on the rain rate and the standard deviation of SSS error is about 0.5psu. The above results confirm the feasibility of this new retrieval algorithm for the SSS remote sensing in the rainy weather with the CAP observations.
Estimating Sea Ice Concentration and Sea Ice Thickness in the Bohai Sea
1Finnish Meteorological Institute, Finland; 2National Satellite Ocean Application Service, China
Scientists from the Chinese National Satellite Ocean Application Service (NSOAS) and the Finnish Meteorological Institute (FMI) have jointly studied two fundamental sea ice parameters, sea ice concentration (SIC) and sea ice thickness (SIT) in the Bohai Sea. The case study was motivated by the risks the sea ice can cause for off-shore activities. Although the ice season is relatively short, usually from December to March, it can cause damage even in mild winters. On average level-ice thickness varies from 20 to 40 cm depending on the weather conditions.
We targeted the winter of 2012–2013 due to the availability of RADARSAT-2 (RS-2) ScanSAR imagery over the Bohai Sea. Our approach was to utilize several satellite sensors to create SIC and SIT charts.
The data set at our disposal consisted of 11 RS-2 SAR HH/HV images, daily AMSR2 imagery, four MODIS images and 31 in-situ measurements collected from the oil field platforms during the period from 2 January to 19 February 2013.
Basis for the calculations was the segmentation of SAR images using the Iterated Conditional Mode optimization and the extraction of different segment-wise features from them. The following texture features turned out to be the most useful in this connection: entropy, HH-polarization spatial autocorrelation, two quantities describing the shape of the variogram and HH-polarized corner points. These features were utilized in the SAR based SIC estimation. The scaled entropy alone yielded the best results in the SIT estimation.
The selection of the features in the SIC estimates was performed automatically by searching through all feature combinations and minimizing the residual error sum. Two different methods were tested: a linear model and a nonlinear Multi-Layer Perceptron neural network. Both approaches provided good results for very low or very high ice concentrations. For this data set, the linear model performed better. As a reference data we have used the in-situ measurements, the MODIS based SIC charts and the optical HJ-1B image.
The total ice volume in the study area was estimated using the thermodynamic sea ice model HIGHTSI with atmospheric boundary layer forcing (the reanalyzed ECMWF data). The ice drift was taken into account using the AMSR2 based ASI SIC chart with a resolution of 3.125 km. The ASI SIC chart was adjusted for the Bohai Sea conditions by the University of Bremen. The spatial distribution of the HIGHTSI SIT model field was then improved using statistics calculated from the AMSR2 data. The result was interpolated into a 1 km spatial grid and used as the background field h_B for the SAR based SIT estimation.
The background field and the SAR features were combined using a liner model that included a modulation term between h_B and each feature. Also here the minimization of the residual sum was the objective criterion in the feature selection. Somewhat surprisingly only a single feature, the scaled entropy, gave the best estimation results. As a reference data we used the MODIS based ice thickness chart as well as the field measurements.
The approach applied in this study has potential to be implemented operationally for the Bohai Sea ice service. However, more in-situ measurements as well as tuning the estimation model parameters are necessary, because the current study covers only one winter season. The obtained results should be regarded as guidelines for further research
A new CryoSat-2 sea ice freeboard retrieval algorithm using Bezier curve waveform fitting and offset center of gravity threshold method
1The First Institute of Oceanography, State Oceanic Administration, China; 2Nanjing University; 3Alfred Wegener Institute for Polar and Marine Research, German; 4Finnish Meteorological Institute, Finland
Altimeter waveform retracking correction is essential to get accurate sea ice freeboard. Some empirical fitting methods have been proposed, and these methods simulate the waveform by fitting to echo and empirically positioning the retracking point. In this paper, we develop a new method to retrack lead elevation by simulating the lead echo waveform using a composite cubic Bezier curve which is stable. The lead waveform is first divided into several segments, for each segment, the cubic Bezier curve is used to simulate the waveform. For ice, an improved offset center of gravity (OCOG) method is used. A new sea ice freeboard retrieval algorithm by using Cryosat-2 SAR-mode data is then performed combining the Bezier curve waveform fitting and an improved OCOG method.
The sea ice freeboard is calculated in following steps. The first step is to discriminate sea surface and the ice. The discrimination is based on the fact that the shape variation in echo waveform depending on whether the echo is dominated by specular reflections from leads, or by diffuses reflections from ice. The pulse peakiness (PP) and the stack standard deviation (SSD) parameters are used to discriminate the ice/water type. Returns from leads are identified by PP > 18 and a SSD<4, while echoes from ice floes are identified by PP < 9 and SSD > 4. Secondly, for echoes from leads, we use a more sophisticated Bezier curve to fit the echo to get retracking point, and the retracking point is set where rise reached 70% of the waveform maximum. For echoes from ice floes, a modified OCOG is used, and the retracking point is positioned at the point where the rise reaches 95% of the computed OCOG amplitude. Thirdly, to obtain an accurate freeboard, we obtain local sea level height as shown followed. We use a linear interpolation on the difference between lead elevations and mean sea surface height (MSS) for each Cryosat-2 track, and then yield the sea surface anomaly (SSA, the deviation between the actual sea surface elevation and the MSS). At last, the sea ice freeboard can be retrieved by sea ice surface elevations minus MSS and SSA.
We directly compare the freeboard retrievals by proposed method and L2I products of CryoSat-2 to IceBridge data. A mean bias of 1.3cm was found with the uncertainty of 0.025m which is a latitude-dependent gradient. For two IceBridge campaign periods in March 2015 and April 2016, mean differences of 1.57 and 1.09cm are for the freeboard retrievals by proposed method, while mean differences of 1.75 and 1.84cm are found when using Cryosat-2 L2I products. This suggests the proposed method is capable of reconciling the sea ice freeboard from radar altimetry data sets with a high accuracy.
Study On Global Ocean Wave Remote Sensing Data Products Based On The Multi-source Satellite
First Institute of Oceanography, State Oceanic Administration, China, People's Republic of
Ocean wave is a kind of fluctuation caused by the wind in the ocean. The ocean waves are very complex phenomena, the study of the ocean waves is of great significance on the marine engineering, marine development, transportation and shipping, marine fishing and aquaculture and other activities. In-situ observations, satellite remote sensing and numerical models are the important means of obtaining ocean waves information. Especially, satellite remote sensing is the important method of obtaining global ocean waves information synchronously. In this study, the significant wave height (SWH) of ocean waves obtained by T/P, Jason-1/2, ENVISAT, Cryosat-2 and HY-2A satellite altimeter and ENVISAT ASAR wave spectrum are used to generate the global ocean wave remote sensing data of 2000~2015 with the spatial and temporal resolution of 0.25° and one day. Firstly, all satellite data are validated and corrected by the comparison between them and the National Data Buoy Center (NDBC) buoys data. Then global ocean wave remote sensing data are obtained by the inverse distance weighting method. Finally, the resulting data are evaluated by the buoys data.
Research on Sea-ice Drift Using Doppler Shift Based on Sentinel-1 SAR Data
1College of Physics, Qingdao University, People's Republic of China; 2First Institute of Oceanography, State Oceanic Administration (SOA), China
In this paper, sea-ice radial drift is studied based on the single-look complex (SLC) data of Sentinel-1A/B SAR. The method for sea-ice drift retrieval is developed using Doppler shift. The estimated Doppler frequency and predicted geometric Doppler shift are calculated for each unit of the Doppler grid, then the Doppler centroid anomaly can be obtained. According to the analysis of the uncertainties from the orbit, attitude, antenna pattern, topography, etc., the error in the Doppler centroid anomaly can be eliminated as far as possible to acquire the standard Doppler centroid anomaly. Furthermore, the standard Doppler centroid anomaly is converted to sea-ice radial drift velocity. Finally, the developed method will be validated through the comparison with not only a conventional cross-correlation method, but also measurements from a drifting ice buoy.
Sea Surface Wind Speed Retrieval under Rain with the HY-2A Microwave Radiometer
Qingdao University, China, People's Republic of
HY-2A is the first satellite mission for the dynamic environmental parameters measurements of China which has been launched successfully on August 16th, 2011. The multi-bands scanning microwave radiometer (RM) is one of the key sensors onboard the HY-2A satellite with the primary objective of measuring SST, surface wind speed, water vapor and cloud liquid content from space. On the basis of HY-2A RM observations, the sensitivity of some brightness temperature (TB) channels to the rain rate and the wind speed are analyzed. Two TB combinations which show minor sensitivity to rain are obtained. Meanwhile, the sensitivity of the TB combination to the wind speed is even better to the original TB channel. Based on these TB combinations, a wind speed retrieval algorithm is developed and validated. The wind speed retrieval accuracy is better than 2 m/s for rainy conditions, which is evidently superior to the HY-2A RM standard product.
The Research on Strengthening Capability of SAR Sea Ice Drift Monitoring Based on Texture
1The First Institute of Oceanography State oceanic Administration, People's Republic of China,; 2Inner Mongolia University of Science and Technology, People's Republic of China
Sea ice is not only an important part of the global climate system, but also affects the development of oil ,gas and mineral resources in the Arctic. In addition, the sea ice can affect the perforation of the "Arctic Waterway" and cause harm to production activities such as sea-related production and maritime traffic. That monitor the sea ice drift and obtain accurate sea ice drift direction and speed is of great significance to the study of climate analysis, safe navigation of ships and management of offshore oil platform.
At present, all the study of sea ice drift monitoring is based on the intensity information of SAR satellite image. However, due to the influence of speckle noise, the Algorithms of ice motion monitoring could not work well. With the development of synthetic aperture radar (SAR) technology, the texture have been shown to greatly improve the classification ability of sea ice with SAR image. Therefore, the texture of sea ice SAR image is expected to improve the sea ice drift detection capability.
Based on the above, The Sentinel-1 SAR data were utilized to detect and analyze the strengthen ability of sea ice drift monitoring by using the SAR image texture. Eight kinds of texture features such as contrast, correlation, dissimilarity, entropy, mean were extracted from Sentinel-1 SAR data. A total of 66 sea ice samples which were divided into new ice, young ice and first year ice three types were selected for the experiment. First, normalized cross-correlation method is used to evaluate whether the texture is suitable for sea ice drift monitoring by comparing the following four results: match position is correct or not, the ratio of the maximum value and the second value of match results, the ratio of the maximum value and the mean value of match results, and the ratio of the maximum value and the triple variance of match results. In addition to that the effect of different sea ice types and resolution on the correctness of matching is analyzed from the results.
Then, the SURF method is used to evaluate the sea ice by comparing the following three results: the matching accuracy rate of from SAR image and eight texture, the correct matching logarithm of feature point, and the accuracy of correct matching feature pairs. The use of the SURF method for sea ice drift monitoring can produce many misaligned feature pairs, we use the following ways to determine the feature pairs is correct or not: The approximate velocity and direction of the sea ice drift are determined by artificial visual judgment, and then the velocity and direction calculated by the SURF feature point are considered correct which is within the error range of the approximate velocity and direction. The experimental results show that the texture feature is more suitable for the sea ice drift monitoring than the SAR image itself.
A Ship Detection Method Based on Coherence Optimal and Time-Frequency Decomposition
The First Institute of Oceanography, SOA, China, People's Republic of
Ship surveillance plays an important role in maritime traffic control, shipping safety, fishery supervision, maritime accident rescue, and oceanic rights protection. Synthetic Aperture Radar (SAR) has been widely used in ship surveillance as it has a full day, all-weather imaging capabilities. A great deal of research has been done on vessel detection using SAR; however, it is still difficult to detect the "weak" target under terrible sea conditions. The "weak" target with low target-sea contrast (TSC) is easy to be lost, and the existence of strong sea clutter can cause false alarm target. Therefore, this paper mainly focuses on the detection of "weak" vessels with polarimetric SAR.
1) High-resolution SAR sensors have a wide azimuth beam width, as well as a large range bandwidth. During SAR image formation, multiple squint angles and radar wavelengths are integrated to synthesize the full resolution SAR image. Based on this principle, the original single-look complex image SAR data was decomposed into different sub-aperture images in azimuth direction and sub-band images in range direction through time-frequency decomposition method. The scattering difference between the vessel and the ocean in the sub-aperture images or sub-band images is studied. We found that the vessel targets had coherence attributes between different sub-apertures, but the sea surface is significant differences and exists decoherence effect.
2) The complex coherence product of the sub-images polarimetric SAR is introduced and a plurality of sub images are formed into image pairs similar to the interferogram. Polarization coherent optimal parameter named PSCO (polarmetric SAR sub-aperture /spectral coherence optimal) is constructed by combining multiple sub images pairs and the concept of permanent scatterers’ detection in polarimetric interferometry. The performance of PSCO is tested using RADARSAT-2 quad-pol data. By comparing the enhancement ability of ship-sea contrast, the ability of clutter suppression and the calculation time, we choose 3 as the number of sub-images for PSCO. The CA-CFAR method is used to detect the ship for PSCO, and compared with CA-CFAR method based on HV polarization. The results show that the proposed method can suppress the sea clutter well and improve the detection performance. This method is suitable for terrible sea conditions, strong clutter and other complex sea background for vessel detection.
Study on the Distribution Characteristics of the Internal Waves on a Near-Global Scale Using ASAR and MODIS
the First Institute of Oceanography, China, People's Republic of
Internal waves occur almost everywhere on the shelves and slope. The generation and propagation of internal waves are closely related to the ocean bottom topography, tidal current, large-scale circulation and stratification. Therefore, internal waves have an obvious local property which shows different characteristics in different areas. Remote sensing data has been widely used in the temporal-spatial distributions, generation and evolution, parameter inversion of the internal waves and is the best instrumentality for detection of internal waves on a near-global scale. The MODIS imagery owns the advantages of large swath area and near-daily global coverage, but influenced by the weather greatly. SAR has the ability of all-weather and day-and-night observation, although data coverage is limited. This paper combines SAR and MODIS images effectively to observe internal waves on a near-global scale. The ASAR and MODIS imagery on global scale over the period of 2011 was processed. The distribution of internal waves is presented by extracting crests of internal waves. Regions of internal waves are frequently observed of Pacific, Indian Ocean and Atlantic of the internal waves are presented. The further analysis of the scale, propagation law and the temporal-spatial distributions characteristics of the internal waves in the typical occurrence area are also conducted.
Research on Extraction of ASAR Wave Mode SWH and MWP Based on SVM Regression Model
1Inner Mongolia University, Inner Mongolia Hohhot, China; 2the First Institute of Oceanography, China, People's Republic of
In this paper, a support vector machines (SVM) regression model is proposed to extract integral ocean wave parameters such as significant wave height (SWH) and mean wave period (MWP) from the ASAR wave mode images. Calibrated ASAR wave images can be applied directly to retrieve SWH and MWP without prior information. The model was established based on the nonlinear relationship between the sigma0, the variance of the normalized SAR image, SAR image spectrum spectral decomposition parameters, SWH and MWP. The input parameters of the SVM regression model are feature parameters extracted from ASAR images and the SWH provided by European Centre for medium range weather forecasts (ECMWF) is the output. A global data set of 30771 pairs of ASAR wave mode images and collocated ERA-Interim data from ECMWF is used to train SVM model. Based on the matching dataset, the particle swarm optimization (PSO) algorithm is applied to optimize the input kernel parameters of the SVM regression model and establish the SVM model. The SWH extracted by this model was compared with the ERA-Interim data and the buoy data. The RMSE of SWH is 0.34m and 0.48m and the correlation is 0.94 and 0.81, respectively. The MWP was also validated by ERA-Interim data and buoy data, the RMSE is 0.68s and 1.08s, and the Scatter Index is 0.04 and 0.09, respectively. The results show that the SVM regression model is an effective method to extract SWH from SAR data. The advantage of this model is that SAR data may serve as an independent data sources to extract SWH, which can avoid the complicated solution process of wave spectrum.
Construction Of Green Tide Monitoring System And Research On Its Key Techniques
1Shandong University of Science and Technology, China, People's Republic of; 2The Key Lab of Surveying&Mapping Technology on Island and Reef,SBSM, China, People's Republic of; 3The First Institute of Oceanography,SOA, China, People's Republic of; 4Tianjin Star GIS Information Engineering Co.,Ltd.,China, People's Republic of
Abstract：As a kind of marine natural disaster, Green Tide has been appearing every year along the Qingdao Coast, bringing great loss to this region, since the large-scale bloom in 2008. Therefore, it is of great value to obtain the real time dynamic information about green tide distribution. In this paper, methods of optical remote sensing and microwave remote sensing are employed in Green Tide Monitoring Research. A specific remote sensing data processing flow and a green tide information extraction algorithm are designed, according to the optical and microwave data of different characteristics. In the aspect of green tide spatial distribution information extraction, an automatic extraction algorithm of green tide distribution boundaries is designed based on the principle of morphology dilation/erosion. And key issues in information extraction, including the division of green tide regions, the obtaining of basic distributions, the limitation of distribution boundary, and the elimination of islands, have been solved. The automatic generation of green tide distribution boundaries from the results of remote sensing information extraction is realized. Finally, a green tide monitoring system is built based on IDL/GIS secondary development in the integrated environment of RS and GIS, achieving the integration of RS monitoring and information extraction.
Research on Key Technologies of Marine Oil Spill Monitoring System Based on Spaceborne SAR Images
1Shandong University of Science and Technology, China, People's Republic of; 2Key Laboratory of Surveying and Mapping Technology on Island and Reef, SBSM; 3North China Sea Marine Forecasting Center of SOA,Qingdao,China; 4Remote Sensing Department,the First Institute of Oceanography,SOA,Qingdao,China
A series of oil spill accidents has occurred frequently with the development of petroleum industry and marine oil transportation,which lead to serious oil pollution.For instance,the oil spill in Penglai,China 19-3 oil field and Dalian,Xingang,China has caused great ecological and economic losses,Therefore,it is meaningful for monitoring oil spill information in real time to prevent oil spill disasters.Based on the multi-source Synthetic Aperture Radar(SAR)image data,this paper has carried out research on the remote sensing monitoring of oil spill,and the operational monitoring system of marine oil spill based on Geographic Information System(GIS)is developed,which realize the integration of preprocessing multi-source remote sensing image data,extracting oil spill monitoring information,making oil spill thematic map and publishing oil spill monitoring reports.In order to realize the rapid processing of multi-source image data integration,the original data is analyzed based on Geospatial Data Abstraction Library(GDAL)open source raster spatial data conversion library and realized image reading,geometric correction and so on;the algorithm of multi-scale image segmentation and gray contrast characteristic extraction are encapsulated on the basis of the previous step,which achieve automatic processing of SAR image block,segmentation,oil spill identification,merging,parameter assignment,etc,the one-key processing of oil spill extraction is realized;for the application demand of oil spill monitoring,production of various kinds of standardized products, automatically add the elements of cartographic decoration elements,image parameters,oil spill area,the source of oil spill and other kinds of information,real-time generate thematic reports.
|2:00pm - 3:30pm||C2-ID32442: EOWAQYWET|
|HYDROLOGY & CRYOSPHERE|
The Potential of Earth Observation Time Series for the Assessment of Wetland and Water Shed Dynamics
1German Aerospace Center (DLR), Oberpfaffenhofen, Germany; 2Jiangxi Normal University, Nanchang, China; 3Max Planck Institute for Ornithology, Radolfzell, Germany; 4ICube, University of Strasbourg, France
The Poyang Lake and Dongting Lake are Chinas two largest freshwater lakes. Located in the middle reaches of the Yangtze River catchment these large floodplain lakes are home to four Ramsar sites initiated by the UNESCO, to foster wetland conservation. The wetlands in and around the lakes provide numerous important ecosystem services for human well-being, e.g. freshwater resources, retention area for Yangtze River floods, buffer for drought events, natural habitats for millions of endemic and migratory birds, etc. However, anthropogenic influences and related degradation of the lakes wetlands have dramatically increased.
In the project presentation current advances and first results of EO data analyses will be exhibited. EO data, especially from the new European Sentinel-family available since 2014, provide high-resolution information about the Earth surface. Multi-sensor satellite data are used to generate time series for the assessment of water surface and wetland dynamics. Qualitative and quantitative analyses will provide insights into the changes on the Earth’s surface in and around the Yangtze flood plain lakes that have taken place due to anthropogenic influence during the last 10 to 15 years. The results show that: Both lakes have shown a shrinking trend in water surface extent. Wetlands are increasingly used for natural resources exploitation, e.g. sand mining on lake ground and the cultivation of economically important plants at lake shores.
Within the project duration the potential of newly available Sentinel-data in combination with historic satellite data (Landsat, Envisat, etc.) and Chinese satellite data will be demonstrated for the generation of longer and preferably consistent Earth observation time series.
Analysis of the Relationship between Water level and Natural Water Surface in Poyang Lake
Key Laboratory of Poyang Lake Wetland and Watershed Research, Ministry of Education, Jiangxi Normal University, Nanchang, China
The spatial and temporal variation characteristics of the inundation extent for a lake have a great influnce on landscape structure and function of wetland ecosystem. Poyang Lake is the largest freshwater lake in
China. Poyang Lake wetland is a very important wetland in the world for biodiversity conservation. It is very important to measure accurately the water surface dynamics of the Poyang Lake. In this paper, the scatterplot between lake level and MODIS-derived inundation area of the Poyang Lake was used as a starting point, and the uncertainty of inundation areas with lake water levels was discussed. The results showed that: (1) though a significant linear relationship was found for the water level and inundation area for the Poyang Lake, the water surface area shows uncertainty; (2) Water level in Poyang Lake is higher in the south and lower in the north when lake water level is low, and the spatial heterogeneity of water level was decreasing with lake level increasing; (3) Water level slope in Poyang Lake in the time period of water withdrawal was greater than that in flood period; (4) Affected by fishery practice by levees of dish-shaped sublakes, the water surface area of the sublakes in water withdrawal period is greater than that in flood period. Sand mining also changed the water extent around the sandpits when in low lake level. Therefore the inundation extent for Poyang Lake was affected by topography of lake basin, water discharge from the tributaries in Poyang Lake watershed, and the backwater effect of the Yangtze River, as well as with human activities such as sand mining and fishing practice with levees.
|2:00pm - 3:30pm||D2-ID32244: Geohazard and Risk Assessment|
|SOLID EARTH & DISASTER RISK REDUCTION|
Generic InSAR atmospheric water vapour correction model
Newcastle University, United Kingdom
Atmospheric water vapour effects represent one of the major error sources of repeat-pass Interferometric Synthetic Aperture Radar (InSAR), and limit the accuracy of InSAR derived surface displacements. The spatio-temporal variations of atmospheric water vapour make it a challenge to measure small-amplitude surface displacements with InSAR. In previous studies, several InSAR atmospheric correction models have been successfully demonstrated: (1) Ground based correction models such as those using Global Navigation Satellite System (GNSS) observations. Such correction models are limited by the availability (and distribution) of ground observations. (2) Space based correction models including those involving NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and/or ESA Medium Resolution Imaging Spectrometer (MERIS). They are sensitive to the presence of clouds and there might be a time difference between space based water vapour and radar observations. (3) Numerical Weather Model (NWM) based correction models including those using European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and/or Weather Research and Forecasting (WRF). Similar to space based correction models, there might be a time difference between NWM and radar observations. Taking into account the inherited advatanges and limitations of GNSS, MODIS and ECMWF water vapour products, we present a global and near-real-time InSAR atmospheric correction model in this paper.
Tropospheric delays can be routinely retrieved from ground based GNSS arrays in all-weather conditions and also in real-time. We develop an Iterative Tropospheric Decomposition (ITD) interpolation model that decouples the total tropospheric delays into (i) a stratified component highly correlated with topography therefore delineates the vertical troposphere profile, and (ii) a turbulent component resulting from disturbance processes (e.g., severe weather) in the troposphere which trigger uncertain patterns in space and time. The decoupled interpolation model can then be employed to generate improved dense tropospheric delay maps compared with previsous GNSS-based models. In order to deal with areas with limited (or no) GNSS stations, we introduce the operational high resolution ECMWF (HRES-ECMWF, ~16 km), available near real-time, as well as MODIS near IR water vapour data whenever available as constrains of the ITD model, which makes the correction model globally available in all-weather conditions at any time for the first time. The applications of the ITD model to Sentinel-1 interferograms show that approximately 68%-78% of noise reduction can be achieved.
The study of the artificial source signal observed by CSELF network for earthquake precursor monitoring
1China Earthquake Administration, China, People's Republic of; 2Ulster University, UK
Foundation: National Science Foundation of China (No.41374077)
The first Control Source Extremely Low Frequency (CSELF) network has been built recently under the support of National Development and Reform Commission of China, which distributed in the Beijing Capital Area (BCA) and Southern Section of South North Seismic Belt (SNSB) in China for earthquake monitoring study. The network can be a part of earthquake stereoscopic monitoring system when it is combined with the satellite observation.
The network can not only receive the natural electromagnetic signal but also the artificial electromagnetic signal from the powered transmitter. A experiment of the system has been performed during 2016. The powered artificial electromagnetic signals are transmitted from 5:00 to 7:00 and from 17:00 to 19:00(GMT+8) every day. The signals at 4 different frequencies (216, 63, 12.3, 3.46 Hz) are transmitted and recorded. The natural electromagnetic signal from 1000Hz to 1000s are recorded continuously. The five electromagnetic components (North-South electric field :Ex, East-West electric field: Ey, North-South magnetic field: Hx, East-West magnetic field: Hy, and vertical magnetic field：Hz) are measured at each station of the network. The spectra of each component, impedance tensor, apparent resistivity and Impedance phase etc. are calculated using the similar software to MT data processing software. The original time series and the preliminarily processed results are transferred to the data center in the Institute of Geology, China Earthquake Administration through the CEA intranet. The further data processing and analysis are carried out in the institute for earthquake monitor study.
The artificial source electromagnetic signal is analyzed in both time and frequency domain. The adaptive filtering method was used to the raw time series data to extract the target frequency’s signal. The preliminary result showed that the amplitudes of the electromagnetic field of the artificial signals are obviously bigger than those of the natural signal. The power spectral density of the artificial signals are about 1-2 decades bigger than the natural signals for the same frequencies. The polarization characteristics of the electric and the magnetic field are studied for both source signals and the relationship between them are studied.,
In addition to the study in the feature of the artificial source electromagnetic field, we are making a tentative research on the relationship between the electromagnetic variation and the earthquake events. Some anomalies before and after Jinggu M5.9 earthquake (Dec.6, 2014) appeared in the observed data at Jinggu station for recorded natural signals. The spectrum variations appeared before and after Litang M5.1 earthquake (Sep. 23,2016) in the observed data at Jinggu station for recorded artificial signals.
First Gaofen-3 SAR interferometry evaluation
1COMET, School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom; 2China Academy of Space Technology, Beijing Institute of Space System Engineering, Beijing, 100086, China; 3Institute of Crustal Dynamics, China Earthquake Administration, Beijing, 100085, China
Spaceborne InSAR has been a well-known established technique since the first Earth-observing SAR satellite ERS-1 was launched on 17 July 1991. Cross-track InSAR can produce a digital elevation model (DEM), and differential InSAR (DInSAR) is able to measure crustal movement and deformation caused by, for example, subsidence, landslide, earthquake, volcanic, and glacier flows. Today, Synthetic Aperture Radar (SAR) data are acquired globally from many modern satellites: Sentinel-1 operated by the European Space Agency, ALOS-2 operated by the National Space Development Agency of Japan, Radarsat-2 operated by the Canadian Space Agency, TerraSAR-X and TanDEM-X operated by the German Space Agency, and the COSMO-SkyMed constellation operated by the Italian Space Agency.
Gaofen 3 (GF-3), as a Chinese ocean surveillance satellite, was launched from the Taiyuan Satellite Launch Centre on 10 August 2016, and has been in operation since January, 2017. It carries a multi-polarized C-band SAR sensor and operates in 12 working modes, capable of imaging Earth’s surface from high-resolution (1 m) to extremely-wide-swath (650 km). The advanced technological criteria of GF-3 satellite ensure high-quality SAR images, providing an opportunity for Chinese SAR interferometry (InSAR) study.
This work aims to verify interferometric ability of the level 1 SLC data and discuss the optional InSAR processing strategy for GF-3 satellite. Sample SAR data in strip map mode were collected in Tianjin and Shanghai to the InSAR test operations, and post-processed precise orbits are used to improve the coregistration. First, the azimuth offsets between azimuth spectra sub-looking images are investigated to confirm the SLC focusing quality. Second, DEM assisted coregistration (Arikan, M., 2007) is compared with the traditional polynomial method. The DEM assisted coregistration relies on the precise orbit, and it shows better coherence for GF-3 InSAR processing even in smooth topographic areas. By comparing the GF-3 interferogram with S1A result in Shanghai, an area of about 1 x 1 km are confirmed to be subsidence. The test results verify that GF-3 SAR data are capable in InSAR application of measuring ground movements, while continuous data acquisition and near real time precise orbit are necessary for scientific and engineering application in the future.
Arikan, M., van Leijen, F., Guang, L. and Hanssen, R.F., 2007, November. Improved image alignment under the influence of elevation. In Proceedings of FRINGE.
3D tomographic SAR imaging in densely vegetated mountainous rural areas in China
University College London, United Kingdom
3D SAR Tomography (TomoSAR) [1-4] and 4D SAR Differential Tomography (Diff-TomoSAR) [8-14] exploit multi-baseline SAR data stacks to create an important new innovation of SAR Interferometry, to sense complex scenes with multiple scatterers mapped into the same SAR cell. In addition to the 3-D shape reconstruction and deformation solution in complex urban/infrastructure areas [2,4], and recent cryospheric ice investigations , emerging tomographic remote sensing applications include forest scenarios [3,6,7], e.g. tree height and biomass estimation, sub-canopy topographic mapping, and even search, rescue and surveillance. However, these scenes are characterized by temporal decorrelation of scatterers, orbital, tropospheric and ionospheric phase distortion and an open issue regarding possible height blurring and accuracy losses for TomoSAR applications particularly in densely vegetated mountainous rural areas. Thus, it is important to extend characterisations of temporal decorrelation, orbital, tropospheric and ionospheric phase distortion.
We report here on 3D imaging (especially in vertical layers) over densely vegetated mountainous rural areas using 3-D SAR imaging (SAR tomography) derived from data stacks of X-band COSMO-SkyMed Spotlight and L band ALOS-1 PALSAR data stacks over Dujiangyan Dam, Sichuan, China. The new TanDEM-X 12m DEM is being used to assist co - registration of all the data stacks first. Then, atmospheric correction is being assessed using weather model data such as ERA-I, MERRA, MERRA-2, WRF; Linear phase-topography correction and MODIS spectrometer correction will be compared and ionospheric correction methods are discussed to remove tropospheric and ionospheric delay. Then the new TomoSAR method with the TanDEM-X 12m DEM is described to obtain the number of scatterers inside each pixel, the scattering amplitude and phase of each scatterer and finally extract tomograms (imaging), their 3D positions and motion parameters (deformation). A progress report will be shown on these different aspects.
This work is partially supported by the CSC and UCL MAPS Dean prize through a PhD studentship at UCL-MSSL.
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The 2015 MW 6.4 Pishan earthquake: fault constraints provided by InSAR techniques
Institute of Crustal Dynamic, China, People's Republic of
A 6.4-magnitude earthquake occurred near Pishan County on 3rd July, 2015. The epicenter was recorded at 37.459°N, 78.154°E, according to the USGS. The moment tensor solution from the USGS indicates that the earthquake was the result of a reverse fault rupture on a south-dipping fault (United States Geological Survey, 2015). This region is affected by the south-north converging India-Eurasia collision. The continental collision of the India and Eurasia plates is associated with a relative convergence rate of 40-50 mm/yr (Liu J. et al., 2015, Liang and Gan, 2013). Northward underthrusting of India beneath Eurasia has led to the development of the west Kunlun orogens and generates numerous earthquakes which consequently make this area one of the most seismically hazardous regions on Earth (United States Geological Survey, 2015). Using Synthetic Aperture Radar interferometry (InSAR), we mapped the near-field surface displacement of this event to better characterize, the seismic source parameters. Analysis of the interferograms obtained during ascending and descending orbits of the Sentinel-1A satellite in IW mode and modeling using a two-step inversion strategy suggest that this event involved thrust motion on a south-dipping fault. The best-fit slip model in the inversion suggests that the majority of the coseismic slip was concentrated on a thrust fault with a strike of 112°, a dip of 25° and an average rake angle of 89°. The maximum slip was ~1.2 m at a depth of ~12.5 km. The accumulative seismic moment was up to 4.5x1018 N×m, which is equivalent to a magnitude of Mw 6.4. The InSAR results supplied near-field geodetic measurements and provided independent constraints on the source parameters of this rupture.
Study on Coseismic Deformation and Correlation of Images in Nepal
1College of Resource Environment and Tourism of Capital Normal University; 2The Institute of Crustal Dynamics of China Earthquake Administration
In April 25, 2015, a strong earthquake occurred about 80 kilometers northwest of Kathmandu, the capital of Nepal. The surface wave magnitude measured by China Earthquake Network Center is Ms8.1 (http://news.ceic.ac.cn/CC20150425141126.html), and the moment magnitude calculated by the Harvard University CMT based on the focal mechanism is Mw7.9 (http://www.globalcmt.org/CMTsearch.html). And the magnitude of the Nepal earthquake is similar to that of the Wenchuan earthquake on the eastern boundary of the Tibetan Plateau in May 12, 2008. After the main shock, two aftershocks greater than magnitude seven broke out. The earthquake affected many parts of Nepal, Tibet, India, Chinese Bangladesh, Bhutan, caused a total of more than 30000 casualties. The earthquake is a thrust type earthquake that occurred in the subduction zone of Himalaya since the 8 magnitude earthquake in 1934. Most areas of Nepal are located in the mountains region of southern Himalaya. Although located on a small fault basin, the capital Kathmandu is still on the hanging wall of the Himalaya fault zone. The special terrain and geomorphic conditions cause the loss of radar coherent signal energy, which is not conducive to InSAR deformation observation. In addition, because the earthquake occurred in the heavily forested areas, in order to reduce the effect of forest on electromagnetic waves, to achieve the monitoring of surface deformation caused by the earthquake, this paper uses ALOS2/PALSAR2 dual polarization data to study. The data is the synthetic aperture radar data acquired and processed by the PALSAR-2 sensor on the ALOS-2 satellite. The working band of the sensor is L band, and the polarization of the data used in this paper is HH/HV. In this paper, we use the synthetic aperture radar differential interferometry to obtain the partial coseismic deformation field of Nepal earthquake. The results show that when the revisit period is short, InSAR technology plays an important role in the region, provide the deformation information of high signal-to-noise ratio for the earthquake. The InSAR results revealed that the Kathmandu region was strongly uplifted during the earthquake, and the area is the maximum deformation area. Corresponding to it, large surface subsidence occurred on the north side of Kathmandu, and the deformation field is consistent with the characteristics of pure thrust type earthquakes. In addition, in order to make full use of the dual polarization characteristics of the data, on the basis of obtaining the seismic deformation, this paper studies the correlation of polarization images. It is found that the intensity of polarization image changes before and after the earthquake. And we make a simple evaluation of the building damage in Kathmandu area. The results show that the extreme value of seismic deformation occurs in the west of Kathmandu City, and the low value of the correlation of polarization image also appears in the area. Therefore, there exists spatial correlation between deformation and image correlation. The correlation distribution of different polarization images is not completely consistent, perhaps because of the different degree of damage to the building. It provides a new way to detect the seismic damage of buildings by using multi polarization images.
Slip rate partitioning along the Dalbute fault zone (Northwest Junggar Basin) constrained by Small Baseline PS-InSAR
1Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing, China; 2School of Energy Resources, China University of Geosciences, Beijing, China; 3State Key Laboratory of Lithospheric Evolution, Institute of Geophysics and Geology, Chinese Academy of Sciences, Beijing, China
Outward growth and associated slip partitioning of the Tibetan Plateau is always a heated spot in the geosciences field worldwide. Dalbute fault zone is a rare transpressive fault along the northern margin of the Tibet, which plays an import role in absorbing the plateau’s northward expansion. And most importantly, the middle segmentation of the Dalbute fault zone is quite close to the Karamay City (less than 30 km in distance), a very important petroleum city in the Xinjiang Province, China. Therefore, the fault zone’s seismic activity has drawn the most consideration. GPS monitoring displays that, there occurs a sudden reduce (~5-8 mm/yr) in the northward velocities of the Tibet when cutting across the NE-SE-striking Dalbute fault zone. Previous researches attribute the rate drop to the fault’s over-thrusting. Except for the crustal thickening, we notice that the strike-slip directed displacement also takes part in the Tibet’s outward growth, like absorbing the northeastward extrusion of the Junggar Basin in the northern Tian Shan range. But this speculation lacks of quantification. Besides, whether the Heshituolegai basin, Tuoli basin, Baerluker Mountain are the termination tectonics of the Dalbute fault zone still remained unclear. We plan to apply radar images provided by the Dragon project to dig into these scientific questions. We use the Small Baseline PS-InSAR technique to quantify the slip rate field, faulting segmentation, seismic activity and the possible termination structures for the Dalbute fault zone. The slip partitioning mechanism between the strike-slip and thrusting submotions will also be constrained through the help of different flying azimuth (ascending and descending) of radar satellite and the verification from the campaign and permanent GPS measurements. This study is also a meaningful exploration for slip portioning mechanism among terminus of a transpressive fault arround the Tibet. This research will also provide some useful results for the future works on protecting against and mitigating earthquake disasters in the urban areas.
Seismic Damage Recognition Based on Watershed Segmentation of SAR Image Iexture Features
1Institute of Engineering Mechanics, China Earthquake Administration,China, People's Republic of; 2Institute of Crustal Dynamics, China Earthquake Administration, China, People's Republic of
Synthetic aperture radar (SAR) can penetrate clouds and haze and obtain information on ground conditions at various times of day and under different weather conditions. Since the 1950s, SAR has been widely used in the fields of surface subsidence monitoring, topographic mapping, resource exploration, environmental remote sensing and military applications, etc. In recent years, with the rapid development of SAR technology, building change detection in SAR images has become a research hotspot, especially after an earthquake. SAR technology can overcome the effects of bad weather and obtain images rapidly after earthquakes.
Information on seismic damage to buildings in SAR images from different time phases, especially in post-earthquake SAR images, is easily disturbed by other factors that affect the accuracy of information discrimination. To identify and evaluate the distribution of seismic damage accurately and make full use of the abundant texture features in the SAR image, a method for texture feature change detection in SAR images based on the watershed segmentation algorithm is proposed in this paper. We calculate the omnidirectional texture values of 8 types of texture features based on gray level co-occurrence matrices (GLCMs) .Based on the optimization of texture feature parameters, the principal components of feature parameters are segmented using the watershed segmentation algorithm, and the feature object image is obtained. Conventional methods of change detection based on texture features usually take the pixel as the calculating unit. This method introduces the concept of object orientation and carries out the calculation of the difference map at the object level. Finally, the classification threshold values for different levels of seismic damage are selected, and the identification of building damage is achieved. Using ALOS data from before and after the 2010 Yushu earthquake as an example to verify the effectiveness of the method, the overall accuracy of the building extraction is 88.9%. Compared with pixel-based methods, methods based on gray features, and methods based on single texture features, it is shown that the proposed method is effective.
The method made a breakthrough in the following ways. (1)Taking the texture feature object as the unit used in the change detection algorithm, the concept of object orientation is introduced to change detection, which represents a break from the conventional change detection methods that use the pixel as the unit.(2) The watershed segmentation algorithm is applied to texture features based on statistics, which makes the segmentation more meaningful.
Rapid buildingcollapse extraction using generalized optimum polarimetric contrast enhancementwith only one post-earthquake PolSAR image
Peking University, China, People's Republic of
Earthquake is among the most catastrophic natural disasters which seriously threat people’s lives and property. Since most of deaths and injuries in earthquakes are primarily caused by building collapse, rapid and accurate detection of collapsed buildings in urban areas is vitally important to emergency rescue and damage assessment. However, it’s often difficult to achieve suitable pre-event SAR data due to the unexpectedness and suddenness of earthquakes.
The polarimetric SAR (PolSAR) is capable of measuring the amplitude and phase of backscattered signals in four combinations of polarization. Moreover, it is sensitive to the characteristics of target like shape, size, material, structure and orientation. These make it become a potential data source to researches on building collapse extraction by using only post-earthquake SAR image. Based on this, many researches have been conducted (Li et al., 2012; Zhao et al., 2013). One issue existing is the misidentification of collapsed buildings and intact buildings which are not parallel to the SAR flight path since the scattering mechanism of the oriented intact buildings change to volume scattering dominant and reflection asymmetric. To eliminate this deficiency, the optimum polarimetric contrast enhancement (OPCE) method (Yang et al., 2000) is introduced to identify the collapsed buildings (Zhang et al., 2015). Using this method, the contrast of the intact buildings and collapsed buildings is enhanced through rotating the transmitting and receiving polarimetric antenna states. However, polarimetric information is not considered when applying this method. Yang et al. (2004) extended the OPCE method and combined it with the entropy and two polarimetric similarities, i.e. generalized optimum polarimetric contrast enhancement (GOPCE).
In this paper, we propose a new building collapse identification method based on the GOPCE method and the corresponding process framework is also presented. Moreover, the homogeneity feature of the grey level co-occurrence matrix (GLCM) is introduced to modify the GOPCE method. The case study is Yushu county where a Ms 7.1 earthquake occurred on April 14th, 2010. One post-earthquake Radasat-2 PolSAR image acquired on April 21th is utilized to test the proposed methods. By comparing with the OPCE and GOPCE methods, the GOPCE combined with homogeneity method performs better and more collapsed buildings are correctly detected. The misclassification of collapsed buildings and oriented intact buildings is also reduced. Experiments show that our proposed method can meet both time efficiency and detection accuracy requirements of earthquake rescue.
This work is supported by the Dragon 4 Cooperation Program  and the National Natural Science Foundation of China .
Monitoring the activities of post-seismic geohazards in Sichuan (China) with Sentinel-1 observations
1Southwest Jiaotong University, China, People's Republic of; 2COMET, School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; 3Departamento de Ingeniería Civil, Escuela Politécnica Superior, Universidad de Alicante, P.O. Box 99, E-03080 Alicante, Spain
The 2008 Wenchuan earthquake resulted in thousands of geo-hazards including landslides, and debris flows. In this paper, we will attempt to use time series InSAR techniques to monitor the activities of two post-seismic geohazards, namely the Daguangbo landslide and the Wenjiagou debris flow.
Caused by the 2008 Wenchuan earthquake, the Daguangbao landslide is one of the largest landslides in the world. The whole mountaintop collapsed in the 2008 earthquake, leading to a height change up to 500 meters. TanDEM-X data is used to generate a high resolution post-seismic DEM in this paper. The high gradients of topographic errors and the decorrelation caused by vegetation in mountainous areas make the processing of Tandem-X data challenging. To solve this, we propose a re-flattening iterative method to generate a post-seismic DEM. 15 Sentinel SAR images were acquired during March 2015 to March 2016. The time series displacements of the Daguangbao landslide are obtained using our advanced InSAR TS+AEM method with the Sentinel-1 SAR images and high-resolution post-seismic TanDEM-X DEM. Four active zones are observed with a maximum displacement rate of 8 cm/year, suggesting that this landslide is still active even 8 years after the earthquake.
The Wenjiagou debris flow was the second largest landslide in the Wenchuan earthquake. The volume of the deposits is determined by comparing the post-seismic DEM derived from tandem-x data and the pre-seismic SRTM. In this site, a complex project has been set up to prevent potential debris flows by separating water and mud. Our InSAR results from Sentinel-1 observations (2015~2016) suggest that the source area of this debris flow is still active due to steep topography and rainfalls, whilst the project site and its downstream are stable. The impacts of this debris flow prevention project are to be discussed.
Mapping crustal deformation in the Red River Fault zone using InSAR
COMET, School of Civil Engineering and Geosciences, Newcastle University, NE1 7RU, United Kingdom
The Red River Fault (RRF) is a major strike-slip fault running about 1000 km from southeast Tibet to South China Sea. As a result of the collision of the India and Eurasian plates, the fault is complicated, the average displacement rate is 2 to 5 mm/year and decreases from north to south. Investigation of the fault deformation information is significant to study its dynamic pattern, however, the large topography variations make it difficult to collect ground observations using GNSS.
Interferometric Synthetic Aperture Radar (InSAR), as a valued geodetic tool, has been applied in mapping crustal deformation at the scale of hundreds of kilometres with a high spatial resolution (e.g. a few metres to tens of metres) over the past two decades. Sentinel-1A was launched in April 2014, Sentinel-1B in April 2016 and both have been collecting data routinely. In the RRF zone, Sentinel-1 data are being acquired every 12/24 days with both satellites. The small temporal baseline, together with small spatial baselines (i.e. orbital separations) greatly improve interferometric coherence at C-band. In addition, Sentinel-1 images cover a wide footprint, 250 km from near to far range in Interferometric Wide Swath (TOPS) mode. Since October 2014, there have been over 400 Sentinel-1 images collected from 4 descending and 3 ascending tracks covering the RRF zone. Also, over 1500 ALOS-1 images collected between 2007 and 2011 are available in this region, and ALOS-2 data are being systematically acquired since 2014. The long wavelength (L-band) of ALOS-1/2 ensures good coherence. All the above-mentioned factors make it now possible to use InSAR to monitor slow-slip crustal deformation in this region.
The SAR data are interferometrically processed using our automatic processing chain based on the InSAR Scientific Computing Environment (ISCE) software. The variable climate in RRF zone challenges InSAR observing and processing, we calibrate the interferograms for atmospheric water vapour using high-resolution ECMWF products. Finally, time series analysis is performed to determine the interseismic deformation rate of the RRF using the in-house InSAR time series inversion package (InSAR TS + AEM, Li et al. 2009). It includes an advanced network correction approach for residual orbital correction and an atmospheric phase screen estimation with a priori deformation model. The InSAR measurements will be discussed to implicate future seismic hazard in the RRF zone.
Li, Z., Fielding, E. J., Cross, P. 2009: Integration of InSAR Time-Series Analysis and Water-Vapor Correction for Mapping Postseismic Motion After the 2003 Bam (Iran) Earthquake. IEEE Transactions on Geoscience and Remote Sensing, Vol. 47, 9.
Evaluating the use of sub-Pixel Offset Tracking cf. dInSAR using TerraSAR-X Staring Spotlight data for monitoring landslides in the Three Gorges Region of China
Mullard Space Science Laboratory, University College London, United Kingdom
Conventional dInSAR techniques have been frequently used in the past for deformation mapping including the mapping of landslide activities. However, several difficulties arise when attempting to apply dInSAR in areas with steep slopes and rugged topography, high humidity and dense vegetation cover such as over the Three Gorges Region. In addition to these difficulties, it is shown that the maximum detectable displacement gradient of dInSAR can be exceeded in our case study area even when using the highest resolution TerraSAR-X data.
A sub-Pixel Offset Tracking approach (sPOT) is applied to monitor slow-moving landslides in densely vegetated and steep terrain. This approach is shown of being capable of measuring centimetre-level landslide rates by using natural scatterers in densely vegetated terrain in line with measurements derived from corner reflectors.
The potential and limitations of TSX-ST (TerraSAR-X Staring Spotlight) data on measuring surface deformation using dInSAR and offset tracking techniques are assessed through case studies on the southern banks of the Yangtze River, in particular whether the improvement of the resolution of Staring Spotlight mode helps to address some of the issues that were encountered previously.
In addition, we show how the TanDEM-X Coregistered Single look Slant range Complex (TDX CoSSC) data can be employed to produce a 6 m resolution DEM. The impact of using different sources of DEMs is then assessed on deformation measurements via offset tracking and dInSAR.
Finally, the relationship between landslide occurrence and possible hydrological driving factors is assessed to infer possible landslide mechanisms.
This work was partially supported by the China Scholarship Council (CSC) and UCL through a PhD studentship at UCL-MSSL.
A Comparison of InSAR Time Series Approaches for Monitoring Wide-Scale, Low-Magnitude Ground Surface Deformation
1School of Geographical and Earth Sciences, University of Glasgow, United Kingdom; 2COMET, School of Civil Engineering and Geosciences, Newcastle University, United Kingdom
For decades, crustal motion and surface deformation processes have been investigated with differential SAR Interferometry. This geodetic technique can lead to very good estimations of ground movement, when applied to co- and interseismic processes, land subsidence phenomena, landslides or volcanic motion with significant deformation magnitudes. However, its application still presents a challenge considering wide-scale, subtle ground movement that is hardly measurable with InSAR in the presence of often indistinguishable orbital, atmospheric or topographic noise.
Different SAR sensors such as ESA’s ERS-1/2, ESA’s Envisat ASAR, ESA’s Sentinel-1 and JAXA’s ALOS PALSAR are tested in this study to assess their capability to achieve the required accuracy in the interferometric phase for monitoring slow, low magnitude surface movements (in the low mm-level). This applies to, for example, observations of glacial isostatic uplift, interseismic strain accumulation or small subsidence processes.
The range of possible error sources, such as residual orbital artefacts or atmospheric water vapour, require to be addressed in order to allow the extraction of any subtle deformation signals. Their elimination from interferograms present the biggest challenge due to their ‘masking’ characteristic.
This study advances currently known time series inversion methods for deformation monitoring and mapping of natural hazards. Results from two InSAR time series approaches are compared. On the one hand, this comprises an improved time series inversion package developed at the University of Glasgow and Newcastle University (“InSAR TS+AEM”, Li et al. 2009), based on the more classical and well established Small Baseline approach. This includes an advanced network correction approach for residual orbital effects and an atmospheric phase screen estimation with an a priori deformation model. On the other hand, a new technique is tested for reducing image artefacts and to derive a time series from InSAR data: A combined approach of Principal Component Analysis and Independent Component Analysis aims to separate the desired ground deformation signal from unwanted noise in interferograms. The idea is to take advantage of the signals’ different spatial and temporal characteristics and to decompose the mixtures into statistically independent components in space and time to filter out geophysical deformation.
Li, Z., Fielding, E. J., Cross, P. 2009: Integration of InSAR Time-Series Analysis and Water-Vapor Correction for Mapping Postseismic Motion After the 2003 Bam (Iran) Earthquake. IEEE Transactions on Geoscience and Remote Sensing, Vol. 47, 9.
Remote sensing data application in information extraction of active faults in Damxung area of Tibet
1Institute of Crustal Dynamics, China Earthquake Adiministration, Beijing, China, China, People's Republic of; 2Institute of Disaster Prevention, Sanhe Hebei
Damxung area is the place where strong earthquakes happen frequently, and the former studies have shown that there is a close relationship between strong earthquakes and active faults in this place, so it is necessary for us to study the distribution, geometric structure and motion characteristics of the faults if we want to know the initiation mechanism and seismogenic environment of the earthquakes. In this paper, by using a wide range of remote sensing data such as Landsat-7 ETM+, ALOS, GF-2, Sentinel-1 and DEM data, and utilizing a wide variety of image enhancement technology such as multiband color composite, PCA and ratio analysis based on these data, active fault information was extracted and the remote sensing interpretation marks about active faults were established, and finally, we displayed the the distribution and activity of the Yadong-Gulu fault and the Jiali fault in the study area. Our results have shown that: the Yadong-Gulu fault mainly consisted of normal faults and strike slip faults, and it could be divided into three parts. The north part of the Yadong-Gulu fault had direction toward NNE with part of it buried, and normal faults developed associating with strike slip faults. The middle part of the Yadong-Gulu fault had direction toward NE, and the fault was exposed, and the main faults of it were sinistral strike-slip normal faults. The south part of the Yadong-Gulu fault had a direction toward NNE, which then changed to NS on south, and the fault was partly buried with many secondary faults around it, and it mainly consisted of dextral strike-slip normal faults which had formed many graben basins. The Jiali fault was buried partly in the study area and could be divided into two branches, and it was dextral strike-slip normal fault. The wide existence of fault triangular facet, pull-apart basin and river break in the remote sensing images revealed that this area had a tectonic background characterizing by stretch and twist, which was mainly governed by upwelling movement on vertical direction and extension movement on horizontal direction of the middle Tibetan Plateau which was caused by the subduction of the India Plate. The remote sensing interpretation in this paper reflected the current characteristics of faults’ activities in the study area, and the characteristics of these activities had a close relationship with the earthquakes. What’s more, the results of this study also showed that enhancement processing upon remote sensing image could highlight some specific landforms and geological structure information, and the remote sensing image had unparalleled advantages compared with field geological investigation, and remote sensing technology had a bright prospect in geological investigation and geological disaster monitoring.
Detection of surface deformation field of small earthquakes by InSAR technique
1Institute of Crustal Dynamics, China Earthquake Administration, China, People's Republic of; 2Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China
Abstract: The Qinghai Tibet Plateau is the world's youngest and most active plateau, due to the collision between the India plate and the Asian plate led to most of the region's fault zone is active, a lot of small earthquakes between Mw5.0 and Mw6.0 occurred every year, these small earthquakes can cause ground subsidence, influence in fault state. Based on the ENVISAT satellite data, the surface deformation caused by small Tibet earthquake were analyzed obtain the coseismic deformation field, comparative analysis the surrounding areas of land subsidence caused by the small earthquakes, and use the GPS data to verify, results showed that there was high consistency between the SAR data acquisition deformation and GPS measurement result.
Keywords: coseismic deformation, small earthquake, surface deformation
1. research status
The Qinghai Tibet Plateau is the world's youngest and most active plateau, with an average altitude of more than 5000 m, the main structural features currently are the results of the India plate and the Asian plate collision since the 50-60Ma. Because the impact time is new, tectonic collision and orogeny of the intact are save well, and many continental dynamic process after collision are continues, so the Tibetan Plateau is the most ideal place for the new structure research.
Qinghai Tibet Plateau is a strongly rising block surrounded by the surrounding active faults. The surrounding fracture surface tend to plateau interior, thus formed in the mountains around the edge of the plateau to plateau lowland obduction "coronary morphology structure". The type of peripheral plateau active tectonics dominated by fracture structure, its basic characteristics are the reverse fault internal fault dip plateau. The southern boundary of the Tibetan Plateau is the main boundary fault zone in Himalaya, the west adjacent to the Yika La Kunlun fault zone and the Pamir Plateau; the northern boundary along the northern margin of West Kunlun fault zone, the Altun fault and the northern margin of Qilian Mountains fault zone, curving to six mountain fault zone; the Eastern boundary along the Longmen Mountain Fault Zone, An’ninghe fault and Xiaojiang Fault with the extension of the twists and turns.
Select the Lhasa block as the study area, analysis the surface deformation of Mw5.0~6.0 earthquake in the study area, using the traditional two track difference method for data processing, the basic idea is to generate two pass interference using two images before and after of the surface change experimentation area, topographic information removed from the interferogram. Then can get the deformation information. The basic process is needed before the earthquake and after the earthquake SAR data and DEM data, the data before the earthquake as the main image formed interferogram with the post earthquake data, simulated interferogram using DEM, the simulated interferogram is subtracted from the interferogram by SAR data, then form the differential interferogram. The advantage of this method is that it does not need the phase unwrapping of the interferogram to avoid the difficulty of understanding, but also can obtain the precision of the deformation results.
2. research significance
The Qinghai Tibet Plateau is an earthquake prone area, especially some small earthquakes (Mw5.0~6.0). These earthquakes release the earth's crust stress, reduce the probability of strong earthquakes in the fault, and effectively alleviate the seismic risk in the region. At the same time, through the study of the mechanism of the occurrence of small earthquakes, we can obtain the geophysical parameters. It provides valuable information for the assessment of regional seismic hazard.
Study on deformation field of small earthquakes in Lhasa block since 90s of last century using InSAR technique. In March 24, 2010 the Tibet area (N32.51 degrees, E92.83 degrees) a Mw5.6 earthquake as an example, using the traditional differential method pass interference to obtain the coseismic deformation field of the earthquake, coseismic interferograms obtained using multiple sets of different seismic data, through data analysis to obtain the coseismic displacement of the interferometric phase, clear surface displacement caused by the earthquake. At the same time, the use of GPS data to verify the accuracy of the result, inverse the fault parameters based on coseismic deformation field and GPS data, to obtained the detailed parameters of fault, which can provide the basis for the subsequent study of fault and the mechanism of earthquake.
Detecting Seismic Anomalies from SWARM Satellites Using Big Data Analytics
1Ulster University, United Kingdom; 2Institute of Geology, China Earthquake Administration
This work will report the studies undertaken in the past year, which is aimed to developing viable methods and techniques for detecting anomalies from space and terrestrial electromagnetic data that are observed by the SWARM satellite and the network of the Control Source Extremely Low Frequency (CSELF) in China and investigating the correlation between anomalies and earthquakes. We have developed an effective algorithm for detecting anomalies from time series data and evaluated them over benchmark datasets, as well as preliminarily on electromagnetic data observed by the Swarm satellites and by the CSELF. We will present a number of issues related to the Swarm satellite data, the methods required to process the data, and finally present a comparative case study of the Jingpu earthquake using the Swarm and CSELF data.
|2:00pm - 3:30pm||E2-ID31470: FOREST Dragon 4|
|LAND & ENVIRONMENT|
Research progress of PolSAR technology in IECAS
Institute Of Electronics, Chinese Academy Of Sciences, China, People's Republic of
Within the framework of the DRAGON project, the Institute of Electronics, Chinese Academy of Sciences (IECAS) continuously had a tight collaboration with the European and the Chinese partners. Joint research is around the 3 scientific topics: hybrid-polarity (HP) architecture, vegetation classification, and multi-aspect polarimeric scattering mechanism.
Terrain Correction Methods For Multi-dimensional SAR Data Applied To Forest Above Ground Biomass Estimation
1The research Institute of Forest Resources Information Technique, Chinese Academy of Forestry,Beijing, China; 2Institute of Electronics, Chinese Academy of Sciences, Beijing, China; 3I.E.T.R -Univ Rennes 1, France
In this report, we will introduce the main research progress of forest above ground biomass (AGB) estimation study based on integration of multi-dimensional SAR data. It mainly contains the following three aspects. (1) We proposed a three-steps semi-empirical radiometric terrain correction approach for PolSAR data. The three steps of terrain effects correction are polarization orientation angle, effective scattering area, and angular variation effect corrections. Based on the LiDAR-derived forest AGB data, detailed analysis and evaluation were carried on for the three correction steps. (2) Base on the simplified InSAR decorrelation model (SINC model) and Algebraic Difference theory, we developed a terrain correction approach for coherence image of InSAR data. And the method was evaluated by space-borne and air-borne InSAR data. (3) Based on the X-band single-pass InSAR data and P-band PolSAR data acquired by multi-dimensional SAR system (CASMSAR) of China, we developed one combined estimation approach of forest AGB based on multi-dimensional SAR data by integrating the terrain correction methods proposed above.
Virtual Dispalacement Method for Tree Volume
Friedrich-Schiller-Universität Jena, Germany
Virtual Dispalacement Method for Tree Volume
|3:30pm - 4:00pm||Coffee Break|
|4:00pm - 5:30pm||Young Scientists Poster Session|
Location: Congress Hall
|5:30pm - 6:30pm||Welcome Cocktail|
|8:30am - 10:00am||A3-ID32271: Air Quality Over China|
|ATMOSPHERE - CLIMATE - CARBON|
Trends in NOx emissions and SO2 concentrations in China
1KNMI, Netherlands, The; 2AUTH, Greece; 3BIRA-IASB
To monitor air quality trends in China for the period 2005-2015 we derived SO2 columns and NOx emissions on a provincial level. To put these trends into perspective they are compared with public data on energy consumption and the environmental policies of China. We distinguish the effect of air quality regulations from economic growth by comparing them relatively to fossil fuel consumption. Pollutant levels, per unit of fossil fuel, are used to assess the effectiveness of air quality regulations. We note that the desulphurisation regulations enforced in 2005-2006 only had a significant effect in the years 2008-2009 when a much stricter control of the actual use of the installations began. For national NOx emissions a distinct decreasing trend is only visible since 2012, but the emission peak year differs from province to province. The last three years show both a reduction in SO2 and NOx emissions per fossil fuel unit, since the authorities have implemented several new environmental regulations. Despite an increasing fossil fuel consumption and a growing transport sector, the effects of air quality policy in China are clearly visible.
Evaluation of RSD-DRFs technique using deterioration experimental data
1Climate Research Group, Division of Environmental Physics and Meteorology, Faculty of Physics, National & Kapodistrian University of Athens, Greece; 2Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China
As a part of our research during the implementation of the DRAGON 3 project we have developed a new technique of using satellite observations to estimate the level of deterioration of the materials used in constructions and cultural monuments. This technique is mainly based on the already developed Dose Response Functions (DRFs) in which the ground-based measurements of various atmospheric pollutants (e.g. nitrogen oxides, sulphur dioxide, ozone) and several climatic parameters, such as air temperature and others, are often used as input data. The values of DRFs of specific materials provide a measure of their corrosion or soiling caused by their outdoor exposure to weather and the air pollution factors. In this work, we evaluate the performance of our proposed technique using the available deterioration experimental data from more than 10 European sites. These data were obtained during different periods since 2005 for cases of four materials (carbon steel, limestone, zinc, modern glass). The term “Remotely Sensed Data-Dose Response Functions (RSD-DRFs)” is proposed for this technique.
Ensemble of ESA/AATSR Aerosol Optical Depth (AOD) Products Based on the Likelihood Estimate Method with Uncertainties
RADI, China, People's Republic of
Within the ESA Climate Change Initiative (CCI) project Aerosol_cci, there are three Aerosol Optical Depth (AOD) datasets of Advanced Along Track Scanning Radiometer (AATSR) data. These are obtained using the ATSR-2/ATSR dual-view aerosol retrieval algorithm (ADV) by the Finnish Meteorological Institute (FMI)/University of Helsinki (UHEL), the Oxford-RAL Retrieval of Aerosol and Cloud algorithm (ORAC) by the University of Oxford/ Rutherford Appleton Laboratory (RAL) and the Swansea algorithm (SU) by the University of Swansea. The three AOD datasets vary widely. Each has unique characteristics, so none is significantly better than the others, and each has shortcomings that limits the scope of its application. To address this, we propose a method for converging these three products to create a single dataset with higher spatial coverage and better accuracy. The fusion algorithm consists of three parts: the first part is to remove the system errors; the second part is to calculate the uncertainty and fusion of datasets using the maximum likelihood estimate (MLE) method; and the third part is to mask outliers with a threshold of 0.12. The ensemble AOD results show that the spatial coverage of fused dataset after mask is 148%, 13% and 181% higher than ADV, ORAC and SU respectively, and the root mean square (RMSE), mean absolute error (MAE), mean bias error (MBE) and relative mean bias (RMB) are superior to the three original datasets. Thus, the accuracy and spatial coverage of the fused AOD dataset after mask are improved compared to the original data. Finally, we discuss the selection of mask thresholds.
Spatial and temporal variations of aerosols over China from multi-satellite observations.
1Finnish Meteorological Institute (FMI), Helsinki, Finland; 2National Observatory of Athens (NOA), Athens, Greece; 3Laboratory of Atmospheric Physics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece; 4Laboratory of Atmospheric Physics, Department of Physics, University of Patras, Patra, Greece; 5Department of Environmental Engineering, School of Engineering, Democritus University of Thrace, Xanthi, Greece; 6University of Derby, UK; 7Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences (RADI/CAS), Beijing, China; 8Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
Satellite data from several different instruments are used to study the spatial and temporal distribution of aerosols over China since 1995. In particular ATSR-2 (1995-2003), AATSR (2002-2012), MODIS (2000-present) are used to provide the spatial distribution of the AOD, while CALIOP (2007-present) also provides information on the vertical structure of aerosols, including aerosol type information and in particular dust. The AOD data sets are validated and evaluated versus sun photometer data from AERONET and the Chinese network CARSNET. This is particularly valuable because aerosol retrieval algorithms are developed and validated over areas where many independent ground-based observations are available, such as over the eastern USA and Europe. However, over these areas the AOD levels are often relatively low as compared to China where the occurrence of very high AOD, combined with the variation in aerosol type and surface characteristics, poses particular problems as regards data selection and discrimination between high AOD and the occurrence of clouds.
The spatial distributions over China varies significantly as a result of the multitude of sources, both natural and anthropogenic, which in turn vary with the season. These include anthropogenic sources such as industry and traffic, agricultural and natural biomass, dust from two major deserts, as well as the seasonal production of precursor gases. In addition, economic development and measures to improve air quality affect the long term variation of aerosol concentrations. Meteorology and large scale circulation including the seasonally progressing monsoon have a substantial effect on the aerosol physical properties as well as on production and removal of the aerosol particles. All of these effects vary with location over China and their seasonal and year-to-year variatons.
An initial analysis of the spatial and vertical variability of the AOD will be presented together with time series showing the variation over representative areas. Satellite derived information on aerosol precursor gases NO2, SO2 and BVOCs will be used in the analysis.
These activities are undertaken as part of the EU-FP7 project MarcoPolo. The main objective of the MarcoPolo project is to improve air quality monitoring, modelling and forecasting over China using satellite-retrieved information on aerosols, NOx, SO2, and biogenic gases. This information will be used in air quality models to invert emission estimates. The results, together with known information from ground-based measurements, will then be used to construct an emission database over China. The MarcoPolo project finished in March 2017 and will in part be continued in the framework of the ESA DRAGON4 initiative.
Bvoc Emissions and O3 in a Subtropical Plantation in China: Measurement and Validation
1LAGEO, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China; 2Department of Earth System Science, University of California, Irvine CA 92697, USA; 32B Technologies, Inc. Boulder, CO 80301, USA; 4Tufts University, Department of Civil and Environmental Engineering, Medford, MA 02155, USA; 5National Center for Atmospheric Research, Boulder, CO 80307, USA; 6National Center for Atmospheric Research, Boulder, CO 80307, USA; 7Royal Belgian Institute for Space Aeronomy, Avenue Circulaire 3, 1180, Brussels, Belgium
Atmospheric pollution is a severe problem in China, it is an important to keep on our monitoring and satellite validation of trace gases, BVOC emissions, aerosols in China, especially at some representative sites. Our main activities are ground observations, validation of satellite retrievals and satellite data applications. To fulfill one of all above tasks, measurements of BVOC emissions, O3 and solar radiation were carried out in a subtropical Pinus plantation in China during 2013-2016. BVOC emissions were measured using a relaxed eddy accumulation (REA) technique and a gradient technique. Monoterpenes were the dominant VOCs in this subtropical Pinus plantation. Isoprene and monoterpene emissions showed obvious diurnal, seasonal and inter-annual variations. In comparison with 2013, annual BVOC emissions decreased in 2015, which were associated with decreases of PAR, temperature and water vapor. O3 concentration above the canopy level also displayed clear diurnal variation. It was found that BVOC emissions were influenced by biomass burning smoke and pine florescence. The mean emission factors determined using the MEGAN model emission algorithms and empirical model of BVOC emissions were 0.71 and 1.19 mg m-2 h-1 for isoprene and 1.39 and 1.65 mg m-2 h-1 for monoterpenes, respectively. Flux measurements of BVOCs at a subtropical bamboo plantation in China were used to evaluate the bottom-up inventory of isoprene emissions and the satellite-based MarcoPolo (Monitoring and Assessment of Regional air quality in China using space Observations) emission inventory for isoprene derived using inversion of satellite columns of formaldehyde. Generally, the space-based inventory provides a satisfactory agreement with the observations in summer. Further validation in this subtropical plantation will be carried out in the future. All measure and validated data will be provided for air quality models, so as to improve our abilities in the forecast of air quality.
Key words: Biogenic volatile organic compounds; emission fluxes; ground measurement; validation; satellite.
Intercomparison of NOx Emission Inventories over East Asia
1Royal Netherlands Meteorological Institute (KNMI); 2Delft University of Technology; 3Japan Agency for Marine-Earth Science and Technology; 4Jet Propulsion Laboratory-California Institute of Technology; 5Nanjing University of Information Sciences and Technology; 6Asia Center for Air Pollution Research; 7Department of Environmental Engineering, Inha University, Inchon; 8Department of Earth System Science, Tsinghua University; 9Institute for Environment and Sustainability, Joint Research Centre
We compare 9 emission inventories of nitrogen oxides including four satellite-derived NOx inventories and the following bottom-up inventories for East Asia: REAS (Regional Emission inventory in ASia), MEIC (Multi-resolution Emission Inventory for China), CAPSS (Clean Air Policy Support System) and EDGAR (Emissions Database for Global Atmospheric Research). Two of the satellite-derived inventories are estimated by using the DECSO (Daily Emission derived Constrained by Satellite Observations) algorithm, which is based on an extended Kalman filter applied to observations from OMI or from GOME-2. The other two are derived with the EnKF algorithm, which is based on an ensemble Kalman Filter applied to observations of multiple species using either the chemical transport model CHASER and MIROC-chem. The temporal behaviour and spatial distribution of the inventories are compared on a national and regional scale. A distinction is also made between urban and rural areas. The intercomparison of all inventories shows good agreement in total NOx emissions over Mainland China, especially for trends, with an average bias of about 20% for yearly emissions. All the inventories show the typical emission reduction of 10% during the Chinese New Year and a peak in December. Satellite-derived approaches using OMI show a summer peak due to strong emissions from soil and biomass burning in this season. Biases in NOx emissions and uncertainties in temporal variability increase quickly when the spatial scale decreases. The analyses of the differences show: the importance of using observations from multiple instruments and a high spatial resolution model for the satellite-derived inventories, while for bottom-up inventories, accurate emission factors and activity information are required. The advantage of the satellite derived approach is that the emissions are soon available after observation, while the strong point the bottom-up inventories is that they include detailed information of emissions for each source category.
|8:30am - 10:00am||B3-ID32249: Parameters from Multi-sensors|
|OCEANS & COASTAL ZONES|
Some Results from Chinese Newly Launched Spaceborne Microwave Sensors
1Second Institute of Oceanography, SOA, China; 2National Ocean Technology Center, SOA, China; 3Nanjing University of Information Science & Technology, China; 4Ifremer, France
GF-3 (GF stands for GaoFen, which means High Resolution in Chinese) is the China's first C band multi-polarization high resolution microwave remote sensing satellite. It was successfully launched on Aug. 10, 2016 in Taiyuan satellite launch center. The synthetic aperture radar (SAR) on board GF-3 works at incidence angles ranging from 20 to 50 degree with several polarization modes including single-polarization, dual-polarization and quad-polarization. GF-3 SAR is also the world’s most imaging modes SAR satellite, with 12 imaging modes consisting of some traditional ones like stripmap and scanSAR modes and some new ones like spotlight, wave and global modes. GF-3 SAR is thus a multi-functional satellite for both land and ocean observation by switching the different imaging modes.
TG-2 (TG stands for TianGong, which means Heavenly Palace in Chinese) is a Chinese space laboratory which was launched on 15 Sep. 2016 from Jiuquan Satellite Launch Centre aboard a Long March 2F rocket. The onboard Interferometric Imaging Radar Altimeter (InIRA) is a new generation radar altimeter developed by China and also the first on orbit wide swath imaging radar altimeter, which integrates interferometry, synthetic aperture, and height tracking techniques at small incidence angles and a swath of 30 km. The InIRA was switch on to acquire data during this mission on 22 September.
This paper gives some preliminary results for the quantitative remote sensing of ocean winds and waves from the GF-3 SAR and the TG-2 InIRA. Comparisons to the ECMWF ERA-Interim reanalysis data show good agreements but more valuable details.
SAR Image Cross-spectral Analysis of Short Radial Waves: Directional Properties and its Applications to Wind-Wave-Current Retrieval
Laboratoire d'Ocanographie Physique et Spatiale (LOPS), IUEM, University of Brest, CNRS, IRD, Ifremer, Brest, France
Sentinel-1 wave mode operates in novel ‘leap frog’ acquisitionmode. A vignette is acquired every 100 km at two alternate incidence angles (23° and 36.5° respectively ), withtwo images at the same incidence 200km apart. This mode enables us not only to conduct global analysis for each incidence angle, but also to investigatethe dependence of geophysical parameters on incidence angles.
The SAR image cross-spectrum between a pair of sublooks separated in time has been widely used to help remove 180° ambiguity of detected ocean swell systems. Ocean swells move along the waves' propagation direction during this offset time of the order of SAR integration time (~0.4s for Sentinel-1), therefore, co- and cross-spectra can help to consistently estimate velocity characteristics of the randomly moving sea surface scatterers related to scales larger than SAR spatial resolution. The short radial waves longer than SAR spatial resolution but shorter than ocean swells are, to first order, driven by surface winds. Thus, a new parameter, averaged complex cross-spectra over short radial waves domain, is proposed to manifest impacts of wind speed and direction on these moving scatterers.
Large data sets have been constituted systematically by co-locating Sentinel-1A/Bwave mode acquisitions and ECMWF forecast winds. Efficiently, distinctive features are revealedfor two incidence angles as well as dual-polarizations.
Specifically, to first order,there exhibits a linear relationship between imaginary cross-spectra and radial winds. More encouragingly, it reaches the maximum at downwind (wind blowing toward to the antenna), drops to zero at crosswind (wind blowing along azimuth direction) and continuously decreases to the minimum at upwind. Its sensitivity to wind direction is potential to wind retrieval applications.
At 23° incidence, the spectral parameter does not exhibit up-to-downwind difference of spectral. At variance, a strong asymmetry with respect to radial wind at 36.5° incidence is found. This asymmetry is much more pronounced than up-to-downwind asymmetry for the Normalized Radar Cross Section (NRCS).
Taking advantage of exceptionally continuous HH acquisitions by Sentinel-1B wave mode, we also present preliminary results for HH polarization as well as dual-polarizations' comparisons. In general, HH shows similar features to VV at each incidence angle. However, both spectral magnitude and imaginary part are larger for HH than those for VV for given incidence and radial wind, which could be explained by larger tilt modulation for HH polarization.
As a signed quantity, the imaginary cross-spectra of short radial waves can be considered to be a parameter strongly correlated with the Doppler Centroid Anomaly (DCA). Indeed, both parameters are directly linked to the time evolution of the detected sea surface scatters. As such, both parameters shall closely trace the wind direction within a single SAR imagette. Yet, Sentinel-1 DCA is, today, unfortunately unreliable, with large latitudinal variations for given surface winds. Free of geometrical configuration, the imaginary cross-spectra can thus serve to replace the DCA estimate to help constrain the retrieval of wind field at moderate to high spatial resolution.
Investigation of Upper Ocean Response to Typhoon Using Wind Field from C-band Dual-Polarization SAR
1Nanjing University of Information Science & Technology, China; 2Nanjing University of Information Science & Technology, China; 3Laboratoire d’Oceanographie Physique et Spatiale, Ifremer, Plouzané, France; 4Second Institute of Oceanography, SOA, Hangzhou, China; 5University of Miami/CIMAS and NOAA/AOML, Miami, USA
Conventional VV-polarized NRCS is saturated as wind speed approaching typhoon intensity. In view of this, high wind speeds are underestimated by CMOD5.N especially in the typhoon eyewall regions. Compared to VV-polarization, NRCS in VH polarization is more appropriate to retrieve high wind speeds with cross-polarized retrieval model such as C-2PO or C-2POD. However, cross-polarization wind speed retrieval models overestimate low and moderate winds. Typhoon has capacity of inducing strong dynamical and thermal impacts on the ocean. During the passage of a typhoon, surface wind stress generates intense turbulence and currents in the upper ocean. In general, CSFR data are used as a wind forcing to simulate ocean surface and subsurface response to the typhoon, while the coarse resolution of CSFR can not accurately depict fine structure characteristc of typhoon. Furthermore, there are obvious difference between typhoon intensity and eye center location from CSFR data and satellite observations.
In order to obtain reasonable wind speeds in typhoon eye and eyewall regions as well as in periphery areas, we build a cost function both involving VV and VH-polarization SAR observation. Co- and cross-polarization wind speed retrieval models, CMOD5.N and C-2POD, can yield simulated NRCS in VV and VH poalrizations. The initial first guess wind field is not dervied from numerical weather prediction model, but VH-polarized SAR image itself. According to wind steak features appearing on the typhoon SAR images, we first extracted wind directions by using local gradient method and two-diemensional interpolation technique.The retrieved wind directions are compared with HWRF simulations and WindSat measurements. Subquently, we use C-2POD model and VH-polarized NRCS to retrieve wind speeds. As a result, the initial first guess u and v components can be estimated by using retrieved wind speeds and wind directions. The optimum wind vector estimate for any given wind cell will therefore correspond to a minimum in the cost function.
We use the Regional Oceanic Modeling System (ROMS) to simulate characteristics of upper ocean response to the typhoon. The SAR-derived wind fields are used to force the ROMS. The model outputs reveal the sea surface temperature (SST) cooling and sea surface salinity (SSS) augment on the righ side of the typhoon track. The decrease of SST and increase of SSS are caused by the fact that the entrainment of cold and high salt water breaks through the thermocline and gets into the mixed layer and surface. We compare SST and SSS simulations with microwave Optimally interpolated SST products and SMAP SSS data. Moreover, we also use ROMS simulate the mixed layer depth and upwelling velocity during the passage of the typhoon. Results show the deepening of the mixed layer and increase of the upwelling velocity due to the typhoon-induced vertical mixing. We analyze NPP VIIRS-derived chlorophyll concentration before and after the passage of typhoon, and catch sight of obvious chlorophyll bloom. The increase of clorophyll concentration provides us with evidence for the cold water uplifting. The typhoon pumped cold water from the lower layer with rich nutrients which enhanced the surface biological production.
Investigation on the variations in the Secchi disk depth in the eastern China seas in 2002-2016 using MODIS aqua data
1Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences; 2Institute of Marine Instrument Research，Shandong Academy of Sciences; 3School of Oceanology, Shandong Univeristy; 4CNR-ISMAR, Consiglio Nazionale delle Ricerche, Italy
Secchi disk depth (SDD, m-1), which can reflect the clarity and turbidity of coastal seawater, is an important parameter to describe the optical properties of water. In this work, an empirical model for SDD retrieval was established on the basis of the MODIS Rrs data and the in-situ SDD data which were collected in the Yellow Sea and the East China Sea. The SDD model was further applied to retrieve the monthly SDD during the period of 2002-2016 for the Bohai Sea, the Yellow Sea, and the East China Sea; and the variations in SDD was first analyzed with the river discharges and the eutrophication indexed by Chl-a. Over the western Yellow Sea which is characterized by "green tides" of floating Ulva spp blooms in the summer since 2007, the variations in SDD were specially analyzed to investigate the effects of "green tides" on the optical environment.
GF-3 SAR ocean wind retrieval and preliminary assessment
1National Ocean Technology Center, China, People's Republic of; 2State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, China, People's Republic of; 3Laboratoire d'Océanographie Physique et Spatiale, Ifremer,France
On August 10, 2016, carrying the first Chinese C-band multi-polarization SAR, Gaofen-3 (GF-3) satellite was successfully launched into a polar sun-synchronous orbit of 755 km altitude with an inclination of 98° and 26 days repeat cycle. Following several months of on-orbit commissioning phase, GF-3 SAR images have been in operation since January, 2017. As one of the primary users, the State Oceanic Administration (SOA) is operationally conducting GF-3 SAR ocean wind retrieval and plan to officially release the near real time SAR wind products soon. In this paper, we present the first results of GF-3 SAR derived winds and preliminary assessment using the buoy measurements.
In principle, the GF-3 SAR wind inversion methodology is to combine SAR observed NRCS at co-polarized channel with a priori wind information from ECMWF, taking into account that both NRCS observations and models may contain errors. In order to extract the wind speed and direction, the cost function is minimized with the help of look-up table computed from geophysical model function (GMF), making the inversion scheme more efficient.
The coastal winds were estimated from the GF-3 SAR at 1 km resolution in four imaging mode, including Standard Strip, Quad‐Polarization Strip I, Quad‐Polarization Strip II and Narrow Scan imaging mode, and the retrievals are presented. One case of the coastal katabatic wind off U.S. west coast captured by GF-3 is discussed.
The preliminary accuracy assessment of GF-3 SAR wind speed retrievals is carried out against in situ measurements from NDBC buoys. Only the buoys located inside the GF-3 SAR wind cell (1 km) were considered as co-located in space, while the time interval between observations of SAR and buoy was limited to less the 30 min. This criteria yield 38 co-locations during the period from January to April 2017, showing the RMSE of 2.59 m/s. Different performances due to GMF and Polarization Ratio (PR) are discussed. The preliminary results present that GF-3 wind retrievals are encouraging for operational implementation.
|8:30am - 10:00am||C3-ID32397: CAL/VAL of Microwave Data|
|HYDROLOGY & CRYOSPHERE|
Activities in Ground Remote Sensing at IGP-ETH
1ETH, Zurich, Switzerland; 2Swissphoto, Regensdorf, Switzerland
Ground remote sensing by GNSS has been a research topic for the Institute of Geodesy and Photogrammetry (IGP) for some years. In the context of the Hydrology & Cryosphere research of Dragon 4 programme we focus on the determination of the snow water equivalent and of the snow depth. Beside these experimental observations we have been carrying out measurements in order to better assess the propagation of GNSS signals in water. A further interesting, however, not yet really elaborated topic is the measurement of the soil moisture in the frame of landslide hazard monitoring.
In the case of snow water determination we devised a method where GNSS receivers buried in the snow cover are used. From differential measurements between 'snow-free' and 'snow-covered' receivers the water content can be inferred. However, to this end a special refractivity model has been developed and accounted for in the GNSS data treatment. For the determination of the snow height we are mesuring reflected signals in a geometric mode or as applied by different authors, we use the SNR data directly. The propagation through water has been investigated on a dedicated experiment, where we could show the extinction of the signal at roughly 3 cm penetration depth. The water depth can be determined by the geometric analysis of the GNSS signal. Permafrost ground might be a hazard especially if it is located on steep slopes. This is the case in the Alps where Rock Glacier are commonly encountered. The main hazard is due to warm up and to a partial de-freezing. This might be reflected in changing soil/ground moisture. Therefore, the information on this parameter could be one piece of the puzzle in natural hazard assement in alpine areas. We showed, that the temperature and the movements are highly correlated and might even allow for an inversion of the data to determine the sliding horizon.
Soil Moisture Monitoring Using Reflected Signals of BDS GEO Satellites
Beihang University, China, People's Republic of
Soil moisture, the amount of water contained in the soil, is an environmental descriptor that integrates much of the land surface hydrology. From agriculture production to flood and drought prediction, soil moisture plays an important role in human production and human life. Soil moisture monitoring based on GNSS-R technique has been proposed to measure soil moisture using GNSS signals reflected from land surface. It is economical, flexible and able to work all weather and all day. It is a good supplement to current soil moisture observation methods. GNSS signal reflection process over bare land and reflected signal characteristics are explained theoretically. Then retrieval theory is introduced briefly. It can be seen that satellite elevation and azimuth have direct relevance to key parameters involved in soil moisture monitoring, especially surface roughness and antenna gain, which adds complications to the practical application of this technique. Fortunately, BDS GEO satellites have fixed positions relative to earth surface, resulting in constant elevation and azimuth and thus a constant influnce of parameters above. Finally, soil moisture monitoring method using reflected signals of BDS GEO satellites is proposed and its signal processing flow is presented as well. A ground-based experiment was carried out to validate the retrieval method. A RHCP antenna was set up to sky to receive the direct signal while an LHCP antenna was set pointing to the field covered with wheat at initial growth stage. We collected the GPS L1 and BDS B1 signals using a multi-channel GNSS intermediate frequency signal sampler. And the true value of soil moisture was collected by oven drying method once per hour during the experiment period. Then data processing was conducted according to the signal processing flow. Experiment results show an agreement with the true values. Forther more, the results of BDS GEO satellites present a better performance in both accuracy and temporal continuity owing to the fixed position of GEO satellites. We introduce the soil moisture retrieval principle, propose a retrieval method using BDS GEO signals and present the experiment results dedicated to validate method performance. However, priori information of soil composition, surface roughness and antenna gain is needed to obtain a better performance. As result simplified and valid models needs to be further studied. Machine learning algorithms can be applied to this technique, for example.
Characteristics and Limitations of Submerged GPS L1 Observations
ETH Zurich, Switzerland
Extensive amount of water stored in snow covers has a high impact on flood development during snow melting periods. Early assessment of these parameters in mountain environments enhance early-warning and thus prevention of major impacts. Sub-snow GNSS techniques are lately suggested to determine liquid water content, snow water equivalent or considered for avalanche rescue. GNSS antennas are submerged into soil to derive soil moisture. This technique is affordable, flexible, and provides accurate and continuous observations independent on weather conditions. However, the characteristics of GNSS observations for applications within a snow-pack or submerged into water still need to be further investigataed.
The magnitude of the main interaction processes involved for the GPS wavelength propagating through different layers of snow, ice or water is examined theoretically. Liquid water exerts the largest influence on GPS signal propagation through a snow-pack. Therefore, we focus on determining the characteristics of GNSS observables under water.
An experiment was set-up to investigate the characteristics and limitations of submerged GPS observations using a pool, a level control by communicating pipes, a geodetic and a low-cost GPS antenna, and a water level sensor. The GPS antennas were placed into the water. The water level was increased daily by a step of two millimeters up to thirty millimeters above the antenna. Based on this experiment, the signal penetration depth, satellite availability, the attenuation of signal strength and the quality of solutions are analysed. Our experimental results show an agreement with the theoretically derived attenuation parameter and signal penetration depth.
The assumption of water as the limiting parameter for GPS observations within a snow-pack can be confirmed. Higher wetness in a snow-pack leads to less transmission, higher refraction, higher attenuation and thus a decreased penetration depth as well as a reduced quality of the solutions.
In consequence, GPS applications within a snow-pack are heavily impacted by wetness which is even more pronounced during melting period.
Placing the antenna in a fresh water layer as for soil moisture retrievel, a high attenuation of signal strength leads to a signal penetration up to 3.5 centimeter.
In this poster, we present a short introduction to the principle, explain the developed algorithms and show results of experiments dedicated to the signal propagation in water.
|8:30am - 10:00am||D3-ID32278: 3 & 4D Topography Measurement|
|SOLID EARTH & DISASTER RISK REDUCTION|
32278-2 Multi-baselineSAR processing for 3D/4D reconstruction
1LIESMARS ,Wuhan University, Wuhan, China; 2Collaborative Innovation Center of Geospatial Technology, Wuhan, China; 3Key Laboratory of Land Subsidence Monitoring and Prevention,Ministry of Land and Resources, Shanghai, China
InSAR techniques provide researchers a set of tools for topographic mapping, as well as for monitoring deformations on the Earth surface. In Dragon-1 and Dragon-2, our focus was on DEM generation and surface motion estimation with medium resolution InSAR. Since Dragon-3, SAR datasets of high spatial and temporal resolution (TerraSAR-X, COSMO-SkyMed) are available and with the availability of Sentinel-1 data, a global time-series coverage is now reality.
Topographic mapping and surface motion estimation with spaceborne SAR sensors are the main topics of the Dragon-4 project "Multi-baseline SAR processing for 3D/4D reconstruction (id 32278-2)” under the framework of THREE- AND FOUR-DIMENSIONAL TOPOGRAPHIC MEASUREMENT AND VALIDATION (id 32278). In Dragon-4, we work on different test sites investigating the following four topics:
1. Topographic mapping with SAR. We developed a maximum a posteriori (MAP) estimation method for multi-baseline InSAR assisted by StereoSAR. According to Bayesian theory, the combination of StereoSAR and InSAR for topographic mapping can be viewed as update of the StereoSAR DSM with InSAR phase observations. At the same time, the StereoSAR DSM is also a constraint to InSAR phase observations, which can solve the problem of elevation ambiguity and avoid phase unwrapping problems. The Mount Song has been selected as the test area, which is one of the five sacred mountains of China. The experimental result shows that there is neither systematic error nor large data voids in MAP estimated DSM and the standard deviation of height error σh of MAP estimated DSM is less than 10 m with respect to the photogrammetric DEM for the whole area, while in plain areas σh is about 5 m.
2. Urban subsidence analysis. SAR systems can measure distances and movements with high precision. Using for example PS-InSAR, deformations can be estimated with a very high precision. The long-term surveillance of urban subsidence and the infrastructure stability in Shanghai is our major research goal since Dragon-1. With data starting from ERS-1, over ENVISAT ASAR, ALOS PALSAR, up to modern systems like TerraSAR-X, COSMO SkyMed, PALSAR-2, and Sentinel-1, we continuously monitor the subsidence over Shanghai for far over a decade now. The combination of this data and the analysis of the continuous deformation is still on-going. Remarkably, the PS-InSAR precision stays stable over time even using different sensors.
3. Coseismic displacement from Sentinel-1 TOPS data. Terrain Observation by Progressive Scans (TOPS) mode from the Sentinel-1A/B satellites provides up-to-date high-quality Synthetic Aperture Radar (SAR) images over a large coverage, making it widely applied to earthquake studies. Recent work focuses on generation of co-seismic displacement of large earthquakes from Sentinel-1 TOPS images. However, many small/deep/offshore earthquakes have relatively smooth ground displacement disturbed by strong atmospheric influence. The coherence images spanning these earthquakes maybe not desirable e.g. due to the complex topography. Therefore, methods to derive such smooth co-seismic displacements from time-series is needed. We developed a new Sentinel-1 TOPS images analysis strategy with applications to earthquakes occurred recently in China.
High-precision 3D Reconstruction from Synthetic Aperture Radar and Optical Images
1LIESMARS, Wuhan University; 2ifp, University Stuttgart
The reconstruction of topographic information and their changes in the context of our dynamic Earth is one of the main applications of photogrammetry and remote sensing. With advancements in sensor technology and data processing, three-dimensional information can be retrieved in unprecedented precision. With the release of the TanDEM DEM, the DLR released the most precise world-wide DEM, an invaluable data set for numerous applications. The global availability and the high precision are proof of the extra-ordinary capability of Synthetic Aperture Radar (SAR) interferometry (InSAR) for 3D measurements.
With the SAR geodesy concept of the DLR, the radargrammetric measurements are having a comeback. Thanks to the high orbit-precision of TerraSAR-X and TanDEM-X, and by using collateral data to correct the atmospheric delay, absolute 3D positioning precision within a few centimeters is nowadays possible. However, there are several limitations for reaching the maximum precision in SAR geodesy and interferometric SAR. Therefore, a deeper understanding of the underlying error sources is necessary to fully use the potential of the aforementioned methods.
With the rapid developments in photogrammetric computer vision the multi-view photo-consistency measures for dense and accurate 3D reconstructed evolved and based on developments like semi-global matching for multi-view-stereo, photogrammetry reaches relative height precisions in the centimeter domain, comparable to or even outplaying LiDAR.
In this context, the Dragon-4 project “Topographic Mapping - Validation (32278-1)” is working on the three- and four-dimensional high-precision measurement using SAR and photogrammetry. Currently, we are working on three main objectives:
With the recent progress in the three-dimensional measurement precision of photogrammetry and SAR, four-dimensional time-series measurements for surface motion estimation can become possible offering alternatives to differential interferometry based methods. This is especially beneficial, because these methods can be used as supplement to differential interferometry and derived methods, because they are especially applicable for fast surface motions that are otherwise especially difficult to be measured.
Temporal Decorrelation analysis of TropiScat
1Politecnico di Milano, Italy; 2Wuhan University, China
In this paper, we provide a better understanding of temporal decorrelation of tropic forest from TropiScat in various timescales. TropiScat is a ground-based campaign operated at the Paracou field station, French Guiana since October 2011, which allows gathering the tomogram of the forest in all polarizations at P band with a temporal sampling of 15 minutes . To analyze the temporal decorrelation we evaluate the intensity and coherence of the signal array of 15 transmitting and receiving antenna pairs. The vertical distribution of temporal coherence is obtained by comparing two tomograms acquired at different times. To further understand the temporal decorrelation, we evaluate the coherence between tomogram obtained from antenna pairs of different times and that of the same time. The procedure to produce the tomogram and different tomogram processors will be discussed in the final paper .
Deriving coseismicdisplacement from time-series Sentinel-1 TOPS images spanning earthquakes
1LIESMARS, Wuhan University, Wuhan, China; 2Earth Observatory of Singapore, Nanyang Technological University, Singapore; 3Collaborative Innovation Center for Geospatial Technology, Wuhan, China
Terrain Observation by Progressive Scans (TOPS) mode from the Sentinel-1A/B satellites provides up-to-date high-quality Synthetic Aperture Radar (SAR) images over a large coverage, making it widely applied to earthquake studies. Recent work focuses on driving coseismic displacement of large earthquakes from a pair of TOPS images. However, many small/deep/offshore earthquakes have relatively smooth ground displacement disturbed by strong atmosphere influence. The coherence images spanning these earthquakes maybe not desirable either duo to the complex topography. Therefore, methods to derive such smooth coseismic displacement from time-series analysis is needed. Here we present a novel Sentinel-1 TOPS images analysis strategy with applications to a few earthquakes occurred recently in China.
First is the 5 February 2016Mw 6.4 MeiNong earthquake that occurred in Taiwan. For this case, we take a modified spectral diversity method for coregistration of TOPS images to get a smooth interferogram in which the obvious phase jumps are well corrected. Then we take time-series analysis using TOPS images acquired before and after the earthquake to improve the derived coseismic displacement. The results are validated with GPS data near the epicenter area.
Another case includes a series of M<7 earthquakes occurred on the Qinghai-Tibet plateau, To study these earthquake, we collect time-series Sentinel-1 TOPS images acquired before and after earthquakes. We improve the time-series TOPS data processing chain to estimate the coseismic displacement on detected persistent scatters. Our results show that the temporally uncorrelated atmospheric signal can be largely reduced and the subtle coseismic displacement signal can be derived more precisely than single interferogram.
High Precision DSM Generation in Mountainous Areas with Multi-Baseline InSAR
1LIESMARS, Wuhan University, Wuhan, China; 2Collaborative Innovation Center of Geospatial Technology, Wuhan, China
Synthetic Aperture Radar Interferometry (InSAR) is a powerful tool for large-area topographic mapping due to its capability of all-time all-weather imaging and high sensitivity to terrain relief. However, there is an inherent contradiction between geometric decorrelation and sensitivity of height measurement for topographic mapping with a single InSAR pair. A normal baseline of proper length is required to keep a balance between the two issues. A promising solution to this problem is the so-called multi-baseline InSAR analysis. The basic principle of multi-baseline InSAR is to derive an optimal height estimate by joint analysis of multiple phase measurements from several interferograms with different normal baselines. Compared with single-baseline InSAR, the major benefit of using multi-baseline observations is the possibility of exploiting redundant topographic phase observations with different height of ambiguities to improve the accuracy of phase unwrapping, or even avoid phase unwrapping.
In this study, after the analysis and discussion of the probability distribution of interferometric phase, we propose a maximum likelihood (ML) estimation method assisted by SRTM DEM data for multi-baseline InSAR topographic mapping. Based on our method, a spaceborne data multibaseline InSAR processing flow is established. In order to well adapt it to the repeat-pass interferometric pairs, the processing flow integrates the atmospheric effect correction method to improve the reliability of multi baseline estimation. The simulation experiments were designed to test the effectiveness of the maximum likelihood height estimation method and atmospheric effect correction method. The proposed multibaseline InSAR processing flow was applied in ALOS/PALSAR dataset covering Mount Tai area, China. The accuracy of resultant DEMs at spatial resolution of 20 m is evaluated by using a standard Chinese national DEM of scale 1:10,000 as reference. The results show that multi-baseline InSAR can improve DEM accuracy compared with single-baseline case. The quality of multi-baseline InSAR DEM can meet the American DTED-2 standard.
|8:30am - 10:00am||E3-ID32396: Degradation Surveillance of Drylands|
|LAND & ENVIRONMENT|
Exploring hysteresis of land condition trends: China drylands
1CSIC, Spain; 2CAF, China; 3CAS, China
Hysteresis refers to the asymmetric path between to alternative states. Specifically, we apply the concept to analyse differences between degradation and regeneration processes, a phenomena pointed out in the dynamics of several ecosystems . The topic is quite relevant for the ongoing debate about the irreversibility of desertification, challenged by different studies that support re-greening in degraded areas .
It is possible to deduce the existence of hysteresis through the speed of the aforementioned opposed processes. For that, a statistically sound analysis based on 2dRUE results  has been implemented. Previously, 2dRUE was applied to assess land condition in China Drylands using time series NPP data computed from Envisat Meris images . The method incorporates a stepwise regression to signify the effects of time and aridity on vegetation. This allows distinguishing if biomass changes are explained by the impact of wet and dry years, or by land degradation itself. In this way, 2dRUE supplies standard partial regression coefficients, an explicit and untainted measure of changes in land condition.
We have selected the Mann-Whitney U test to compare two variables: Positive and negative time regression coefficients, i.e. regeneration and degradation do not related with aridity fluctuations. The null hypothesis is that both processes happen at the same rate. Data is divided into 3 categories, each one with a different number of classes, Land-use (20); 2dRUE Assessment (8); FAO Aridity (3). Exploratory results show that in half the cases there are significant differences between the speed of degradation and regeneration. In most of them, the pace of regeneration is higher than degradation. Forthcoming works require a detailed insight within those significant categories in aim to interpret the scope of our preliminary results.
Identification of Land Degradation by Coupling Vegetation and Climate based on Remote Sensing Data
1Chinese Academy of Forestry, China, People's Republic of; 2Arid Zone Research Station, Spanish Council for Scientific Research, Almeria, Spain
Land degradation is a process by which the land productive capacity declines or even is completely lost under the influence of natural forces and human activities. The scope of land degradation has become global in the last decades, which compromises sustainable land management and threatens the safety of food production, especially in the poverty-stricken areas of developing countries. Desertification is one kind of land degradation and mainly occupied in arid, semi-arid and semi-humid areas. China is one of the most seriously affected countries by desertification. By the end of 2014, the desertified land area of China was 2.61×106km2. Post-hoc mitigation approaches are expensive and often ineffective. Therefore early warning systems based on Earth Observation make the most accepted scientific basis for controlling land degradation.
With the development of remote sensing technology, long time series remote sensing data have been available for land degradation assessment and monitoring, and the vegetation indicators, such as the NDVI, NPP, Vegetation coverage and biomass were commonly used. However, time series vegetation index will fluctuate severely due to the impact of climate change, especially the fluctuation of annual precipitation, thereby the land production capacity could not be determined accurately.
Therefore, to solve the problem, Xilin Gol League, In+-ner Mongolia Autonomous Region, China, where the land degradation is prevailing in the first decade of the 21st century was selected as the study area. Based on the annual NPP dataset estimated by 10-Day composite NDVI from Envisat-Meris data at 1.2km resolution during 2003 to 2013 and the same period meteorological raster dataset, a new Moisture-responded Net Primary Productivity (MNPP) method, for identifying areas of land degradation based on the change of annual NPP and MNPP over time and Moisture Index (MI) was developed. It was expected that provide technical support and scientific reference data for land degradation assessment and monitoring in study area, even in the whole drylands in China.
Nonlinear Spectral Mixture Effects for Photosynthetic/Non-photosynthetic Vegetation Cover Estimates of Typical Desert Vegetation in Western China
1School of Remote Sensing and Information Engineering, Wuhan University, Wuhan, China; 2Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, China; 3Institute of Forest Resources Information Technique, Chinese Academy of Forestry, Beijing, China; 4State Key Laboratory of Desertification and Aeolian Sand Disaster Combating, Gansu Desert Control Research Institute, Lanzhou, Gansu
Desert vegetation plays significant roles in securing the ecological integrity of oasis ecosystems in western China. Timely monitoring of photosynthetic/non-photosynthetic desert vegetation cover is necessary to guide management practices on land desertification and research into the mechanisms driving vegetation recession. In this study, nonlinear spectral mixture effects for photosynthetic/non-photosynthetic vegetation cover estimates are investigated through comparing the performance of linear and nonlinear spectral mixture models with different endmembers applied to field spectral measurements of two types of typical desert vegetation, namely, Nitraria shrubs and Haloxylon. The main results were as follows. (1) The correct selection of endmembers is important for improving the accuracy of vegetation cover estimates, and in particular, shadow endmembers cannot be neglected. (2) For both the Nitraria shrubs and Haloxylon, the Kernel-based Nonlinear Spectral Mixture Model (KNSMM) was the best unmixing model. In consideration of the computational complexity and accuracy requirements, the Linear Spectral Mixture Model (LSMM) could be adopted for Nitraria shrubs plots, but this will result in significant errors for the Haloxylon plots because of the stronger nonlinear spectral mixture effects. (3) The vegetation canopy structure (planophile or erectophile) determines the strength of the nonlinear spectral mixture effects. Therefore, nonlinear spectral mixing effects for Nitraria shrubs and Haloxylon were validated to be different, additional research is necessary to validate their performance from the canopy to the landscape scale.
|10:00am - 10:30am||Coffee Break|
|10:30am - 12:00pm||A3-ID32301: GHGs from Space|
|ATMOSPHERE - CLIMATE - CARBON|
Validating Space-Based CO2 Observations with surface measurement
1Institute of Atmospheric Physics, Chinese Academy of Sciences, China, People's Republic of; 2Finnish Meteorological Institute, Helsinki, Finland
The accuracy requirements of satellite remote sensing of atmospheric composition and, in particular, greenhouse gases are challenging. The validation of the measurements is highly important in the development of satellite remote sensing systems.
The Chinese team has developed XCO2 retrieval algorithm for TanSat Level 2 data processing and has updated it after the successful launch of TanSat in December 22, 2016. The FMI team has carried out validation studies of GOSAT and OCO-2 satellite retrieval results and they plan to contribute to the validation of TanSat observations. To support the satellite validation using FTS observations, AirCore CO2 profile observations at Sodankylä will be used. Both FMI and IAP teams will work together to verify and investigate the precision of the retrieval results.
Evaluating Space-Based CO2 Observations over China
1Earth Observation Scienfc Group, University of Leicester, United Kingdom; 2School of GeoSciences, University of Edinburgh, United Kingdom; 3Key Laboratory of the Middle Atmosphere and Global Environmental Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
It is well established that the increase in atmospheric concentrations of CO2 and CH4 due to anthropogenic activities is a major driver for climate change. However, our understanding of the role of natural and anthropogenic contributions to the carbon cycle within a dynamic Earth system is still insufficient which leaves predictions of our future climate uncertain.
We have now access to dedicated satellite observations of atmospheric CO2 and CH4 concentrations which provide us with densely sampled data over regions poorly sampled by surface networks. This allows us to critically test and evaluate models of the carbon exchange for key regions such as China.
Currently, three CO2 satellite sensors are in orbit, JAXA’s GOSAT, NASA’s OCO-2 and the Chinese TanSat mission, which gives us an unique opportunity to intercompare observations from multiple space-based CO2 datasets over China and to use them jointly to assess model calculations.
Overview of Activities Related to Remote Sensing of Greenhouse Gases at the Finnish Meteorological Institue and Plans for TanSat validation
1Finnish Meteorological Institute, Helsinki/Sodankylä Finland; 2Institute of Atmospheric Physics, Chinse Academy of Sciences, Beijing, China; 3University of Leicester, Leicester, United Kingdom
Due to the anthropogenic greenhouse gas emissions our climate is changing. Climate forecasts are needed so that we can prepare, mitigate and adapt to the changing climate. The high northern latitudes are especially sensitive to climate change. The quantification and monitoring of the carbon cycle processes are crucial for the understanding of climate system feedbacks. Recently launched satellite instruments mesuring greenhouse gases provide important information related to the carbon cycle processes that can jointly be analysed with ground based observations and compared/combined with modeling. In this presentation we discuss recent recearch activities that have taken place at the the Finnish Meteorological Instiute related to satellite observation of greenhouse gases. Moreover, we present our plans to participate in the validation of Chinese TanSat satellite’s carbon dioxide observations using ground based instruments at Sodankylä as well as our plans on using the TanSat data for studying spatial and teporal variability of carbon dioxide and emisison regions.
The Atmospheric Carbon Dioxide measurment over China from space
1Institute of Atmospheric Physics, Chinese Academy of Sciences, China, People's Republic of; 2Earth Observations Science Group, University of Leicester, Leicester, UK; 3School of GeoSciences, University of Edinburgh, Edinburgh, UK
Atmospheric Carbon dioxide (CO2)is one of the major anthropogenic greenhouse gas that remains significant uncertainties in global carbon cycle and climate change studies. Hyper spectral near infrared and shortwave infrared (NIR/SWIR) measurement from space could provide global column-average CO2 dry-air mixing ratio (XCO2) in advanced accuracy and precisions to reduce the uncertain of climate prediction. After the Greenhouse gas monitoing satellite including GOSAT and OCO–2 from USA-NASA and Japan-JAXA, China’s carbon dioxide observation satellite (TanSat) has been successful launched in 2016. TanSat is a carbon dioxide observation satellite funded and supported by the Ministry of Science and Technology of the People’s Republic of China and the Chinese Academy of Sciences. The TanSat retreival algorithm has been developed to approeach the XCO2 in a highly accuracy and precision reqiurment. The TanSat algortihm has been applied on GOSAT (ATANGO) and OCO-2 measumrent and well optimaized before it applied in TanSat operational data processing. The retrieval algorithm and its perfomance over China has been studied. The ATANGO data product has been used in carbon flux inversion in China.
Direct observation of anthropogenic CO2 signatures from OCO-2
Finnish Meteorological Institute, Finland
Anthropogenic CO2 emissions from fossil fuel combustion have large impacts on climate. In order to monitor the increasing CO2 concentrations in the atmosphere, accurate spaceborne observations—as available from the Orbiting Carbon Observatory-2 (OCO-2)—are needed. This work provides the first direct observation of anthropogenic CO2 from OCO-2 over the main pollution regions: eastern USA, central Europe, and East Asia. This is achieved by deseasonalizing and detrending OCO-2 CO2 observations to derive CO2 anomalies. Several small isolated emission areas (such as large cities) are detectable from the anomaly maps. The spatial distribution of the CO2 anomaly matches the features observed in the maps of the Ozone Monitoring Instrument NO2 tropospheric columns, used as an indicator of atmospheric pollution. The results of a cluster analysis confirm the spatial correlation between CO2 and NO2 data over areas with different amounts of pollution. We found positive correlation between CO2 anomalies and emission inventories. The results demonstrate the power of spaceborne data for monitoring anthropogenic CO2 emissions.
Chinese CO2 Fluxes Inferred From OCO-2 and GOSAT and From In-situ Data During the 2015 El Niño Event
1Key Laboratory of Middle Atmosphere and Global Environment Observation,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing,China; 2National Centre for Earth Observation, School of GeoSciences, University of Edinburgh, Edinburgh,UK; 3National Centre for Earth Observation, Department of Physics and Astronomy,University of Leicester, Leicester, UK
China represents a significant contribution to global observed variations of atmospheric carbon dioxide (CO2) due to its large landmass, and its high fossil fuel emissions associated with unprecedented economic growth. We report CO2 fluxes in 2014 and 2015 inferred, using an ensemble Kalman Filter [Feng et al, 2009], from data collected from five new regional background ground-based sites over China (together with available NOAA sites), and fluxes inferred from OCO-2 (version 7) and GOSAT (UoL v7) XCO2 data. We find that the resulting posterior CO2 concentrations are generally consistent with independent validation data downwind of the Chinese mainland. To better understand the response of the Chinese biosphere to the 2015 El Niño we compare the magnitude and distribution of CO2 fluxes inferred from different data sets. We find that the net CO2 emissions over China inferred from GOSAT and OCO-2 XCO2 retrievals are higher than those from the in-situ data. Our results highlight the importance of space-based observations for top-down flux inversions. Chinese TanSat project, together with existing and planned missions, will significantly improve flux estimates over China.
Error Analysis for Space-borne IPDA Lidar Measurement of Atmospheric CO2
1Key Laboratory of Atmospheric Composition and Optical Radiation, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences; 2University of Science and Technology of China
CO2 is a long-lived trace gas which acts as the most important greenhouse to the global climate. For its short-wavelength transparent and long-wavelength absorbed characteristic, the increase of CO2 caused by human activities induces global warming and a series of climate changes since the industrial revolution. Although it is almost well-mixed in the atmosphere, CO2 mixing ratio varies with time, decreases with altitude, and spaces between sources and sinks, the temporary emissions such as fires and burning occurring near the surface on regional scale changing CO2 mixing ratio sharply and damped by atmospheric transport and diffusion in a short time. It is necessary to infer the spatial distribution of carbon sources and sinks distribution with repeated CO2 measurements on a large scale, and this requires very demanding measurement accuracy to the relative small variation of CO2 in the atmosphere. A stringent precision of space-borne CO2 data, for example 1 ppm or better, is required to address the largest number of carbon cycle science questions. A high measurement sensitivity and global covered observation is expected by space-borne IPDA (Integrated Path Differential Absorption) lidar which has been designed as the next generation measurement. By selecting the absorption features of the lidar operating wavelength appropriately, IPDA lidar could obtain the dry air total column CO2 mixing ratio named XCO2 by compared two echo pulse signals reflected from the Earth with a high weight to the boundary layer. In this paper an assessment is made to describe the various error sources limiting the accuracy and precision of the measurement. An overview is presented of the relative contribution of each error source including the inadequate knowledge of the atmosphere pressure and temperature, surface reflectivity, reflected surface elevation, and errors from lidar system such as shot noise, dark noise and spectral purity. A global simulation is used to investigate the sources of errors associated with the configurations of lidar system and the environment parameters. The simulation is carried out over global scale with atmosphere pressure and temperature from NCEP, surface elevation model and surface reflectivity from MODIS, and the CO2 distribution is from OCO-2 dataset. The results identifies that surface albedo plays an important role in the process of satellite remote sensing. It may be inferred that errors impacted by reflectance of the Earth vary with seasons. This would need an improved acknowledge on seasonal variations of surface reflectivity and provide a guidance for improving the accuracy of space-borne IPDA detection.
|10:30am - 12:00pm||B3-ID32281: Ocean and Coast Sustainability|
|OCEANS & COASTAL ZONES|
Arctic Sea Ice Monitoring By Multiple Spaceborne SAR
1German Aerospace Center – IMF-SAR BF; 2Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China, People's Republic of; 3University of Chinese Academy of Sciences
Arctic region is experiencing faster warming than that in the middle and low latitude region, which triggers extensive change of physical and biological Arctic systems. Sea ice, as one of the most important indicator of climate change in Arctic, is showing an accelerating declination trend. The loss of sea ice in the Arctic is not only a simple outcome of climate change, but it also has strong feedback to regional and global climate. In addition to the climate change issue, Arctic is being paid more attentions than ever before, as increasingly accessible for extensive shipping (e.g., the recently opened Northern passages in summer) and oil and gas exploration. Satellite observation have been exploited for Arctic sea ice monitoring for more than a few decades, as they have advantages of large coverage and flexible acquisitions. In contrast to optical imaging, microwave sensors are not impeded by cloud coverage or lack of daylight. Among the microwave sensors, Synthetic Aperture Radar (SAR) has unique advantages of high resolution, as well as large coverage.
For Arctic sea ice monitoring, in the first step, we focus on deriving static and dynamic information, e.g., classification of ice types, ice-water discrimination, ice concentration and drift of sea ice. We will present our recently collaboration on deriving such information based on C- and X-band SAR, including TerraSAR-X, Radarsat-2 and the Chinese recent launched GaoFen-3 (GF-3). Different algorithms and approaches have been developed for these spaceborne SAR data derive sea ice information. In particular, the SAR data acquired in multiple polarizaiton are exploited. In addition to derive sea ice information from SAR data, we will also present some preliminary studies on interaction of swell and ice in the marginal ice zone (MIZ).
On imbalance problem in a fully automatic SAR oil spill monitoring system
Ocean University of China, China, People's Republic of
A fully automatic SAR oil spill monitoring system briefly consists of three parts, 1) dark target segmentation on SAR image 2) dark target feature extraction 3) dark target classification. In order to build a fully automatic system with high detection and high classification performance, the first step requires all oil spill targets to be extracted in the first step, the second step requires the category distinction of dark targets in the feature space to be as high as possible to reduce the classification complexity and the third step requires the classifier to deal with imbalance problems.
The classification complexity can be simply expressed as the size of the overlapping regions of the distribution of the two types in the feature space. The larger the overlap, the more difficult it is to train a high performance classifier. The negative effect of imbalance is equivalent to a multiplicative amplification factor attached to the complexity. The imbalance problem would disappear if complexity is reduced zero. However, the complexity is impossible to be zero, therefore the technical effort to build a high performance automatic oil spill monitoring system is to try to reduce classification complexity and to deal with imbalance problem.
In order to ensure that all oil spills are extracted, the existing segmentation algorithm for extracting dark targets from SAR images will lead to a large number of look-alikes appear, which contain not only dark targets caused by common atmospheric or oceanic phenomena, but also lots of unexplained ones. That is the source of the imbalance problem. In the segmentation stage, an adaptive threshold segmentation algorithm based on multi-scale background normalization is adopted at first to ensure that all oil spills are extracted, and then a post-processing filter chain is used to reduce the imbalance of the targets from 1:100 to n1:5 below.
77 features collected from different researchers are used to improve the category distinction of the types in the feature space, that is, to reduce the complexity of the classification problem. The more the features, the more weights the network needs to adjust, therefore the more training samples are required. However, all 77 features are still used in our study since there are sufficient samples available and computation amount is not so high. Some wrong category labels of samples due to human error may increase classification complexity, especially in the case of a large number of samples. By using an iterative sample category designation method combined with manual classification and machine classification, the number of error labels is significantly reduced and thus the classification complexity is reduced either.
Double-hidden-layer neural network has strong capability to fit complex decision surface, but it also easy to fall in over-fitting and suffer high false discovery rate under the circumstance of imbalance. The Adaboost integrating multiple double-hidden-layer neural networks plays a role in smoothing the decision surface, thus weakening the over-fitting effect and enhancing the generalization performance of the classifier. Moreover, Adaboost trends to reduce the false alarms in imbalance condition since its component classifiers pay more attention on the samples misclassified by the preceding ones. Therefore the Adaboost based on neuronal network has capability to deal with the imbalance problem.
By applying the techniques mentioned above, a fully automatic SAR oil spill monitoring system with detection rate of 81%, false discovery rate of 17%, false alarm rate of 5% and correct recognition rate of 92% is obtained for the sample set consisting of 23768 dark targets extracted from 337 scences of Envisat ASAR and Cosmo-SkyMed images.
Two thresholds determination for Ulva Prolifera bloom coverage estimation in the Yellow Sea
Ocean University of China, China, People's Republic of
In 2008, an extensive Ulva Prolifera bloom occurred in the Yellow Sea (YS) just before the Olympic Sailing Regatta and draw much attention of the world. Then Ulva bloom annually occurred in the YS each summer and attracted the interest of the ocean remote sensing and marine biologist community. Wide swath and short re-visit time optical satellite data were first utilized to monitor the Ulva bloom and estimate their coverage area using methods such as NDVI and FAI. However, the estimated Ulva bloom coverage area were very different in the published literature mainly due to adopted different thresholds T0 and T1. T0 was used to differentiate the algae-containing pixel with seawater pixel while T1 was used to differentiate algae full-covered pixel with partial-covered pixel. In this study, those two thresholds were further studied.
Threshold T0 was derived as follows: (1) First, generate the FAI and FAI gradient image for each optical satellite imagery; (2) classify all pixels in the satellite image as seawater pixel and non-seawater pixels based on the FAI gradient image;(3) replace non-seawater FAI values with median FAI of the neighboring seawater pixels to construct the seawater FAI background image; (4) generate seawater-removed FAI image by subtracting the seawater FAI background image from the FAI image, where pixels greater then zero will be algae pixels.
In the recent study, the author developed the Ulva bloom biomass estimation model and found that (1) FAI threshold T1 was significantly underestimated in the former study (2) FAI linearly increased with the increase of algae coverage but increased slowly after algae completely covered, thus the turn-point in the FAI-biomass curve was the FAI threshold T1. In this study, the lookup table of threshold T1 for specific satellite sensor were simulated in different sun/sensor viewing geometry and atmospheric conditions based on the filed measured algae spectrum.
The high-resolution satellite data were used to validate the results in this study. (1) The Ulva bloom coverage estimated from MODIS data and concurrent high-spatial resolution Chinese GF-1 WFV data (16m) were compared with the relative difference 10%. (2) The threshold T1 was validated with high-spatial Worldview-2 satellite data.
This method can be implemented to OLCI/Sentinel-3 data and the subsequent estimation Ulva bloom coverage from OLCI data will be conducted in this summer.
Incidence angle normalization of Sentinel-1 Wide and Extra Wide Swath data for oceanic applications
University of the Aegean, Greece
Synthetic aperture radar (SAR) imagery provides an effective source of data for observing, measuring and quantifying oceanographic phenomena. The ability of SAR sensors in retrieving data in almost all weather conditions, independently of sunlight illumination, is an extremely useful aspect, important for oceanographic applications. The quality of SAR imagery is dependent on the mode of acquisition and raw data processing. SAR data acquisition techniques introduce a significant backscattering trend in the range direction of the received signal. In Wide Swath and Extra Wide Swath modes, results in a progressive reduction of brightness over images from near to far range, introducing errors on the detection and classification of dark features to oil spills and lookalikes. The present research, aims to examine normalization techniques previously applied to ENVISAT SAR Wide Swath data. We investigate possible methods for limiting the issue of Normalized Radar Cross-Section (NRCS or σ°) variation, due to the incidence angle variations in Sentinel-1 Wide and Extra Wide Swath and data. NRCS depends on the relative azimuth angle between the radar look direction and wind direction. At low incidence angles over a certain wind speed and direction NRCS values are different from these at high incidence angles. In order to eliminate errors during image processing and analysis for oceanographic feature extraction, a normalization is required to limit the NRCS variation over the various incidence angles is suggested. Based on previous studies, the most widely used incidence angle correction technique is the square cosine correction. However, the square cosine correction is valid for surfaces with Lambertian reflectance properties and is not expected to perform in a satisfactory way over the sea. Here we apply two sensor independent functions aiming to improve the dark object detection in SAR imagery over ocean: a theoretical backscattering shape function which is derived from a minimum wind speed and an empirical range fit of NRCS against incidence angle θ. The former method exploits only the modelled NRCS values, while the latter only the image content. The aim of this paper is to apply a simple but consistent scheme for reducing the dynamic range of SAR images by removing the mean incidence angle dependence. The approach targets to normalize the Wide and Extra Wide Swath SAR image to a fixed reference angle. From the approach a single global threshold is applied to detect dark objects in SAR imagery.
Detection and Tracking of Offshore Platform’s Oily Slicks in TerraSAR-X Imagery
1German Aerospace Center (DLR), Germany; 2Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China; 3University of Chinese Academy of Sciences, China
The pollution of the marine environment due to deliberate discharge of untreated ballast waters is not only an operational procedure done by ships but also by offshore platforms. Although, the amount of oil released into the ocean by the offshore platforms using this procedure on one-time basis is derisory, if compared with the massive spill event in case of platform accidents like the Montara and Deepwater Horizon, the long term damages on the flora and fauna are severe.
As the North Sea is characterized by fairly shallow water bathymetry, it has been extensively exploited in the past years for oil extraction and production. By now, it hosts a significant number of offshore installations and therefore the probability of minor leaks is quite high. A large number of Synthetic Aperture Radar (SAR) images are being acquired and processed operationally over North Sea platform installations for potential oil pollution using the TerraSAR-X satellite . The ScanSAR and WideScanSAR mode in VV polarization imagery have been preferred due to large coverage and higher oil-water contrast. Among the dataset collected, a constant leakage from the platforms belonging to the Forties oil field has been observed.
Thanks the low TerraSAR-X orbit altitude and relatively high latitude location of the Forties oil field, leaks from the same platforms have been observed with temporal interval of less than 13 h. While most previous studies on tracking oil spills assume that the observed slicks by consecutively acquired SAR images are the same and spatial displaced by the drift effect , a completely different situation is outlined by the analysis in . By model simulation it is shown that leaks were not start-stop but continuous with only part of the old oil being drifted.
 S. Singha, D. Velotto, and S. Lehner, “Near real time monitoring of platform sourced pollution using TerraSAR-X over the North Sea,” Mar. Pollut. Bull., vol. 86, no. 1–2, pp. 379–390, Sep. 2014.
 Y. Cheng et al., “Monitoring of Oil Spill Trajectories With COSMO-SkyMed X-Band SAR Images and Model Simulation,” IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens., vol. 7, no. 7, pp. 2895–2901, Jul. 2014.
 X. M. Li, T. Jia, and D. Velotto, “Spatial and Temporal Variations of Oil Spills in the North Sea Observed by the Satellite Constellation of TerraSAR-X and TanDEM-X,” IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens., vol. 9, no. 11, pp. 4941–4947, Nov. 2016.
|10:30am - 12:00pm||C3-ID32439: MUSYCADHARB (part 1)|
|HYDROLOGY & CRYOSPHERE|
Response of Snow and Glaciers to Climate Variability: Integration of Satellite Data Products and Atmospheric Model Variables
1TU Delft, Netherlands, The; 2State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, P.R. China; 3ICube Laboratory, UMR 7357 CNRS-University of Strasbourg, 300 bd Sébastien Brant, CS 10413, F-67412 Illkirch Cedex, France; 4Institute of Tibetan Plateau Research, Chinese Academy of Sciences, China
Glaciers on the Tibetan Plateau are the main reservoirs of water in the region and much attention is being given to monitor the response of these glaciers to climate variability. Climate forcing varies across the Plateau with the westerlies from inner Eurasia and monsoons from India and East Asia. The surface properties of glaciers characterize the interaction between the atmospheric boundary layer and glaciers. Traditionally, the surface properties of glaciers are observed in situ, but on the Plateau the spatial and temporal variability of such properties cannot be captured by in – situ experiments only. Our main goal is to characterize the surface energy balance of glaciers using a suite of measurements by space – borne observing systems.
Building upon the work done in the previous Dragon investigations, during this 1st Dragon 4 year we focused on the following aspects:
Time series of data products on albedo and net radiation were analyzed to assess the variability in space and time of albedo in glacial areas and to document the corresponding impact on net radiation. Snowfall leads to sudden and large increase in albedo, which may be as high as 0.8 with deep, fresh now. This leads to a change in net radiation from about 800 Wm-2 to 200 Wm-2, i.e. an extremely large reduction in radiative load, slowing down snow-melting. The same analysis documented a large spatial variability on both minimum, i.e. glacier, and maximum albedo. Such variability is due to a combination of surficial deposit (ice cover) and terrain, which affects irradiance.
The response of glaciers to climate variability was evaluated in different ways, including the retrieval of the glacier surface velocity using image correlation of paired high spatial resolution images (Landsat TM and OLI). This study focused on the Nyainqêntanglha Range and the period from 1993 to 2015. We analyzed wintertime images at intervals of about one year. The analysis of these time series of ice surface displacement, revealed that the observed signals were a combination of a linear trend and a multi-annual component with variable amplitude from place to place.
Surface features, namely roughness, slope and elevation were retrieved with a combination of ICESat/GLAS and ASTER GDEM data to estimate and map the aerodynamic roughness of glaciers. This property modulates fluxes of latent heat (evaporation, sublimation) and sensible heat. The response of the laser waveform to morphology was studied in detail, showing that roughness and slope of the surface can contribute several meters to even several tens of meters to the pulse shape.
The spatial variability of spectral reflectance and albedo within a glacier was evaluated using Landsat TM and GuoFeng multi –spectral images. Areas covered by debris and lakes or ponds linked with a glacier were clearly delineated, particularly using the Guofeng very high spatial resolution images. Differences in spectral reflectance and albedo were rather large and the consequences in terms of spatial variability, within a glacier, of radiative forcing are being evaluated.
The work on time series of glacier albedo revealed large and rapid variations in the radiative forcing on glaciers. These variations are not reproduced by the land surface schemes currently implemented in advanced atmospheric models such as WRF. We have combined WRF snow depth with MODIS albedo to parameterize the dependence of albedo on snow depth and snow age. This parameterization has been evaluated against in – situ measurements at the Plateau permanent observatories.
The parameterization constructed in this way has been implemented in WRF and the sensitivity of the WRF land surface energy balance has been evaluated, showing rather large impacts on both radiative and convective fluxes.
Recent advances in the estimation of water losses with ETMonitor driven by satallite dat
1Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, 100101, China; 2Department of Geoscience and Remote Sensing, Delft University of Technology, 2628 CN Delft, The Netherlands; 3University of Chinese Academy of Sciences, Beijing, 100049, China
One great challenge of cryosphere and hydrosphere science in high elevation regions is the scarcity and sparseness of data on the multiple variables and processes relevant to the understanding of the water cycle.
Quantitative information on water losses is important to understand the global terrestrial water cycle and land – atmosphere interactions. The global evapotrasnspiration in 2008-2013 with a spatial resolution of 1 km was determined using ETMonitor as the sum of the evapotranspiration components, i.e. plant transpiration, soil evaporation, open water evaporation, rainfall interception, snow and ice sublimation. All these variables were retrieved using the ETMonitor model driven by multiple satellite data products. The ASCAT (Advanced Scatterometer) soil moisture data product was applied as a key input to scale ET between 0 and ETmax. To allow the estimation of ET at high spatial resolution, the 0.1° resolution ASCAT data product was downscaled to 1km spatial resolution globally using bilinear resampling method. We have developed a different, bio-phyisical, downscaling procedure applicable for regional studies and based on high resolution surface temperature and vegetation index data products. The estimated water losses agreed well with the in situ tower based observations at a number of FLUXNET sites, with high correlation, low bias, and low root mean square error. The retrieved ET captures the expected global patterns and the details of spatial and temporal patterns were consistent with the current available global evapotranspiration products such as data from GLEAM (Global Land Evaporation Amsterdam Model) and the GLDAS (Global Land Data Assimilation System) Noah product. The ETMonitor data product is superior due to the high spatial and temporal resolutions. We have also experimented with the ESA-CCI (European Space Agency - Climate Change Initiative) soil moisture data product to replace the ASCAT one. A first evaluation was carried out by retrieving ET in China during 2001-2015 and the results used to contribute to the National Remote Sensing Monitoring for Sustanable Devepoment Report in China (2016).
To improve the accuracy of ETMonitor in cold and high elevation regions, the algorithm to estimate snow and ice sublimation was improved, by adapting the Penman – Monteith combination equation. This method was evaluated against eddy – covariance measurements of latent heat flux at high elevation sites in the Heihe river Basin N – W China: on average the RMSE was 8.75 W m-2. We have also evaluated the bulk aerodynamic (BA) method against the same measurements and the BA performance was slightly worse. The main driver of the P – M equation is net radiation, which is very variable at high elevation due to the variability of albedo, which enhances the scope of using satellite observations to estimate and monitor sublimation. A case – study on the upper reach of the Heihe River Basin has been carried out using MODIS data products on surface albedo and temperature.
Work contiuned on improving other algorithms and data products. An algorithm to retrieve the total precipitable water was developed, based on the ratio of brightness temperature changes ΔTb18.7/ ΔTb23.8 , using atmospheric profiles obtained from the globally distributed radiosonde observations and applying a microwave radiative transfer model. This algorithm can retrieve total precipitable water under both clear and cloudy sky condition over land, and can be easily transferred to MWRI on board the FY-3 satellites. To retrieve the surface freeze and thaw condition, an innovative freeze/thaw index based on microwave observations at 18.7 and 36.5 GHz was defined and assumed to be linearly correlated with the radiometric land surface temperature retrieved with thermal infrared observations. It was found that this linear relationship is quite reliable for most areas, and can provide high-resolution information on near surface soil freeze/thaw state. The validation of the high-resolution freeze/thaw state against soil temperature measured at active layer monitoring sites along the Qinghai-Tibet Highway illustrated a moderate accuracy over a decade scale.The daily snow cover fraction at 500m resolution was retrieved in the Tibet Plateau in 2013, and missing values due to the cloud cover were filled to obtain a cloud-free dataset.
The Potential Application of Microwave Product from Global Precipitation Measurement Mission for Soil Moisture Modeling in Mun River Basin, Thailand
Institute of Remote Sensing and Digital Earth, China, People's Republic of
Mun river basin is largest basin in Mekong river region, where both flood and drought frequently occur. Water management by hydrological model is difficult due to lack of accurate and spatial/temporal continuous products to force and localize the model. The new Precipitation and soil microwave products gradually plays important role for hydrological modelling. The study introduced the precipitation product at 0.1 degree spatial resolution (GPM mission) for SM simulation by Variable Infiltration Capacity (VIC) model. Then we assessed accuracy of 10cm soil moisture simulation by comparison with SMAP soil moisture product at a spatial resolution of 9km. The results show that:(1) GPM precipitation can be compared with gauge-based monthly precipitation in Mun river;(2) GPM products can be used to simulate spatial pattern of soil moisture in dry season; the simulated soil moisture has a high accuracy in the upperstream of basin but poor in the downstream due to spatial pattern of irrigation application in Mun river basin. It suggests that based on GPM and SMAP products, we can make model calculation and cross validation by remote sensing technology. Therefore microwave remote sensing products are expected to be introduced for water management in remote or data-lacking regions.
Soil hydrologic parameterization for water balance modelling using remote sensing Land Surface Temperature data
1politecnico di milano, Italy; 2CAS CAREERI, China
Soil hydrologic parameterization, as well known control the energy and water fluxes of hydrologic basin surface playing a crucial role in hydrological model simulation for operative application in the field of water engineering. Despite their importance their definition for large areas is always a source of uncertainty due to difficulty of representative ground measurements , their spatial variability also strongly affected by land use change and agricultural practices.
In the framework of Dragon 4 Project “Forcing, calibration, validation and data assimilation in basin scale hydrological models using satellite data products”, the paper presents a procedure for soil hydrologic parameterization based on the assimilation of satellite LST data into a thermodynamic distributed water balance model (FEST-EWB). The model algorithm solves the system of energy and mass balances in terms of a representative equilibrium temperature (RET), that is the land surface temperature that closes the energy balance equation and so governs the fluxes of energy and mass over the basin domain. This equilibrium surface temperature, which is a critical model state variable, is comparable to LST as retrieved from operational remote sensing data from MOST, ESA and NASA agencies. This approach will be compared with traditional ones based the pixel wise use of pedo transfer function, calibrated for available soil maps.
The case study is the upper part of the Heihe River basin where a consistent historical data set will allow to test this approach.
Parameter estimation for a simple two-source evapotranspiration model using Bayesian inference and its application to remotely sensed estimations of latent heat flux at the regional scale
1Institute of Earth Environment, Chinese Academy of Sciences, China, People's Republic of; 2Key Laboratory of Western China’s Environmental Systems (Ministry of Education), Lanzhou University; 3Key Laboratory of Highway Construction & Maintenance Technology in Permafrost Regions, Ministry of Transport, CCCC First Highway Consultants Co., LTD; 4School of Geographical Sciences, Southwest University
A simple two-source evapotranspiration (ET) model was applied to the Yingke and Daman irrigation districts of the Zhangye Oasis, which is located in the middle reaches of the Heihe River, China. The ET model was composed of two parts, including an evaporation (E) sub-model and a transpiration (T) sub-model. A separated parameter estimation scheme was conducted using Bayesian inference. First, an empirical multiplier was estimated for an E sub-model using observations that were collected after crop harvests. The empirical multiplier was then assigned to the most-likely value in the simple two-source ET model. Second, a global sensitivity analysis was performed to identify the key parameters that were responsible for most of the variability in the λET results within the T sub-model. To avoid equifinality or over-parameterization, Bayesian inference was applied to estimate the key parameters that induced the most variability in the first set. A second set of Bayesian inference was then performed by fixing the most-likely values of these parameters, and the other parameters were defined one-by-one as Bayesian parameters. These parameters were estimated for seven sites. The coefficient of determination for the modeled λET and the observed values exceeded 0.9. Next, a cluster analysis was conducted using the canopy height, leaf area index and soil moisture content to classify the fields with the highest similarities and then to distribute the same parameter values to similar fields. Finally, λET was estimated using the most-likely values of the parameters at the regional scale. The root-mean-square error of the remotely sensed estimates was less than 20 Wm-2, the mean absolute percent error did not exceed 4%, and the correlation coefficient was greater than 0.97. The validation was conducted for both the modeled λET at the point scale and for the remotely sensed λET at the satellite pixel scale. The results demonstrate that using cluster analysis, the most-likely values of the parameters can be effectively applied to estimate remotely sensed λET.
Impact Analysis of Climate Change on Snowfall and Fractional Snow Cover Using Numerical Model and Remote Sensing Product Over Complex Mountainous Region
1Northwest Institute of Eco-Environment and Resources, CAS, China, People's Republic of; 2Northwest Institute of Eco-Environment and Resources, CAS, China, People's Republic of; 3Northwest Institute of Eco-Environment and Resources, CAS, China, People's Republic of; 4The Henry Samueli School of Engineering, University of California, Irvine
The effect of climate change on snow is complicated at regional scale. The high spatio-temporal resolution snow related variables simulated by weather research and forecast model including snowfall, snow water equivalent and physical snow depth and the high spatial resolution fractional snow cover data extracted from MODIS/Terra are adopted to evaluate the effect of climate change on snow over the Heihe River Basin (HRB) in last 15 years using Empirical Orthogonal Function (EOF) analysis and Mann-Kendall / Theil-Sen trend analysis. The results indicate 1) Due to the air temperature increasing, the fractional snow cover, snow water equivalent, physical snow depth over the whole HRB region decrease in last 15 years, especially at the height over 4500 m, however, the snowfall increases at mid-altitude ranges over the upstream of HRB. 2) Over the upstream of HRB, the total snow flux increased, however, the number of snowfall days decreased in last 15 years, so the occurrence of extreme snow events over the upstream of the HRB might increase. 3) The air temperate over the downstream increased at the most of the HRB, however, the snowfall over this region decreased in last 15 years, so the weak ecological system over the downstream may be exacerbated in future.
|10:30am - 12:00pm||D3-ID32294: Hazards in Coastal Regions|
|SOLID EARTH & DISASTER RISK REDUCTION|
The ESA/MOST Dragon IV project: Detection and Interpretation of Time Evolution of Costal Environments through Integrated DInSAR, GPS and Geophysical Approaches.
1Istituto per il Rilevamento Elettromagnetico dell'Ambiente, CNR, 328 Diocleziano, I-80124 Napoli,; 2Key Laboratory of Geographical Information Science, Ministry of Education, East China Normal University, Shanghai 200241, China; 3School of Geographic Sciences, East China Normal University, Shanghai 200241, China; 4Dept. of Earth and Planetary Sciences, McGill University, Montréal, QC, H3A E08, Canada; 5School of Information Science Technology, East China Normal University, Shanghai 200241, China
As the global sea level rises, there is increased concern about the growing urbanization of the low-lying deltaic coastal regions, and the related coastal hazards. Furthermore, the local relative sea-level rise can be significantly affected by vertical ground motions, either due to natural processes (e.g., global isostatic adjustment, tectonics, sediment consolidation and compaction, upstream sediment load reduction) and to human activities (e.g., groundwater extraction, land reclamation, building construction and consolidation). Deformation phenomena can be in the same order of magnitude (or greater) than climate-induced sea level rise. However, coastal ground motions are in practice often poorly known, and in many cases, little information is available about the patterns and time evolution of ground motion. It is, therefore, worth to monitor coastal delta regions through advanced Earth Observation (EO) systems that are capable detecting the ongoing surface deformation phenomena, recovering their spatial extent on the ground and following their temporal variability. This is beneficial for the subsequent interpretation of natural/anthropogenic processes causing surface motion.
The activities of this present Dragon IV project are mostly focused on the analysis of modification processes that characterize two important Delta river areas in China: the Yangtze and the Pearl River Deltas. Both delta regions are significantly affected by sea-level rise and natural/anthropogenic deformation phenomena, making it clear the need of extended analyses for a better understanding of the mechanisms responsible for the observed surface modifications, and for the planning of actions devoted to risk prevention for populations living in coastal areas.
More specifically, the aim is to retrieve long-term displacement time-series from EO data, specifically satellite Synthetic Aperture Radar (SAR), of the investigated areas through advanced differential interferometric synthetic aperture (DInSAR) techniques, as well as to complement DInSAR results with information derived from GPS/leveling campaigns with the aim to perform sound and extended geophysical analyses, and coastal erosion or accretion rates, which will be obtained by jointly exploiting archives of SAR data and the new generation of optical remote sensing systems.
In order to evaluate the combined risk of sea level rise, storm surges, and ground subsidence, the availability of high-resolution digital elevation models (DEM) of monitored coastal areas is mandatory. Added-value EO data products, such as the updated DEMs of coastal areas subject to sea-level rise, the time-series of terrain displacement, mean displacement velocity maps, and time-series of SAR backscattering maps, will be obtained by exploiting archives of SAR data with different levels of spatial resolution spanning a long time interval of about 20 years since the beginning of 2000s to 2020.
During the first year of this present D4 project, some preliminary activities have been conducted for processing Sentinel-1 data on both Delta regions by using different DInSAR tools in such a way to perform combined Small Baseline Subset (SBAS)  and Permanent Scatterers (PS)  analyses. Sentinel 1 time-series span about last three years. However, in order to have the historical perspective of the deformations occurring in the two areas, a few experiments have been carried out to obtain deformation maps covering the time lapse between 2002 to present days using (when available) ENVISAT and Cosmo-SkyMed SAR acquisitions. The latter are worth to complement the analyses performed over the last four years over the reclaimed lands of the Shanghai city .
The availability of updated DEMs of the areas subject to sea-level rise (and/or flooding) is also of fundamental importance. It is worth emphasizing that nowadays, global coverage catalogues of DEMs imaging most of the Earth’s surface are available (such as the ones recovered through the Shuttle Radar Topography Mission in 2001) and also new SAR missions have recently been specifically deployed (such as the TanDEM-X mission ) for the generation of updated profiles of the terrain. During the first months of activities, a DEM of the coastal area of the Shanghai megacity has been generated by applying the method - based on the use of bistatic SAR data acquired by the TerraSAR-X and TanDEM-X sensors. The analysis of the generated DEM, as well as its use for the application of flooding models in the Shanghai area, is still in progress.
The preliminarily results of the activities performed during the first year of this D4 project will be analyzed and properly integrated with the results of other investigations, for instance by performing SAR Tomography  experimentations over Delta river cities.
 Berardino, P., G. Fornaro, R. Lanari, E. Sansosti (2002), A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms, IEEE Trans. Geosci. Remote Sens., 40(11), 2375-2383.
 A. Ferretti, C. Prati, and F. Rocca (2001), Permanent scatterers in SAR interferometry, IEEE Trans. Geosci. Remote Sens., 39(1), 8-20.
 Zhao Q., Pepe A., Gao W., Lu Z., Bonano M., He M.L., Wang J., Tang X. (2015) A DInSAR investigation of the ground settlement time evolution of ocean-reclaimed lands in Shanghai, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 8, 1763-1781.
 Krieger G., Moreira A., Fiedler H., Hajnsek I., Werner M., Younis M., Zink M. (2007) TanDEM-X: A satellite formation for high-resolution SAR interferometry. IEEE Tans. Geosci. Remote Sens., 45, 3317-3340.
 Kubanek J., Westerhaus M., Schenk A., Aisyah N., Brotopuspito K., Heck B. (2015a) Volumetric change quantification of the 2010 Merapi eruption using TanDEM-X InSAR. Remote Sensing of Environment, 164,16-25.
 Kubanek J., Richardson J., Charbonnier S., Connor L. (2015b) Lava flow mapping and volume calculations of the 2012-13 Tolbachik, Kamchatka fissure eruption using bistatic TanDEM-X InSAR. Bulletin of Volcanology, 77,1-13.
Evaluation of spatially-variable shallow-water frictional tides in the Hong Kong coastal regime
The Chinese University of Hong Kong, Hong Kong S.A.R. (China)
Mean sea-level (MSL) is rising worldwide, and correlated changes in the ocean tides are also occurring; the combination of both may increase or diminish total sea-levels (TSL) in a complex manner. Higher ambient water levels can increase the flood risk to coastal zones, more so under storm surge episodes. However, even without a storm event, increasing MSL coupled with increasing tides may lead to more nuisance flooding, or flooding events produced from the coupling of high tides and rising MSL. Hong Kong is particularly sensitive to changes in water levels, as it has a large population with much of its infrastructure near the shore. Furthermore, land subsidence and past reclamation projects may have induced changes in resonant and frictional properties of the tides, which may yield non-uniform spatial changes in water levels throughout Hong Kong. In this work, the historical full-spectrum tidal variability at a number of coastal tide gauges in Hong Kong is determined, and the past behavior of the relations between major tides and shallow-water overtides is examined to understand the changes in friction and resonance and the implication for future water level spectra in the region. Additionally, the locations surrounding each tide gauge is examined via remote sensing images from the Sentinel series of earth observing satellites, and past and present images are contrasted to determine changes to coastal morphology, and compared to the frictional determinations of the ground based gauges and to the history of land subsidence and land reclamation in the region.
Semi-empirical Estimation of Significant Wave Height using Sentinel-1A SAR
1Institute of Space and Earth Information System, The Chinese University of Hong Kong; 2School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China
In recent years, quantitative measurements of significant wave height (SWH) by the use synthetic aperture radar (SAR) and radar cross section (RCS) methods has been proven effective in different approaches without prior knowledge of wind information. An update of an existing simple semi-empirical algorithm, aided by parameterized filtering of RCS, is presented in this study to address the issue of how the RCS values depend on empirical algorithms in different systems, using the wavelength value of the dominant wave peak and the relationship function of RCS to incidence angle derived from the SAR image. To determine the wavelength of dominant wave peaks, we implement a contrast limited adaptive histogram equalization (CLAHE) method, based on a parameterized image texture analysis. An adaptive filtering method ensures a statistically robust determination of the filtering parameter, resulting in a higher contrast SAR image that allows more efficient dominant wave peak identification, as clearer wave patterns can be revealed by higher image contrast level. We also propose a preliminary empirical update for the backscatter cross-section to incidence angle function for vertical polarization in a 5.405 GHz SAR system. Standard meteorological buoy data from National Buoy Data Center (NDBC) is used in development of the empirical model through validation. This research employs Level-1 GRD Sentinel-1A SAR images from 2015 to early 2017 that look at Hawaii and the central part of the west coast of the United States of America, selected to represent deep to shallow water depth and river influenced estuaries. However, extreme sea states are not considered due to the limitation of the image repository and buoy data availability. Beside the two analysis methods described above, additional detailed analyses are conducted on the sea state relation to the velocity bunching mechanism, based on SWH estimation result.
|10:30am - 12:00pm||E3-ID32260: Surveillance of Vector-Borne Diseases|
|LAND & ENVIRONMENT|
Risk Evaluation, Surveillance and Forecast of Vector-Borne Tropical Diseases by Earth Observation Data Mining
1National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, China, People's Republic of; 2Academy of Opto-electronics, Chinese Academy of Sciences, China, People's Republic of; 3Hong Kong Baptist University, Hong Kong SAR
Among those diseases threatening human health and well-being, many epidemic and infectious diseases are closely related to natural environment due to the presence, breeding and evolution of their pathogens or reservoir hosts, especially vector-borne diseases (e.g. schistosomiasis, malaria and dengue, etc.) which rely heavily on their vectors. Therefore, monitoring the diseases' vector is an important way to prevent and control the vector-borne diseases.Because of complex spatial distribution and dispersion of typical diseases and their vectors, it is difficult to acquire relevant environmental factor data by traditional in-situ measurements. Remote sensing technology provides the capability of obtaining temporal-spatial variations of ground environmental factors. However, remote sensing experts may not exactly know what environmental factors are required to identify the incubators of vector-borne diseases. On the other hand, effective RS data processing and parameters retrieval techniques are also challenges for hygiene experts who are lack of experience of remote sensing applications. Taking into account of different type of massive data are involved, computing scientists with substantial intelligent data analysis expertise is crucial to successfully incorporate advance intelligent data analysis, such as data mining, pattern analysis. Consequently, any single of these disciplines is insufficient, it is essential to bring together scientists from computing science and remote sensing along with domain experts to foster a substantial collaboration.This proposed project aims to apply advanced remote sensing and computing technologies into monitoring and early warning of vector-borne diseases, e.g. schistosomiasis, malaria and dengue. First is to reveal environmental factors which have significant influences on the breeding of epidemic disease and its vectors. Then the project will make full use of the advantage of European and Chinese earth observation resources and the partners capability to develop parameter inversion, feature extraction and pattern analysis methods that will be used to characterise environmental features and habitants that are mostly suitable for the growth and dispersion of vector-borne disease and dynamic monitoring. Furthermore, temporal-spatial models of the distribution of vector-borne diseases will be developed by data mining techniques. Finally, the driving mechanism and data assimilation methods of land surface process model will be explored in order to implement identification and early warning of vector-borne disease transmission areas. All the institution of the project can provide sufficient funding to run the whole project successfully. The outcomes of the project will help to decrease the scope and extent of vector-borne diseases, and improve prevention & control capabilities to vector-borne diseases. Additionally, the research results can be used to assess environmental characteristics around the sits of major infrastructure and facilities, and provide the suggestion on site selection and implementation of infrastructures. The synthetic feature extraction techniques developed for multi-source multi-level remote sensing data can also be applied to other service fields, sustainably making contribution to knowledge within the communities.
Remote Sensing Monitoring of Vector-borne Parasitic Disease
1Academy of Opto-electronics,CAS, China; 2National Institute of Parasitic Disease, China CDC
Approximately half of the world’s population is at the risk of at least one vector-borne parasitic disease. The survival of intermediate hosts of vector-borne parasitic diseases is governed by various environmental factors, and remote sensing can be used to characterize and monitor environmental factors related to intermediate host breeding and reproduction, and become a powerful means to monitor the vector-borne parasitic diseases. In this research, satellite remotely sensed data has been used to obtain the environmental factors (vegetation, soil,temperature, terrain et al.), which are related to the living, multiplying and transmission of intermediate host. Then based on ground truth data, the remote sensing monitoring model of the intermediate host has been developed, which can enhance the remote sensing monitoring capabilities of the vector-borne parasitic disease and provide the theoretical foundation and technical support for diseases prevention and control.
|12:00pm - 2:00pm||Lunch|
|2:00pm - 3:30pm||A3-ID32296: LIDAR Studies and Validation|
|ATMOSPHERE - CLIMATE - CARBON|
Long-Range Dust Transport And Validation Using Ground-Based And Satellite Lidar Observations：Field Campaigns
1Ocean University of China (OUC), Qingdao, China; 2Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
The atmospheric particles have a remarkable impact on the global environment and climate change. The long-range transport of dust is an important part of the global biogeochemical cycles. It is significant and urgent to investigate dust on its optical properties, long-range transport, aging, and deposition. ESA decided to implement the Atmospheric Dynamics Mission ADM-Aeolus and the Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) to provide global profiles of wind, clouds, aerosols, and properties together with derived radiative fluxes and heating rates. ADM-Aeolus will carry the first wind lidar in space and launch is currently scheduled for the end of 2017. EarthCARE will carry cloud profiling radar, HSRL (High Spectral Resolution Lidar) and multispectral imager and is scheduled for launch in 2018. The research goals of TROPOS are investigations to aerosol type characterizations and the impact of aerosols on clouds and their properties. For this purpose, TROPOS developed several multiwavelengths and polarization Raman lidar systems (about 10 PollyXTs, MARTHA and BERTHA) and is using these systems at different continents. The recent and ongoing campaigns are the Central Asian Dust Experiment (CADEX), the Widefield Sky Scatterer Tomography by Lidar Anchor together with Technion Haifa, the Atlantic atmospheric observation experiment (OCEANET), and the Cyprus Clouds and Aerosol and precipitation experiment (CyCARE). Ground-based WACAL (WAter vapor, Cloud and Aerosol Lidar) was developed by the lidar group at OUC (Ocean University of China) and deployed during several field campaigns, including the third Tibetan Plateau Experiment of Atmospheric Sciences (TIPEX III) in Naqu (31.5°N, 92.05°E) with a mean elevation of more than 4500 m above MSL in summer of 2014. HSRL and CDL (Coherent Doppler Wind Lidar) developed by OUC were also deployed in several field campaigns in the coastal zone and China Seas. Lanzhou University (LZU) established a Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and conducted lidar observations of dust aerosol physical optical characteristics near the resource area in the northwest of China. In order to investigate the characterization of atmospheric bioaerosols along transported pathways of dust aerosols, a multi-channel lidar spectrometer system was developed to observe Mie, Raman scattering and laser-induced fluorescence excitation at 355 nm from the atmosphere. Long-range transport of Asian dust from the Taklimakan and Gobi deserts was studied based on CALIPSO lidar measurements. German Aerospace Center's (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Institute of Atmospheric Physicsa (IPA) is a member of ESA´s ADM-Aeolus Mission Advisory Group, Head of ESA funded pre-launch campaign study and contributor to algorithm and processor studies for Aeolus data products. DLR-IPA conducted several flights in the Mediterranean area which aimed at aerosol (incl. Saharan dust) detection using the ALADIN Airborne Demonstrator (A2D).
The first project objective is the comprehensive observations of vertical profiles of optical properties, flux and the deposition of dust during the long-range transport over continents of Europe and Asia. Based on the ground-based PollyXT, WACAL, CDL and HSRL, ADM-Aeolus and EarthCARE satellites, combining back trajectory model from NOAA, it is available to determine the dust source region, the main transport route and the main deposition areas. The second project objective is to validate the ADM-Aeolus and EarthCARE wind, cloud and aerosol data products. Ground-based co-located measurements with PollyXT, BERTHA, WACAL, CDL and HSRL lidars during overpasses of Aeolus and EarthCARE are foreseen in China (Costal cities, China Seas, inland cities, Tibetan Plateau, Taklimakan desert) and in Central Europe. An overview of the field campaigns will be presented in this report together with observation results from the ongoing data analysis.
Preparation of the Calibration – Validation phase with the Airborne Demonstrator for the ESA ADM – Aeolus Wind-Lidar Mission during the international campaign NAWDEX 2016
The spaceborne wind lidar ALADIN shall provide vertical wind profiles
Preparation of Cal/Val of Spaceborne Aerosol and Carbon dioxide Detection Lidar (ACDL) by Ground-based and Airborne sounding Instruments Observations
1Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences; 2Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences; 3Ocean University of China
The spaceborne Aerosol and Carbon dioxide Detection Lidar (ACDL) will measure the global column concentrations of carbon dioxide (CO2) and aerosols profiles. The column concentrations of carbon dioxide are measured by integrated path differential absorption (IPDA) lidar technique. The aerosols and clouds profiles are obtained by high resolution spectrum lidar (HRSL) technique. Both techniques are combined in the ACDL lidar payload. The dedicated atmosphere and environment monitoring satellite will carry the ACDL lidar and is scheduled to launch in about 2020. The spaceborne engineering prototype of the lidar with 1m SiC telescope was developed in 2016. And the single frequency and three wavelength laser with high pulse energy was developed and the environmental vibration testing was carried out. A ground-based double-pulse 1572 nm IPDA lidar is developed for carbon dioxide concentrations measurements. The lidar measured carbon dioxide concentrations continuously by receiving the scattered echo signals from a building about 1300 m away. On the same time the other two instruments of TDLAS (Tunable Diode Laser Absorption Spectroscopy) and in-situ carbon dioxide analyzer measured the carbon dioxide concentrations. The carbon dioxide concentrations bias between IPDA lidar and TDLAS measurement was validated to be less than 2 ppm. An airborne lidar prototype with high altitude platform is being developed to verify the retrieval algorithms of spaceborne ACDL lidar. The lidar will also be implemented to validate the Chinese passive CO2 measurement satellite TanSat in future.
|2:00pm - 3:30pm||B3-ID32405: Coastal Dynamics from X-temp Data|
|OCEANS & COASTAL ZONES|
China’s geostationary optical satellite GF-4: initial evaluation, processing and ocean application
1the first institute of oceangraphy, FOA, China; 2Plymouth Marine Laboratory, United Kingdom; 3Finnish Environment Institute SYKE, Finland
China successfully launched the geostationary orbiting optical satellite GF-4 on December 29th, 2015. The satellite can image the specific location of interest many times during the daytime with 50m (400m) spatial resolution in the visible (infrared) bands. Based on the GF-4 data, the following researches were performed. (1) The signal-to-noise ratio and georeference accuracy of GF-4 images was evaluated. (2) The vicarious radiometric calibration of GF-4 was performed with the concurrent GOCI data, and the atmospheric correction of GF-4 was further carried out. (3) The diurnal variability of the drifting velocity of the floating macro-algal bloom (green tide) in the Yellow Sea was analyzed with the GF-4 images.
Collaborative Monitoring Green Tide By MODIS And Landsat TM/ETM+ Images
1Qingdao University, Shandong People's Republic of China,; 2National Marine Environmental Monitoring Center,Dalian, China
Every satellite has its own revisited period, so it is impossible to monitor a whole process of green tide bloom using only one kind of data source acquired from one satellite. The requirement of monitoring green macroalgae collaboratively by multi satellites instruments has been put on the table. In order to make green macroalgae monitoring by MODIS (250-m resolution) and Landsat TM/ETM+ (30-m resolution) images possible, the detection results in the same region and the same time from the two data sources are compared, and the relationship between them is analyzed. It is found that the detection result from MODIS image is over 5 times of the one from Landsat TM/ETM+ image. According to this statistic relationship, a transformation-detection method of green macroalgae from 250m resolution MODIS image to 30m resolution results is presented. The experimental results show that the proposed approach can provide an effective method to monitor green macroalgae collaboratively by MODIS and Landsat TM/ETM+ images.
Sentinel-3A OLCI: initial evaluation and ocean application
1the first institute of oceangraphy, FOA, China, People's Republic of; 2Plymouth Marine Laboratory, United Kingdom; 3Finnish Environment Institute SYKE, Finland
On February 16th, 2016, ESA successfully launched the Sentinel-3A satellite. Among the four Earth-observing instruments, the OLCI (Ocean and Land Colour Instrument) is designed to continue the ENVISAT MERIS capability of ocean color monitoring.
Based on the OLCI L1 data, the following researches were performed. (1) The TOA reflectance, signal-to-noise ratio and georeference accuracy of OLCI images were evaluated and compared with those of MODIS and VIIRS. (2) The floating macro-algal bloom (green tide) in the Yellow Sea was detected using the OLCI images.
|2:00pm - 3:30pm||C3-ID32388: TPE Cryosphere and River Dynamics|
|HYDROLOGY & CRYOSPHERE|
A Decreasing Glacier Mass Balance Gradient From The Edge Of The Upper Tarim Basin To The Karakoram East During 2000-2013
1The Chinese University of Hong Kong, Hong Kong S.A.R. (China); 2Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China; 3Institute of Tibetan Plateau Research, The Chinese Academy of Sciences, Beijing, China; 4COMET, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
In contrast to the glacier mass losses observed at other locations around the world, some glaciers in the High Mountains of Asia appear to have gained mass in recent decades, which was called as ‘Karakoram anomaly’ or ‘Karakoram-Pamir anomaly’. Recent study to laser altimetry data found the centre of the anomaly might locates at the West Kunlun instead of the Karakoram. We performed differential interferometry to 14 pairs of bistatic TerraSAR-X and TanDEM-X observed the West Kunlun and its surroundings obtained at ~2013 by referring to SRTM observed in 2000. After removing seasonal effect and penetration depth differences, it found during 2000 and 2013, glacier mass balance rate at the West Kunlun was 0.128 ± 0.055 m w.e.a-1 and most of its surrounding area also experienced a mass gain that varied from 0.043 to 0.363 m w.e.a-1, with a decreasing gradient from northeast to southwest. At southwest of this study region, glacier presented significant mass lost at -0.286 ± 0.067 m w.e.a-1. For the West Kunlun region, northern slope gained mass quicker than southern slope, eastern and western part gained mass quicker than central part. Comparing to previous studies applied ICESat satellite laser altimetry data, similar results of glacier height changing was obtained at their footprints. Our results suggested a decreasing gradient of glacier mass balance from the Upper Tarim edge to the Karakoram, which is similar to previous ICESat derived gradient rather than topographic difference results derived with SPOT/HRS and SRTM. Glacier surging was common at the West Kunlun. Surging and quiescent glaciers identified by glacier height changing pattern was almost the same to previous study derived with feature tracking. They cover almost one third of the total glacierized region. For the West Kunlun, glacier height changes in different elevation bins for non-surging glaciers present significant and homogeneous height increasing above 5450 m, while below 5400 glaciers shows significant thinning, which indicate the warming and moisturizing trend in the centre of the anomaly area.
Glacier Surface Motion Monitoring in High Mountain Asia using Sentinel Observation
1The Chinese University of Hong Kong, Hong Kong S.A.R. (China); 2Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
Glacier is one of the most important climate change indicators in both regional and global scale. High Mountain Asia has the largest extend of glacier outside the polar region. As the Asian Water Tower, glacier in this region also has distinct ecological significance due to its vast water source. Its movement has close correlation with the risk of glacier lake outburst in highland. As a consequence, glacier dynamics in High Mountain Asia including mass balance, surface velocity and outline detection have been research hotspot. In recent years, synthetic aperture radar (SAR) observation has been regarded as an effective tool for glacier surface motion monitoring with wide range and high resolution. Therefore, it is essential to employ SAR observation to evaluate the velocity of glaciers in Tibet, China, which may be the basis for glacier dynamics and even climate change conditions in High Mountain Asia region.
SAR echo records both amplitude and phase information. From one aspect, the phase-based traditional differential SAR interferometry (D-InSAR) can achieve a millimeter accuracy in deformation detection theoretically while its application to glacier dynamics is generally limited by decorrelation. From another aspect, the intensity-based pixel offset tracking (POT), taking advantages of the intensity from backscatter signals, can implement large displacement in both range and azimuth direction whereas redundancy and error estimation in matching decorrelated patches arises in the calculation procedure. Hence an integrated method combining these two complements is applied to sub-region in High Mountain Asia in exploring glacier dynamics which can improve utilization of SAR observation.
In this study, acquisitions from Sentinel-1A and Sentinel-1B constitutes the data stack with a 6-day temporal baseline. Qualitative and quantitative evaluations of the glacier velocity are made for understanding the surface motion and glacier dynamics. Compared with other space-borne SAR acquisitions, the C-band Sentinel-1 data have smaller temporal decorrelation effects with shorter revisit time, which might be attributed to the good interferometry analysis.
|2:00pm - 3:30pm||D3-ID32365: Landslides Monitoring|
|SOLID EARTH & DISASTER RISK REDUCTION|
Research on Potential Landslide detection method using SBAS Technology——A Case Study of Minjiang River Basin
Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University
The synthetic aperture radar (SAR) interferometry (In-SAR) technique has already shown its importance in landslide mapping and monitoring applications. However, the usefulness of traditional differential In-SAR applications is limited by disturbing factors such as temporal decorrelation and atmospheric disturbances. And the Persistent Scatters Interferometry (PSI) technique need plenty of scenes, at least 25 scenes. Small Baseline Subsets (SBAS) is recently developed In-SAR approach. And it has a wide range of application prospects in the surface deformation monitoring because it could attain tiny deformation information of the surface and obtain long time series, slow deformation field of the surface. In this paper, we choose the Minjiang river basin as a study area, using SBAS approach obtained the surface deformation, and the deformation points which are unreasonable is removed according to certain conditions. The results show that the surface deformation points are mainly distributed on the right bank of the river, which is related to the low sensitivity of the ENVISAT data whose orbit is descending direction. Analyzed spatial relationship the potential landslide areas extracted using the spatial analysis method in ArcGIS software and the historical landslides. Meanwhile, the potential landslide areas are mainly distributed along the river. The main reason for this rule is the influence of the river erosion on the slope foot so that landslides distributed along the River; What’s more, among 30 historical landslides, 16 points lie in the deformation area, and 11 points lie in the potential landslide area, only 3 points are outside of the deformation area. Which shows that the landslide deformation points can better reflect the spatial distribution of historical landslides. Therefore, in the absence of historical landslide inventories, potential landslides detection by using deformation points provides effective assistance for regional disaster prevention and investigation.
Key words: landslide, SBAS technology, landslide deformation point, Minjiang River Basin.
Fusion of Multi-stack PS Point Clouds over Open Pit Mines
Northeastern University, China, People's Republic of
The surface deformation caused by mining is seriously threatening the safety of Mining area. It is necessary to continuously monitor the surface deformation of mining areas, in order to ensure the safety of production, as well as supporting early warning and risk control. Limited by the side-looking geometry of SAR sensors, only deformation along line-of-sight can be retrieved with time series InSAR technology from a single stack of SAR images. Since the terrain varies greatly in mining areas, it is very difficult to monitor the overall 3D deformation of mining pits and dump sites with a single stack of SAR images. Therefore, fusion of PS point clouds from multi-stack SAR images is necessary.
In this paper, fusion of PS point clouds retrieved by time series InSAR from multi-stack SAR images would be carried out. For the first step, the best PS points are select from the geocoded PS points with a threshold on the variance of estimated heights within a certain window. Then, binary images are generated with the selected PS points. Coarse offsets of the same object between binary images from different stacks are estimated and compensated. After that, point correspondences are created with the compensated PS points, followed by the least squares adjustment to calculate precise offsets between corresponding points. In the final step, offset compensation would be carried out, leading to precisely fused point clouds. the offset between PS points This fusion approach includes several key steps, such as selection of excellent PS points, finding the best PS point matching model between different stacks with iteration, least-squares adjustment without any reference data, PS point cloud re-locating with least squares adjustment, etc.
With this fusion method, three dimensional deformation of an open pit mine in Anshan will be estimated from multi-stack SAR images and presented in the fullpaper. 3D deformation of open pit mines is beneficial to monitoring the mining process. The relationship between mining activity and surface damage can also be analyzed with the assistance of surface deformation pattern, subsidence rate and other possible factors in the mining area.
Key words: Time Series InSAR; Surface Deformation; Multi-stack Fusion; Open Pit Mine
|2:00pm - 3:30pm||E3-ID32275: Agricultural Monitoring|
|LAND & ENVIRONMENT|
Sentinel-2 and UAVs multispectral imagery for site-specific crop and weeds detection
1CNR IMAA, Italy; 2University of Tuscia, Viterbo, Italy; 3NERCITA, Beijing, P.R. China
Accurate and recursive maps of crop and weeds at the field-scale could be of great interest with major economic and environmental impacts, including competition with native plant species, choking irrigation infrastructure, reducing agricultural yields and affecting the health of livestock.
The development of new generation multispectral satellite sensors and hyperspectral UAVs sensors has resulted in significant interest in their use for crop and weeds classification applications in view of their high spatial/spectral resolution. Small UAVs are more suited to site-specific weed management applications, as they can collect data at high spatial resolutions, which is essential for the classification of small or localized weed outbreaks. The extraction of features (spatial and/or spectral) that discriminate between the weeds of interest and background objects (i.e. different soils and crops) is crucial to map and monitor weeds in agricultural fields. Weed classification is an essential requirement for site-specific weed management in the context of precision agriculture, allowing a considerable reduction of herbicide spraying, with favorable environmental consequences. However, the spectral discrimination between crop and weeds from multi and hyperspectral remote sensing has yet to solve several issues, which is mainly due to the small spectral differences between crops of different species with also the requirement of a very high spatial resolution. Soil background effects are another problem that complicates weed detection in post-emergence row crops. Currently, no established methodology has been widely accepted, but different authors have employed successfully multivariate and machine learning algorithms such as PLSR-DA (Partial Least Squares Discriminant Analysis) and Support Vector Machine with a Radial Basis Function Kernel (Gaussian SVM) to discriminate and classify weeds from crops (Hermann et al., 2013; Hadoux et al., 2014) in using imaging spectroscopy field-based studies.
In the WP1 of the Topic 1, the main research activities are focused on: (a) setting up a spectral library of the most common crops and weeds in the investigated agricultural fields; (b) testing the capability of images acquired from both Sentinel 2 and UAVs imagery using different classification tools for crop mapping and weed detection; (c) mapping crops and weed patches in operational situations of site-specific crop management.
Improved classification methods are applied to Sentinel-2 and UAVs imagery for crop and weed detection: Minimum Distance (MD), Support Vector Machine (SVM), Neural Network (KNN), Random Forest (RF) and Spectral Feature Fitting (SFF).
Performance of the applied crop and weeds classification methods are compared on Sentinel-2 and UAVs’ data sets related to agricultural fields in Central Italy. Classification performances that can be obtained depends not only on the scenario and, thus, data set, but also on the specific sensor and platform as well as on the classification methods employed.
Moreover, with global revisit times of five days from next months onwards, Sentinel-2 based classifications can probably be further improved by using (a) temporal information in addition to the spectral signatures and (b) textural as well as canopy height information from Sentinel-1 radar images.
Herrmann, I., Shapira, U., Kinast, S., Karnieli, A., Bonfil, D.J. (2013). Ground-level hyperspectral imagery for detecting weeds in wheat fields. Precision Agriculture, 14, 637-659.
Hadoux X., Gorretta N., Roger J.-M., Bendoula R., Rabatel G. (2014). Comparison of the efficacy of spectral pre-treatments for wheat and weed discrimination in outdoor conditions. Computers and Electronics in Agriculture, 108 , 242-249.
High-throughput Field-based Phenotyping in Breeding with UAV Platforms
1Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, China; 2National Engineering Research Center for Information Technology in Agriculture (NERCITA), China
As field measurement of massive germplasm for complex traits in breeding is challenging, there's a strong demand for real-time, fast and nondestructive phenotyping to accelerate the breeding efficiency. Unmanned aerial platforms‑based remote sensing can be used to rapidly and cost‑effectively phenotype large numbers of plots and field trials. Strategies for high-throughput field-based phenotyping in breeding was investigated by National Engineering Research Center for Information Technology in Agriculture (coordinated by NERCITA) in recent years, where proximal remote sensing is the deployment of sensors using aerial platforms. Strategies include the following: 1) Selection and specification of UAV platforms for application of phenotyping in breeding; 2) Rapid processing of multi-source remote sensing data for high-throughput phenotyping; 3) Analysis of phenotypic information for soybean, maize and wheat in breeding (over 10,000 plots) by proximal remote sensing under different growth periods; 4) Determining the optimal growth stage, indexes and algorithm model for crop yield prediction; 5) Validation of the phenotypic information resolution and yield prediction using agricultural UAV for breeding plots to ascertain its stability and accuracy; 6) Genome-wide association study of morphological indicators and genotype of maize and the identification of candidate gene.
Exploitation of Multitemporal and Multisensor Earth Observation Data for Arable Crop Classification and Yield Assessment at the Farm Scale
1DAFNE, University of Tuscia, Italy; 2EOSIAL, University of Roma 'La Sapienza', Italy; 3CNR-IMAA, Rome, Italy; 4NERCITA, Beijing, China; 5RADI, CAS, Beijing, China
Many studies have demonstrated the advantage of the exploitation of multi-temporal and multi-sensor remote sensing data for the improvement of crop classification methods. However the methods based on optical and SAR data for monitoring arable crops, such as cereals and forage crops (e.g. wheat, barley, oats, triticale, ryegrass...), both at the local and regional level, are still far from being effective and operational. This is because usually small differences in the canopy reflectance and SAR backscatter occurs among these crops, hampering a clear and robust discrimination. There is however, an increasing requirement, e.g. in the context of the European agricultural policy of "coupled subsidy" (payment related to real crop cultivation on parcel), to identify individual crops. For example in the "crop diversification" measure, imposed by the “Greening Policy”, it is necessary to separate barley and wheat on the same farm, which is rather difficult when using only a type of data. The objective of WP1 of the topic 1 of the Dragon4 project ID. 32275 "Combined Exploitation Of Sino EU Earth Observation Data for Supporting The Monitoring and Management of Agricultural Resources", is the development of classification algorithms based on multitemporal optical and radar data allowing the incorporation of cropping systems dynamics information. In this context, a study was carried out in the Maccarese farmland test site (Central Italy), in which a quite extensive dataset, including both optical (RapidEye, Landsat8 and Zy-Yuan 3) and radar (Cosmo SkyMed and Sentinel-1) data, was collected during the 2015 crop growth season. These data were used to test a multi-temporal phenology-based classification algorithm, based on pixel-level decision tree (DT) incorporating information on temporal crop dynamics. The results were validated using the ground data available within a farm management geographic information system (GIS).
The same dataset was also employed for field-based wheat yield estimation, which is the objective of WP5 of topic 1 of the mentioned Dragon4 project. For this purpose, the remote sensing data were converted into biophysical variables (LAI and above ground biomass), using empirical relationships with ground data obtained during the 2015 crop season, in field campaigns carried close to the satellite acquisitions (on wheat, barley, alfalfa, broad bean and maize). For optical data, an algorithm based on the training of artificial neural networks with PROSPECT+SAIL model simulations was employed to retrieve biophysical canopy variables. These variables were then assimilated into the SAFY model (Duchemin et al., 2008, Environ Model Softw. 23, 876-892), using the Ensemble Kalman Filter (EnKF) method, to estimate grain yield. The models were re-calibrated on the basis of a preliminary sensitivity analysis study. Two versions of the SAFY model were compared, i.e. the original SAFY and a modified version (SAFYE) which includes a description of the soil water balance and water stress factors (Veloso, 2014, PhD Thesis, University of Toulouse, France). The results were validated using yield map data collected using a yield monitor system available on the farm's combine harvester machine. A very small difference emerged between the results of the two model versions, suggesting that the original SAFY version, which includes less parameters and input variables than SAFYE, is a suitable and practical choice for farm-based grain yield estimation, although water stress is inferred indirectly, from the processes regulating leaf growth.
Detection and Classification of Infestation Diseases by using multi- and hyper-spectral data
1Institute of Remote Sensing and Digital Earth, Chinese Academy of Science, China, People's Republic of; 2University of Chinese Academy of Sciences，Beijing, China; 3School of Aerospace Engineering, Sapienza University of Rome, Rome, Italy; 4Institute of Methodologies for Environmental Analysis, National Research Council of Italy, Rome, Italy
Yellow rust is one of the most important fungal diseases of wheat and have caused serious yield loss of winter wheat in China. Studies focused on detecting and monitoring of rust infestation highly rely on field investigation and visual judgement with an advanced pathogen attack. Automatic methods based on remotely sensed techniques and spectral absorption features for an early detection of rust disease are rarely discussed. On the other side, in Italy, the Province of Lecce, located in the region (Apulia) where the 35% of the Italian olive oil is produced has been significantly affected by the Xylella fastidiosa disease which caused a rapid decline in olive plantations, the so-called olive quick decline syndrome (OQDS, in Italian: complesso del disseccamento rapido dell'olivo). By the beginning of 2015 it had infected up to a million trees in the Lecce Province. Then this paper has two main objectives:
- determine the most sensitive spectral vegetation indices (SVIs) for characterizing specific pathological lesions of winter wheat leaves infected with rust disease, and then to propose a hyperspectral analysis procedure for the early detection and identification of rust diseases before specific symptoms became visible. Based on in situ hyperspectral data measured in experiments of 2002 and 2003 with a total of 122 samples, 14 pro-existing SVIs that are related to foliar physiological and photochemistry variations were assessed at different pathogen stages. And then, in order to extract the subtle spectral features between the healthy and diseased winter wheat leaves, an enhanced feature space (EFS) were developed by the non-linear combination and transformation of the identified SVIs. Based on this feature space, early differentiation of healthy leaves and leaves infected with yellow rust could be achieved by a Support Vector Machine (SVM) classifier. Finally, for validation and extension, this approach was also successfully implemented on MODIS data for mapping the rust occurrence conditions in the regional level in the major winter wheat planting area.
- presenting the preliminary results of the analysis of a time series of Landsat images of the Province of Lecce (Italy) spanning a period of seven years on the way to analyze the possibility of using available satellite images (e.g. L8 and Sentinel-2) datasets to assess the evolution of diseases on permanent crops (olive groves, vineyards), for example, the spread of phytosanitary threats as the Xylella fastidiosa (olive groves) or fungal trunk diseases (vineyards) in Italy.
Keyword: Yellow rust; Spectral vegetation indices; Early detection; Support vector machine
Estimation of winter wheat canopy nitrogen density at different growth stages based on N-PROSAIL model
1National Engineering Research Center for Information Technology in Agriculture, China, People's Republic of; 2School of Civil Engineering and Geosciences, Newcastle University
Nitrogen (N) is an important indicator of the plant nutritional status and then affects the end of wheat production. Rapid real-time monitoring of wheat N status is crucial for precision N management during wheat growth. Traditional inversion methods by remote sensing are mostly based on its relationship with vegetation index or spectral band. Some models are not suitable as the change of time and location. N-PROSAIL model (Yang et al., 2016) was developed by replacing the absorption coefficient of chlorophyll in the original PROSAIL model (with an equivalent N absorption coefficient, and it gave us a physical method to estimate canopy nitrogen density (CND, g m-2). Therefore, the objective of this study was to estimate CND at different growth stages by inverting the N-PROSAIL model.
Field experiments were carried out in 2012-2013, 2013-2014 and 2015-2016 at the National Precision Agriculture Experimental Base of Xiaotangshan town, Changping district, Beijing, PR China. Data acquisition included canopy hyperspectral reflectance, leaf area index (LAI, m2 m-2), and leaf nitrogen density (LND, µg cm-2), which were measured at four wheat growth stages, jointing (Z.S. 31), heading (Z.S. 47), anthesis (Z.S. 65), and filling (Z.S. 75). First, parameters of N, Cm, Cw, LAD, hspot, psoil, and solar zenith angle in N-PROSAIL model (Jacquemoud et al., 2009) were calibrated at different growth stages. Second, LAI and LND were inversed by Shuffled Complex Evolution (SCE-UA) algorithm and the estimation accuracy was tried to improve by using the calibrated parameters set at various growth stages. Finally, CND was calculated by LAI multiplied LND.
The inversion results with and without considering calibrating parameters at different growth stages were compared (Fig. 1). Without considering calibrating parameters at different growth stages (unified parameters at all growth stages, Li et al., 2015), The R2 and RMSE values for LAI and LND were 0.67 and 0.74, and 0.30 and 58.49 μg cm-2, respectively. Relationship between the simulated and measured CND showed well (R2 = 0.66, RMSE = 2.45 g m-2). After considering calibrating parameter at different growth stages, the estimation accuracy of LAI was improved (R2 =0.75, RMSE = 0.73), and LND estimation showed a significant improvement (R2 = 0.59, RMSE = 17.43 μg cm-2). In the end, the CND estimation performed better than CND estimation with unified parameter set at all growth stages, with R2 and RMSE values of 0.75 and 1.32 g m-2, respectively. These results confirm the potential of using N-PROSAIL model for CND retrieval in winter wheat at different growth stages and under variables climatic conditions.
Wheat Powdery Mildew Forecasting Using Artificial Neural Network
1Chinese Academy of Science, China, People's Republic of; 2University of Chinese Academy of Sciences; 3Institute of Methodologies for Environmental Analysis; 4Department of Astronautics, Electrics and Energetic
Wheat powdery mildew is one of the serious crop diseases which affects the food safety of China. Integrating multi-source information (Earth Observation-EO, meteorological, etc.) to support decision making in the sustainable management of wheat powdery mildew in agriculture is demanded. In this study, the Landsat8 remote sensing image of May 22nd, 2014 was used to extract the land surface temperature (LST) and many vegetation indices including normalized difference vegetation index (NDVI), enhanced vegetation index(EVI), triangular vegetation index (TVI), wetness index and renormalized difference vegetation index (RDVI). Site daily meteorological data including temperature, humidity, rainfall, sunshine hour from April to May was used to get the parameters delineating the environment condition such as average temperature from April 22nd to May 22nd, average humidity from April 22nd to May 22nd, total sunshine hour from April 22nd to May 22nd and number of rainy days with more than 0.1 mm rainfall from April 22nd to May 22nd. Corresponding space meteorological features were got by combining remote sensing image and site daily meteorological data. In the field work, 148 field sites were collected in study area and the degree of wheat powdery mildew in these sites was recorded. An independent t-test analysis was used to test the difference between disease and healthy sites based on calibration data. Those vegetation indices and environmental factors that failed to show a statistical significant(p<0.001) were eliminated. Five variables including RDVI, temperature, humidity, average temperature from April 22nd to May 22nd and average humidity from April 22nd to May 22nd were identified as optimal explanatory variables for developing the powdery mildew forecasting model. The artificial neural network was trained using feedforward neural network learning algorithm in combination with simulated annealing technique to learn the relationship between selected factors and powdery mildew. The powdery mildew forecasting model based on artificial neural network (ANN) was established to predict powdery mildew occurrence of wheat in Gaocheng, Jinzhou and Zhaoxian County, Shijiazhuang City, Hebei Province. The results obtained from the ANN model were compared with prediction model developed using support vector machine(SVM) technique. The accuracy of models respectively based on validation samples were obtained to evaluate the difference of performance of the models. The result showed that the overall accuracy of the ANN model was 86.49%, which is higher than SVM model(78.38%). The result reveals that ANN model could be used to forecast the occurrence of wheat powdery mildew and compared with the traditional forecasting model based on support vector machine, ANN model has a better performance.
Strategies for yiled prediction by UAV remote sensing in soybean breeding
Beijing Academy of Agriculture and Forestry Science, China, People's Republic of
Crop yield is one of the most concerned complex traits in crop research, which is linked to CO2 fixation through the photosynthetic process and partitioning of photoassimilates to the harvested part of the plant. The traditional methods for measuring crop yield are the use of manual sampling or establishing the relationship between agronomic factors or climatic factors and crop yield using statistical analysis methods. Many observations and samplings in field experiments are required to determine the parameters of the yield prediction model, which is time-consuming, low efficiency, and incomplete spatial coverage. Unmanned aerial vehicle remote sensing platforms (UAV-RSPs) equipped with different sensors have recently become important means for fast and non-destructive access to complex traits and have the advantages of flexible and convenient operation, on-demand access to data and high spatial resolution, which provide a new way for studying phenomics and genomics. As improving the accuracy and adaptability of the yield estimation model is a prerequisite for the application of UAV remote sensingthe objective of the research is to build crop yield prediction models that combine crop physiology and remote sensing parameters to improve the accuracy of yield prediction by UAV-RSP.
Field experiment tested 98 breeding materials of soybean was conducted by NERCITA in 2015. Unmanned aerial platform equipped with digital camera, multi spectral camera and hyper-spectrometer was used for field-based high-throughput phenotyping of soybean in breeding plots. Ten vegetation indices (VIs) including NDVI, RVI, GNDVI, PVI, OSAVI, EVI, DVI and NDVI705 and plant height, combining algorithms including partial least-squares regression (PLS), multiple linear regression (MLR) and multiple stepwise regression (MSR) have been adopted for predicting yield of soybean in breeding plots. The results showed that MLR performed best, with R2, NRMSE and d values of 0.83, 6.61 and 0.95, respectively, while MSR had the lowest accuracy, with R2, NRMSE and d values of 0.72, 8.59 and 0.91, respectively.
The UAV-based field phenotyping platform can be as a preliminary method for screening cultivar in soybean breeding. The UAV platform equipped with multi-sensors was able to identify the differences of yields among the cultivars of soybean. Combing proximal sensing data and crop physiological traits can improve the accuracy of yield prediction in soybean breeding. The UAV-based proximal sensing platform provided novel insights in accelerating the breeding efficiency.
Estimation of winter wheat leaf area index (LAI) and above ground biomass (AGB) based on hyperspectral analysis: Mapping using UHD 185 and unmanned aerial vehicle (UAV)
1Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China; 2School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo,454000, China; 3Department of Agriculture, Forests, Nature and Energy (DAFNE), Universita’ della Tuscia, Viterbo 01100, Italy; 4National Engineering Research Center for Information Technology in Agriculture, Beijing 100097, China; 5Key Laboratory of Agri-informatics Ministry of Agriculture, Beijing 100097, China; 6Beijing Engineering Research Center of Agricultural Internet of Things, Beijing 100097, China
Leaf area index(LAI) and above ground biomass (AGB) are considered as two most important physiological parameters for crops, its correct estimation has been the focus in the crops growth monitoring and yield prediction. With the development of remote sensing technology and its application in agriculture, LAI and ABG estimation have been one of the main research areas of agricultural remote sensing. In recent years, unmanned aerial vehicle (UAV) technology has emerged as a new platform for remote sensing sensors, can provide remote sensing image in higher temporal resolution and spatial resolution. This study provides insight into the LAI and ABG estimation using an ASD Field Spec 3 spectrometer on the ground and applied to mapping using an UHD 185 hyperspectral sensor on board an UAV. The UAV was an 8-propellered UAV platform with 6 kg take-off weight, 50 meters flying height and 8m/s speed. The canopy spectral of winter wheat was measured by two methods, a DJI-S1000 UAV equipped with UHD 185 hyperspectral sensor fly 50m high, and a ASD Field Spec 3 spectrometer on the ground. By using 550nm, 680nm and 800nm spectral from ASD Field Spec 3 spectrometer, a linear model for LAI and ABG estimation was established. Results indicate that the R2 was 0.78 and 0.60, RMSE was 0.60m2/m2 and 1.46 t/ha, MAE was 0.48 m2/m2 and 1.19 t/ha, respectively. After the hyperspectral image fusion and mosaic processing, hyperspectral image of whole study area was obtained. We applied the models for LAI and ABG estimation on the hyperspectral image of whole study area, and completed the winter wheat LAI and ABG monitoring, with results of LAI and ABG as follows: R2 was 0.76 and 0.44, RMSE was 0.64 m2/m2 and 1.48 t/ha MAE was 0.54 m2/m2 and 1.15 t/ha. The results suggest the UAV UHD 185 hyperspectral system and the models have high application potential.
|3:30pm - 4:00pm||Coffee Break|
|4:00pm - 5:30pm||A3-ID32426: Calibration and Data Quality|
|ATMOSPHERE - CLIMATE - CARBON|
Calibration and Intercalibration of microwave radiometer time series: Status and plans for Dragon-4
1Space Science and Engineering Center, University of Wisconsin – Madison, US; 2Earth and Environmental Sciences, Vanderbilt University, Nashville, US; 3Informus GmbH, Berlin, Germany; 4CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese Academy of Sciences, Beijing, China
The Microwave Radiometer (MWR) flown on Envisat, ERS-1 and ERS-2 provides a nearly uninterrupted time series of microwave observations over a period almost 21 years between 1991 and 2012. This dataset is complementary to other microwave datasets. From 2011, the Atmospheric Correction Microwave Radiometer (ACMR) on HY-2 provides similar measurement.
Firstly, we report on our efforts towards a fully inter-calibrated and validated physical retrieval of TCWV and LWP for MWR. We will address issues related to satellite inter-calibration, homogeneity of the derived time series of brightness temperatures, observation-simulation biases, and provided first results of fully physical retrievals.
Secondly, an outlook on ongoing and planned activities within Dragon-4 will be given and the importance of the results in light of the upcoming Sentinel-3 mission and the HY-2 series will be discussed.
The Generation of Sensor Independent Radiometric Product for Field Calibration and its Application Demonstration
1Academy of Opto-Electronics, CAS, China, People's Republic of; 2Key Laboratory of Quantitative Remote Sensing Information Technology, Chinese Academy of Sciences, Beijing,China; 3Wave Interaction & Propagation Section (TEC-EEP), European Space Agency, Noordwijk, The Netherlands
Calibration and validation (Cal&Val) is one of the most important means for assuring satellite payload performance and data quality. It could guarantee the accuracy of the retrieved information, make the remote sensing data consistent and traceable, and maintain the sensor performance during the operational phase. The challenges in the Cal&Val include the lack of consistent remote sensing (RS) product assessment standards, the uncertainties introduced by atmospheric effect, as well as the gaps in non-synchronous measurements between satellite observation and in situ measurements. In this project, great achievement has been done in carrying out cooperative research on the high-frequency optical calibration with the aid of the Radiometric Calibration Network (RadCalNet) activities and permanent targets over Baotou site in China.
(1) Development of automated radiometric calibration system and its operations. On benefit of RadCalNet and the cooperation of the Cal&Val experts from European and Chinese intuitions in the DRAGON programme, the automated surface spectral reflectance measurement system has being developed and installed over four permanent targets with different reflectance in Baotou site, which can automatically and traceably acquire the target characteristics and atmospheric parameters. In consideration of the land surface variety and the adjacent effect, the TOA radiance is simulated with the input of a background reflectance driving the MODTRAN, and the Level 1 BOA reflectance product is generated according to the input files defined by RadCalNet data center.
(2) Automated radiometric calibration demonstration for Chinese and European satellites. The data portal for standard product service has been established under the leadership of ESA, and now is in operation. Since the late last year, ESA have organized test users to calibrate their satellites using the RadCalNet standard products over four demonstrated sites. Among them, the predicted TOA radiance over Baotou site is compared with the observations of Sentinel-2a, ZY-3, GF-1, etc. This is not only important to validate the calibration capability of Baotou site, but also would greatly benefit improving the calibration accuracy of optical sensors, and assuring the data consistency from different sensors.
(3) The uncertainty analysis on the standard radiometric calibration product. The calibration uncertainty over Baotou site include the following aspects: 1) Traceable accuracy and measurement repeatability of the automated measurement system, traced to the primary standard of NPL through the transfer calibrator; 2) Non-uniformity and BRDF effect of the ground standard targets; 3) Measurement errors of typical atmospheric parameters, which are given by AERONET since the sun-photometer Cimel CE-318 in Baotou site has been included in AERONET; 4）Adjacent effect, caused by the point spread function (PSF) of the imaging system and the multiple scattering among surface and atmosphere; 5) Uncertainty aroused by radiative transfer calculation of MODTRAN, which is simulated based on Monte-Carlo theory.
Validation of Satellite Products over Northern China by Ground-based MAX-DOAS and FTIR Instruments
1Institute of Atmospheric Physics, Chinese Academy of Sciences, China, People's Republic of; 2University of Chinese Academy of Sciences,Beijing, China; 3Belgium Institute for Space Aeronomy, Brussels, Belgium
A ground-based MAX-DOAS and a Bruker IFS 125HR have been deployed in Xianghe Station, Northern China, of the Institute of Atmospheric Physics, Chinese Academy of Sciences, and another Bruker IFS 125M has been installed in Xinglong Station. The MAX-DOAS has been running for more than ten years, providing a large number of high quality data of NO2, SO2, etc., for deriving their trends, and for validating the satellite products of OMI, GOME-2, and SCIMACHY. In Xianghe station, CIMEL sunphotometer, gas analyzers, automatic meteorological station, and a 100-meter tower can provide aerosol optical properties, air quality status, and meteorological conditions in the planet boundary layers. The two Bruker FTIR instruments in Xianghe and Xinglong stations aim at providing the greenhouse gas such as CO2, CH4, N2O, and for validation of GOSAT, OCO-2, and TanSat products in future. The FTIR in Xinglong station has been operating for more than one year, and some data has been obtained, which has been used for validation of GOSAT products.
Key words: MAX-DOAS, FTIR, NO2, CO2, Xianghe Station.
Research on Calibration, Validation and Retrievals on Satellite-based Microwave Instruments
National Space Science Center, Chinese Academy of Sciences, China, People's Republic of
Global monitoring of precipitation is important because of its significant human consequences. However, the multiplicity of hydrometeor types and their small- and large-scale spatial inhomogeneities make accurate measurements difficult. For example, rain gauge measurements are significantly impaired by wind, poor global coverage, and the non-uniformity of rain. Both ground-based radars and passive microwave satellite sensors sense precipitation aloft and are generally unable to discern how much of that precipitation evaporates before impact.
The paper develops a passive sub-millimeter precipitation retrievals algorithm for Microwave Humidity and Temperature Sounder (MWHTS) onboard the Chinese Feng Yun 3C (FY-3C) satellite. The retrieval algorithm employs a number of neural network estimators trained and evaluated using the validated global reference physical model NCEP/WRF/ARTS, and works for seawater. NCEP data per 6 hours are downloaded to run the Weather Research and Forecast model WRF, and derive the typical precipitation data from the whole world. The Atmospheric Radiative Transfer Simulator ARTS is feasible for performing simulations of atmospheric radiative transfer. Rain detection algorithm has been used to generate level 2 products. Retrievals are reliable for surface precipitation rate higher than 0.1 mm/h at 15km resolution, which is in good agreement with those retrieved using the Precipitation retrieval algorithm version 1(ATMP-1) for Advanced Technology Microwave Sounder (ATMS) aboard Suomi NPP satellite.
Meanwhile, calibration and validation between similar instruments onboard different satellites are also important to ensure the validity of observations and accuracy of precipitation retrievals. In the ongoing work, we are going to carry out the calibration and validation among FY-3C MWHTS, FY-3B MWHS and ATMS.
Lab Evaluation of Nitrogen Dioxide Spectral Analysis of the Environmental trace gases Monitoring Instrument
1University of Science and Technology of China, China, People's Republic of; 2Max Planck Institute for Chemistry, Mainz, Germany; 3Meteorological Institute, Ludwig-Maximilians-Universität München, Germany
The Environmental trace gases Monitoring Instrument (EMI) onboard Chinese high-resolution remote sensing satellite GF-5 is an imaging differential optical absorption spectrometer, expected to be launched in September of 2017. The EMI instrument will measure earthshine radiances with the wavelength range from 240 to 710 nm at moderate spectral resolution (0.3-0.5nm) at nadir. The EMI is tasked with quantitatively measuring global distribution of tropospheric and stratospheric trace gases such as NO2, O3, and SO2. The prelaunch calibration phase is essential to acquire necessary knowledge on the properties and performance of the EMI instrument as well as support data processing and retrieval. This work focus on nitrogen dioxide retrieval from on-ground measurements of gas cell and atmospheric scattering light, and an evaluation of the performance of the EMI instrument from the retrieval.
|4:00pm - 5:30pm||B3-ID32235: Extreme Weather Monitoring|
|OCEANS & COASTAL ZONES|
Microwave Satellite Measurements For Coastal Area and Extreme Weather Monitoring
1Università di Napoli Parthenope, Italy; 2Shanghai Ocean University, China; 3Open University, Milton Keynes, UK; 4Zhejiang Ocean University, China; 5Institut de Ciencies del Mar, Barcelona, Spain; 6Chinese Academy of Sciences (CAS)
The project aims at exploiting microwave satellite measurements to generate innovative added-value products to observe coastal areas also under extreme weather conditions. The following added-values products are addressed: coastal water pollution, coast erosion, ship and metallic target detection, typhoon monitoring.
To better state the goals, the project is framed into three subtopics: 1) SARCO - SAR-based Coast Observation; 2) Ship and Coastal Water Pollution Observation with Polarimetric SAR Architectures (SCoPeSAR); 3) SHENLONG: Sea-surface High-wind ExperimeNts with Long-range (satellite) Observations using Numerical Geophysical methods.
To reach the above-mentioned goals, single-polarization and polarimetric models will be analyzed and/or developed to generate added-value products that consist of risk/vulnerability maps, targets at sea maps and pollutants maps, cyclone/typhoon monitoring. Typhoon monitoring will be addressed using a multi-sensor approach based on the exploitation of SAR, scatterometer and radiometer measurements. Hence, models to deal with extreme wind conditions will be analyzed/developed.
Analysis of the SAR-derived Wind Signature over Extra-tropical Storm Conditions
1Institute of Marine Sciences (ICM-CSIC), Spain; 2University of Naples Parthenope, Italy; 3Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China; 4National Oceanic and Atmospheric Administration (NOAA-NESDIS), USA; 5Royal Netherlands Meteorological Institute (KNMI), The Netherlands; 6Institut Français de Recherche pour l'Exploitation de la Mer (Ifremer), France
The monitoring and forecasting of tropical and extra-tropical storm tracks and intensities are strategic for the protection of coastal infrastructures and residents. The Synthetic Aperture Radar (SAR) can potentially be very useful for such purposes. In fact, its high spatial resolution and its capability to observe the sea surface in all weather conditions and at all times (regardless of the day or night-time) makes it one of the best candidate instrument for these goals.
Several empirical forward models or geophysical model functions (GMFs), which relate the normalized radar backscatter cross section to the sea surface wind vector, have been developed and successfully used for a wide variety of scatterometer and SAR systems at different frequencies and polarizations. The GMFs have high accuracy under no-rain and low-to-moderate conditions, although for C-band radar systems good-quality winds are also derived under rainy conditions. For high wind speed measurements, the accuracy rapidly decreases due to saturation of the co-polarized backscattered intensity and the reduction of friction between the sea surface and the wind. An improved high-wind GMF for C-band and SAR spatial scales (most GMF developments are based on scatterometer data) as well as new high-wind GMFs for other frequencies (e.g., X-band) are required for the successful wind retrievals under tropical and extratropical cyclone conditions.
In this study, the radar backscatter sensitivity to high winds (as given by the different GMFs) is revisited for both C-band and X-band systems, as well as for co-polarized and cross-polarized beams, using the NOAA P-3 flight winter campaign data from January-February 2017. During this campaign, the NOAA P-3 plane, equipped with several sea-surface wind sensing systems, i.e., the Step Frequency Microwave Radiometer (SFMR), the Imaging Wind and Rain Profiler (IWRAP), and dropsondes, underflew both Sentinel-1 (S-1) and Cosmo-SkyMed (CSK) satellite passes under storm conditions in the North Atlantic region. These extra-tropical storms are characterized by vast areas of nearly uniform very high-wind conditions, up to 30-35 m/s. The sensitivity analysis will therefore provide a comprehensive view of the main sensitivities of the radar backscatter (e.g., co-polarized, cross-polarized, polarization difference, polarization ratio) to relatively high winds, for a variety of incidence angles.
Moreover, two wind retrieval approaches commonly used by the SAR community, i.e., the azimuth cut-off method and the combined radar backscatter and doppler centroid scheme, will be used to derive the sea surface wind field for the mentioned SAR scenes and validated against the mentioned NOAA wind data sources as well as collocated scatterometer and Soil Moisture Active Passive (SMAP) derived winds.
Polarimetric backscattering of offshore platforms using dual-polarization TerraSAR-X data
1The Open University, United Kingdom; 2German Aerospace Center, Germany; 3Università degli Studi di Napoli Parthenope, Italy; 4Shanghai Ocean University, China; 5Shanghai Jiao Tong University, China
The amount of offshore platform is increasing significantly due to the improvements in drilling technology . In particular, the advances due to deep water drilling technology allows installation to be mobile (to not have a stable location) and to be in regions far from coastal water.
Offshore platforms pose a risk to environment with the threat of oil and gas spillage, especially due to their exposition to extreme weather conditions. Besides being a risk to the environment, since their location is not mapped on maps, they are also obstacles for yachts, low flying airplanes and merchant ships in low visibility conditions.
Offshore platforms are generally large metallic constructions, which should make them easily detected and mapped by using satellite Synthetic Aperture Radar (SAR) medium resolution imagery . However, we recently obtained analysed measurements  showing that some of the platforms in some acquisition geometries may be invisible in single-polarization backscattering images, leading to miss-detection. On the other hand the detection is still feasible if the dual polarimetric information is used.
In this work we exploiting a time series of dual-polarization TerraSAR-X data acquisitions over a cluster of offshore platform in the Gulf of Mexico. Among others, factors affecting the backscattering include polarization, resolution and incidence angle. Finally in this paper we also address how incoherent and coherent polarimetric observables can be exploited to detect platforms when the single polarimetric acquisition may fail detection.
 “International Energy Agency.” [Online]. Available: http://www.iea.org/.
 S. Casadio, O. Arino, and A. Minchella, “Use of ATSR and SAR measurements for the monitoring and characterisation of night-time gas flaring from off-shore platforms: The North Sea test case, “ Remote Sens. Environ., vol. 123, pp. 175–186, Aug. 2012.
 A. Marino, D. Velotto and F. Nunziate, “Offshore metallic platforms observation using dual-polarimetric TS-X/TD-X satellite imagery: a case study in the Gulf of Mexico,” IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens., under review, 2016.
Assimilation of Sentinel-1 SAR Winds in the Forecasting of Typhoon Lionrock
1Institute of Remote Sensing and Digital Earth, China, People's Republic of; 2National University of Defense Technology, China; 3Institut de Ciencies del Mar, Spain
The C-band synthetic aperture radar on-board ESA’s Sentinel satellites have the capability to provide high resolution wind vector information over the ocean surface. These wind vector data derived from SAR observations are available to the data assimilation system with real-time information of high accuracy. In this study, several comparison experiments are designed to investigate the impact of Sentinel-1 SAR winds data in the three-dimensional variational assimilation system for the Weather Research and Forecast model (WRF 3DVAR). The powerful Typhoon Lionrock is selected for this case study. Typhoon Lionrock struck and caused significant flooding and casualties in Japan and Russia in late August 2016. Its route changed several times and there are also several rapid intensification processes during its lifetime, which made its track very difficult to predict. Totally, 10 SAR images from 3 overpasses from August 27 to 29, 2016 are used in this study. The preliminary results demonstrate that SAR wind data can complement the scarce observations over the sea surface and improve the prediction of wind and pressure fields of Typhoon Lionrock. More detailed experimental results and analyses will be provided in the Dragon-4 symposium.
Polarimetric SAR Application For Coastal Water Pollution Monitoring
1Università di Napoli Parthenope, Italy; 2Shanghai Ocean University, China; 3The Open University, UK; 4NOAA/NESDIS, USA
Coastal regions are rapidly growing with increase in urbanization and population density. This results in increasing threats for terrestrial habitats and marine ecosystems. Hence, ever growing attention must be paid to the pollution of the coastal waters fed from urban watersheds and human-related activities discharges. Pollutants include pesticided, fertilizers, hydrocarbons, trace of heavy metals, organic compounds, pathogens and other anthropogenic debris. They alter the physical and biogeochemical state of coastal waters affecting marine life negatively.
Stormwater and wastewater runoff are the main sources of pollution in coastal areas that result from untreated runoff and pollutants coming from urban watersheds entering the coastal waters after rainstorms, through river discharges or during publicly owned treatment works. They impact coastal water quality severely through an increase in bacterial contamination due to the significant load of particles and dissolved compounds discharged during and immediately after storm events.
The environmental observation of stormwater runoff in near-shore waters is commonly undertaken through sparse sampling onboard coastal research ships. Nonetheless, the information those field measuremets provide is sporadic, expensive and coarse. The space/time gap left by in-situ monitoring can be filled in by satellite measurements.
Satellite synthetic aperture radar (SAR)-based and ocean color imagery from Aqua MODIS have been used to analyze the different compounds of runoff plumes, surfactants and sediment discharge. Nevertheless, optical observations are limited by rainy events, cloud cover and solar illumination. In particular, polarimetric SAR (polSAR) represents the most suitable tool for monitoring the pollution of coastal waters due to the all-day and almost all-weather detailed information it provides on the scattering mechanisms of the observed scene routinely, with wide area coverage, dense revisit time and fine spatial resolution. The capability of polSARs to detect marine oil spills, to identify natural oil seepages and to roughly characterize the damping properties of surfactants was widely proved.
In this study, the sensitivity of polarimetric parameters derived from fully-polarimetric (FP) SAR measurements on the presence of surface pollutants in coastal waters is investigated. Preliminary results are obtained processing a set of FP SAR data collected at C-band from Radarsat-2 over the coastal area of Piana del Sele (Salerno, Italy). The test site was selected since it is one of the most industrialized areas of Southern Italy that is severely affected by coastal water pollution. Preliminary results show that polSAR data can be effectively used to retrive detailed information on the coastal water quality that may be useful for the sustainable development and managament of coastal areas, including marine ecosystems protection, aquacultures and fisheries safety, water resources management.
1) Holt, B, Trinh, R. and Gierach, M.M., 2017,
“Stormwater runoff plumes in the Southern California Bight: a comparison study with SAR and MODIS imagery”,
in print on Marine Pollution Bullettin.
2) DiGiacomo, P. M., Washburn, L., Holt, B. and Jones, B. H., 2004,
“Coastal pollution hazards in southern California observed by SAR imagery: stormwater plumes, wastewater plumes, and natural hydrocarbon seeps”,
Marine Pollution Bulletin, vol. 49, pp. 1013-1024.
3) Migliaccio, M., Nunziata, F., Kurata, N., Vella, K., Matt, S., Soloviev, A. and Perrie, W., 2013, “Marine bacteria monitoring via polarimetric SAR”,
ESA PolInSAR Proceedings, ESA-ESRIN, Frascati, Italy.
4) Svejkovsky, J. and Jones, B., 2001,
“Satellite imagery detects coastal stormwater and sewage runoff”,
Eos Transactions, vol. 82, no. 50, pp. 621, 624, 625, 630.
5) Migliaccio, M., Nunziata, F. and Buono, A., 2015,
“SAR polarimetry for sea oil slick observation”,
International Journal of Remote Sensing, vol. 36, no. 12, pp. 3243-3273.
A Multi-sensor Approach for Coastal Area Monitoring
1Istituto Nazionale di Geofisica e Vulcanologia (INGV), Italy; 22Università degli Studi di Napoli Parthenope, Dipartimento di Ingegneria, Italy; 3Shanghai Ocean University, Shanghai, China; 4Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, China; 5Ministero per lo Sviluppo Economico (MISE), Direzione Generale per la Sicurezza anche Ambientale delle Attività Minerarie ed Energetiche – Ufficio Nazionale Minerario per gli Idrocarburi e le Georisorse (DGS-UNMIG)
This study proposes a multi-sensor approach to promote an effective coastal area monitoring strategy over areas that include critical infrastructures, e.g. on-shore and off-shore oil/gas extraction platforms and groundwater reservoirs*. The monitoring strategy includes both land-side and sea-side observations using remotely sensed measurements.
With respect to the land-side, multi-temporal differential Interferometric Synthetic Aperture Radar (DInSAR) and Global Navigation Satellite System (GNSS) techniques are exploited to monitor subsidence phenomena along on-shore hydrocarbon and groundwater reservoirs, where surface deformations can be correlated to the extraction of resources from the subsoil.
With respect to the sea-side, effective SAR techniques are exploited to take benefit of multi-polarization SARs to observe oil/gas rigs/platforms and to observe oil discharges close to the oil extraction sites.
The proposed approach aims at testing and improving the standards of security for the exploitation of underground resources, as well as providing ad-hoc procedures to monitor interested areas.
*The present work is supported and funded both by Italian Economic Development Ministry (MISE) under the MISE-DGRME research project (ID 0752.010) and the DRAGON-4 Cooperation Proposal “SARCO - SAR-based Coast Observation” (ID 32235).
A ship detection method improving the polarimetric notch filter for dual-polarization Sentinel-1 images
1Shanghai Jiao Tong University, China, People's Republic of; 2Open University,Milton Keynes, U.K
Many countries are focusing on maritime surveillance due to the interests in maritime shipping and the environment. The fact that more than eighty percent of goods traded worldwide are transported by sea is an indicator of the large amount of maritime traffic . Not all the vessels uses the Automatic Identification System (AIS) , especially some smaller ships, and therefore they need to be monitored with independent systems. Therefore, using SAR data to detect ships has become more and more valuable.
Because of the complex structure of ships, their scattering mechanisms, which mainly consist of multiple reflections, are different from those of ocean surface . These differences can be easily detected by using some polarimetric features. Compared with single-polarization backscattering images, dual- or quad-polarization images can provide more information about the scattering mechanisms composing the ships. This will therefore increase the discrimination between ships and ocean also in the case of ships where the overall amplitude is comparable to the one of the sea.
In this paper, we start from the Geometric Perturbation Polarimetric Notch Filter (GP-PNF) and extend the detector feature vector with many more polarimetric features [4-5]. Then we perform a Principal Component Analysis (PCA) to reduce the size of the vector and use this in the represent the full dataset in a new basis and use this basis to perform the PNF.
In our work, we choose some dual-polarization Sentinel-1 data as the experimental datasets. Experimental results show the effectiveness of the new method, especially in extreme weather conditions.
Gao, “Preliminary observations on efforts to target security inspection of cargo containers,”
USA Office Report, Dec. 2003.
P. A. Lessing, L. J. Bernard, and C. B. J. Tetreault et al., “Use of the Automatic Identification
System (AIS) on autonomous buoys for maritime domain awareness applications,” Oceans, pp.18-
21, Feb. 2007.
D. Velotto, M. Scoccorsi, and S. Lehner, “Azimuth ambiguities removal for ship detection using full polarimetric X-band SAR Data,” IEEE Trans. Geosci. Remote Sens., vol. 52, no. 1, pp. 76-88, Jan. 2014.
A. Marino, S. R. Cloude, and I. Woodhouse, “Detecting depolarized targets using a new
geometrical perturbation filter,” IEEE Trans. Geosci. Remote Sens., vol. 50, no. 10, pp. 3787-3799,
A. Marino, “A Notch Filter for Ship Detection With Polarimetric SAR Data,” IEEE J. Sel.
Topics Appl. Earth Observ., vol. 6, no. 3, pp. 1219-1232, 2013.
On The Use Of Synthetic Aperture Radar For Hurricanes Applications
1University of Naples Parthenope, Italy; 2Institute of Marine Sciences (ICM-CSIC), Spain; 3Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China; 4National Oceanic and Atmospheric Administration (NOAA-NESDIS), USA; 5Royal Netherlands Meteorological Institute (KNMI), The Netherlands; 6Institut Français de Recherche pour l'Exploitation de la Mer (Ifremer), France; 7Shanghai Ocean University, College of Marine Science, Shanghai 20136, China
Satellite Earth Observation is of paramount importance for a wide range of applications. In fact, the synoptic view of the Earth offered by remotely sensed space-borne measurements allows gathering useful information on climate, environment, etc. Among those applications, the observation of oceans from space represents one of the key topics since oceans cover more than 70% of the Earth’s surface and they are responsible for life. In addition, monitoring the oceans makes us able to better understand natural and human-related processes as marine pollution, climate change, sea level rise, etc.
In this context the synthetic aperture radar (SAR), being a microwave active sensor, routinely provides, information on the Earth’s surface during day and nighttime and in almost any weather condition, with fine resolution and dense revisit time if virtual constellation are exploited.
In this study, European Space Agency (ESA) Sentinel-1 scanSAR Extra Wide Swath (EW) Ground Range Multilook Detected Medium Resolution (GRDM) dual-polarimetric (DP) VH-VV SAR data measurements are considered to extract information, at C-band, on hurricanes. The underpinning idea is to retrieve wind speed both with co-polar and with cross-polar channels. We used a Geophysical Model Function (GMF), the C-band Cross-Polarization Ocean (C-2PO) which is developed for cross-polarized channel and it is independent of incidence angle and wind direction, for the VH channel . With respect to the VV channel, the azimuth cut-off method is studied to calculate a coefficient of linearity, that allows linking directly the azimuth cut-off with wind speed. The link between azimuth cut-off and wind speed is here investigated under extreme wind conditions.
Artificial Lake Monitoring Using Multi-polarization And Multi-temporal SAR Data
1Università degli Studi di Napoli Parthenope, Italy; 2Shanghai Ocean University, College of Marine Science, China
The water-area variations of large lakes are affected by both long-term climate change and short-term localized human activities. In recent years, there has been increasing human activities in large inland lakes worldwide . Within this context, remote sensing plays an important role for lake monitoring. Optical images have the great advantage of being simple to interpret and easily obtainable. However, optical radiation is severely affected by cloud cover, solar illumination, and other adverse meteorological conditions. These problems can be solved using radar sensors, which guarantee all-day and almost all-weather acquisitions, together with a wide area coverage. In particular, Synthetic Aperture Radar (SAR) can be very useful for lake monitoring purposes, because of its fine spatial resolution. Nevertheless, the monitoring using single-polarization SAR data is not simple due to both speckle noise, that makes image interpretability a challenge.
The main goals of this study are to develop multi polarimetric and multi-temporal methods to effectively monitor the change of surface water area of the dam of Monte Cotugno, Basilicata (Italy), the largest embankment dam in Europe. The test site was selected since it is one of the main civil strategic infrastructures of Southern Italy that is severely affected by seepage and leakage.
For this purpose, a method based on the joint use of co- and cross-polarized channels, is used in order to extract the profile of the artificial lake .
Preliminary results are obtained processing a set of dual polarimetric (DP) SAR data collected at C-band from Sentinel-1. The results show that Polarimetric SAR data can be effectively used to detect the changes of the water-level in the artificial lake.
 Ding, X., Li, X. (2011), “Monitoring of the water-area variations of Lake Dongting in China with ENVISAT ASAR images”, International Journal of Applied Earth Observation and Geoinformation, Volume: 13, Issue: 6, Pages: 894-901
 Nunziata F., Buono A., Migliaccio M., Benassai G. (2016), “Dual-Polarimetric C- and X-Band SAR Data for Coastline Extraction" IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (J-Stars), Volume: 9, Issue: 11, Pages: 4921 - 4928
|4:00pm - 5:30pm||C3-ID32437: ECOCRYOHMA|
|HYDROLOGY & CRYOSPHERE|
Inventory and activities of rockglaciers in Northern Tien Shan (Kazakhstan, Krygyzstan, China) using satellite SAR interferometry and optical imagery
1Department of Geography, University of Zurich, Zurich, Switzerland; 2Earth System Science Programme, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, China; 3Gamma Remote Sensing, Gümligen, Switzerland; 4Chair of Cartography, Technische Universität München, Munich, Germany; 5Department of Geosciences, University of Oslo, Oslo, Norway
Rockglaciers are the best visual expression of mountain permafrost and are widespread in the Tien Shan. These ice-debris landforms can, in contrast to permafrost itself, be mapped and monitored directly using remotely sensed data. Previous studies showed that changes in rockglacier flow can be related to climate conditions. However, no consistent rock glacier inventory of the whole Tien Shan exists and information about rockglacier flow is rare. Most previous studies concentrated in a few valleys in the Ile Range of Northern Tien Shan (Kazakhstan).
We have systematically mapped active rock glaciers of Northern Tien Shan located in Kazakhstan, Kyrgyzstan and Xinjiang, China’s north-western-most province, based on differential SAR interferograms and the best available optical imagery from Google Earth or other sources. Different SAR interferograms from various sources, including ERS-1/2, ALOS-1/2 and Sentinel-1, were used to identify and manually map surface deformations at elevations where rockglaciers can occur. The optical imagery were subsequently applied to distinguish rockglaciers from other deformations, e.g. due to subsidence, landsliding or solifluction. The rockglaciers were finally classified according to their state of activity (surface velocity), origin of the debris and topographic parameters (e.g. aspect, slope).
We identified so far more than 700 objects with an extent of about 250 km² within an area of 4000 km². Most of the rockglaciers are moraine-derived and have a northern exposition. The altitude distribution varies significantly depending on the location. Work is ongoing to extend the study region, refine the inventory, classify the rock glaciers according to their activity, and investigate the changes in velocity and surface elevation of selected rockglaciers over time.
Mapping of (rock)glaciers and observation of glacier area and volume changes in High Mountain Asia using earth observation data
1Institute of Tibetan Plateau Research, Chinese Academy of Sciences; 2The Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences
Global warming caused significant changes in mountain glaciers. Observations showed on average clear glacier mass loss. However, recent studies revealed also regions with balanced mass budgets especially in parts of High Mountain Asia (HMA). These heterogeneous changes significantly influence the hydrology, i.e. regionally they alter the river run-off and cause the rise of endorheic lakes on the Tibetan Plateau and globally they affect the sea-level. Glaciers are a major contributor of sea-level rise and affect population that rely on fresh water from glaciers. Rock glaciers have so far only rarely been investigated in HMA but may also of hydrological importance.
The purpose of this sub-project within the more general cryosphere project is to generate an up to date glacier and a rock glacier inventory for selected benchmark regions located in different climatic settings in HMA. Glacier mapping will be based both on optical and radar imagery distributed by the Chinese and European Space programs and combine information about surface flow (as derived in the subproject 2), surface reflectance and backscatter. The generated outlines will be compared to existing ones of previous periods to detect changes in glacier area. As area changes can only indirectly related to climate and hydrology, we will also investigate glacier mass changes using digital elevation models from different time periods (DEM differencing) and altimetry data. Both data sources are complimentary in regard to their spatiotemporal coverage. We will apply ICESat and Cryosat-2 altimetry data to investigate the trends over the whole of HMA and apply DEM differencing in the benchmark regions using existing DEMs (e.g. SRTM, ASTER or TanDEM-X DEMs) or DEMs derived from stereo data. Field measurements and high resolution data will be employed to validate and calibrate the remote-sensing derived results.
The outcome of this project will be improved methodologies for glacier mapping and glacier change assessments and a better knowledge about rock glacier occurrence, the spatial and temporal variability of glacier area and mass changes in HMA, its influence on hydrology and its control by local and climatic forcing. This will be realised thanks to the large archive of satellite data available via Dragon, data available from other sources and thanks to the coordinated effort of the several institutions partnering in the project. The link to hydrology, local and climate forcing will be investigated within this subproject via data assimilation into mass balance models, interaction with the two other sub-projects under the umbrella of cryosphere, and via interaction with the hydrology consortium.
An Assessment of Cloud Detection Methods in High Altitude Snow and Glacial Environments With Sentinel-2
TU Delft, Netherlands, The
Glacier fluctuations are regarded one of the most significant indicators of climate change. The expansion and contraction of glaciers can be observed by outlining glacier boundaries or measuring snow lines with optical Earth observation satellites. New satellites, such as Sentinel-2A/B, provide high spatial resolution images and short revisit times that can be used to make ample measurements to accurately determine glacial variability. Likewise, ever increasing volumes of satellite data make automated boundary and snow line detection a desirable solution for researchers. Two regions of interest for boundary and snow line detection are the Himalaya and Tibetan Plateau. They are home to the world's highest mountains and some of the world's largest non-polar glaciers. These regions also provided valuable water resources to over a billion people in nearby countries, and therefore are not just ecologically, but also economically important. Clouds, however, present a challenge to obtaining useful image data. Mountainous regions are often surrounded or covered by clouds. Clouds can be a menacing phenomenon in remote sensing because they greatly attenuate and reflect short wavelengths used by optical Earth observation satellites. Currently, many techniques exist to automatically detect clouds and classify them. However, they are not perfect. Many techniques have encountered difficulties in cases where snowy and icy landscapes share similar properties with clouds. The Himalaya topographic relief also adds to the challenge. Steep slopes and topographic shadows have a profound effect on surface reflectances and can lead to misclassifications. To address these issues, this study presents an assessment of multiple cloud detection techniques. For initial analysis, 19 Sentinel-2A images were acquired at various times between 12/07/15 and 31/12/16. The images are centered on the Bara Shigri Glacier in Himachal Pradesh, India, a large 10 km long glacier which drains into the Chenab River (an Indus River tributary). The images vary from cloudy to clear (cloud-free), but also have variations in snow cover and cloud shadows. The set was reduced to 6 images that were selected for further classification analysis, as partly shown in Figure 1. Figure 1 shows, starting from the top-left, a natural color image for reference, a manually created cloud mask for validation, and well-known spectral analysis methods: Fmask and maximum likelihood classification. Goal of the study is to first evaluate the performance of existing methods in the automatic identification of pixels contaminated by clouds, and secondly, if necessary, design an improved method, for example, by incorporating the high temporal revisit time of the Sentinel-2 imagery. In doing so, this research seeks to better understand cloud cover over mountainous regions and distinguish them from snow cover and glaciers. It should be noted that cloud detection is a valuable pre-processing step that, when successful, will increase data availability to glacier researchers. Thus, the final goal is to incorporate the cloud-free pixel identification in automated workflows for snow cover studies.
Glacier Motion Monitoring with Sentinel-1A feature-tracking, Kongur Mountain, Pamirs
1Hunan University of Science and Tenchnology, China, People's Republic of; 2State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineer Research Institute; 3Institute for Cartography, Technische Universität Dresden
Catastrophic event - fast moving glacier destroying pastures and killing livestock near the glacier tongue in Kongur Mountains, Xinjiang Uygur Autonomous Region, was reported on May 14th, 2015. In this letter, Sentinel-1 SAR and ALOS/PALSAR data feature-tracking was employed to obtain the glacier surface velocities. Time series of the estimated glacier surface velocities suggested that the left tributary had been a fast moving flow for eight years at least. Analysis of the obtained glacier surface velocities Variation made the surge occurrence confirmed, and from Mar 24th, 2015 to May 11th, 2015, the left tributary has pushed the trunk gradually detected by the analysis of glacier flow vector. Surface velocities of three stages, prior to the surging, during surging and post surging were mapped and analyzed. This research suggested that monitoring glacier surface velocities could be regarded as an effective way for glacier catastrophic warning.
Recent accelerating mass loss of southeast Tibetan glaciers and the relationship with changes in macroscale atmospheric circulations
Chinese Academy of Sciences, China, People's Republic of
The mass balance history (1980–2010) of a monsoon-dominated glacier in the southeast Tibetan Plateau is reconstructed using an energy balance model and later interpreted with regard to macroscale atmospheric variables. The results show that this glacier is characterized by significant interannual mass fluctuations over the past three decades, with a remarkably high mass loss during the recent period of 2003–2010. Analysis of the relationships between glacier mass balance and climatic variables shows that interannual temperature variability in the monsoonal season (June–September) is a primary driver of its mass balance fluctuations, but monsoonal precipitation tends to play an accentuated role for driving the observed glacier mass changes due to their covariation (concurrence of warm/dry and cold/wet climates) in the monsoon-influenced southeast Tibetan Plateau. Analysis of the atmospheric circulation pattern reveals that the predominance of anticyclonic/cyclonic circulations prevailing in the southeastern/northern Tibetan Plateau during 2003–2010 contributes to increased air temperature and decreased precipitation in the southeast Tibetan Plateau. Regionally contrasting atmospheric circulations explain the distinct mass changes between in the monsoon-influenced southeast Tibetan Plateau and in the north Tibetan Plateau/Tien Shan Mountains during 2003–2010. The macroscale climate change seems to be linked with the Europe-Asia teleconnection.
Lake volume and groundwater storage variations in Tibetan Plateau’s endorheic basin
1Chinese Academy of Sciences, China, People's Republic of; 2Department of Geography, University of Zurich
The Tibetan Plateau (TP), the highest and largest plateau in the world, with complex and competing cryospheric-hydrologic-geodynamic processes, is particularly sensitive to anthropogenic warming. The quantitative water mass budget in the TP is poorly known. Here we examine annual changes in lake area, level, and volume during 1970s −2015. We find that a complex pattern of lake volume change during 1970s−2015: a slight decrease of –2.78 Gt yr-1 during 1970s−1995, followed by a rapid increase of 12.53 Gt yr-1 during 1996−2010, and then a recent deceleration (1.46 Gt yr-1) during 2011−2015. We then estimated the recent water mass budget for the Inner TP, 2003−2009, including changes in terrestrial water storage (TWS), lake volume, glacier mass, snow water equivalent (SWE), soil moisture, and permafrost. The dominant components of water mass budget, namely changes in lake volume (7.72 ± 0.63 Gt yr-1) and groundwater storage (5.01 ± 1.59 Gt yr-1), increased at similar rates. We find that increased net precipitation contributes the majority of water supply (74%) for the lake volume increase, followed by glacier mass loss (13%), and ground ice melt due to permafrost degradation (12%). Other term such as SWE (1%) make a relatively small contribution. These results suggest that the hydrologic cycle in the TP has intensified remarkably during recent decades.
|4:00pm - 5:30pm||D3-ID32431: Seismic Detection from InSAR|
|SOLID EARTH & DISASTER RISK REDUCTION|
InSAR monitoring of ground motion in response to climatic or tectonic forcing : from the exploitation of the Envisat archive to the processing of the recent Sentinel-1 database over the tibetan plateau
1ISTerre, CNRS, Université Grenoble-Alpes, Grenoble, France; 2UCLA, Los Angeles, USA; 3Laboratoire de Géologie de Lyon, Terre, Planètes et Environnement, Lyon, France; 4Institute of Geology, China Earthquake Administration, Beijing, China; 5Pekin University, Beijing, China
Multitemporal interferometric synthetic aperture radar (InSAR) observations have been widely used to characterize spatial and temporal variations of ground deformation of tectonic, climatic or anthropic origin. An accuracy in the order of a millimeter per year on velocity measurements can be achieved in areas where a dense archive of InSAR data exists, and when methodological developments are applied to enhance coherence and improve the signal to noise ratio. With systematic acquisitions and a revisit time of 24 days over Tibet, the new Sentinel-1 radar data offer new perspectives to retrieve small deformation signal and better separate various sources of deformation. We review here our most recent studies over the tibetan plateau, emphasing improvments in InSAR processing of both the Envisat archive and newly acquired Sentinel-1 data.
We characterize the ground motion induced by the response of the permafrost active layer to climatic forcing, over a 60000m2 area in the northwestern part of the tibetan plateau, during 8 years spanned by the Envisat archive. This phenomena is limited to Cenozoic sedimentary basins and is spatially variable in both its seasonal amplitude (2.5–12 mm) and multiannual trend (−2 to 3 mm/yr). A degree-day integrated model adjusted to the data indicates that subsidence occurs when the surface temperature exceeds zero (May to October) over areas where seasonal movements are large (>8 mm). The period of subsidence is delayed by 1–2 months over areas where smaller seasonal movements are observed, suggesting an unsaturated soil where water occurs in the deeper part of the active layer. We use the same Envisat archive to characterize the interseismic strain pattern across the Altyn Tagh fault system. The previous permafrost study helps better unwrapping interferograms and referencing velocity maps on adjacent tracks, which leads to a better quantification of the tectonic signal. Here we also test various strategies to correct tropospheric delays, improving as well the differentiation between secular tectonic deformation and seasonal signals. A linear feature of strain localization (1-2 mm/yr of velocity change in the line of sight -LOS-) is identified north of the Altyn Tagh strike-slip Fault (ATF) within the Tarim basin, parallel to the ATF. We suggest that the ATF is connected at depth with a transpressive ramp emerging north of it in the basin, both structures accommodating by slip partitioning an oblique (N52°E) convergence rate of 14.2 mm/yr. South of the ATF, we also observe strain localization along a continuous feature, possibly the Jinsha suture, corresponding to 3 mm/yr of velocity change in the LOS. Finally, taking advantage of our experience in InSAR processing of long-tracks, small deformation and difficult terrain conditions areas, we adapt our chain to the processing of Sentinel-1 (S1) data, focusing on the eastern-southeastern border of the tibetan plateau, from the Haiyuan fault to the north to the Xian Shui He fault to the south.
Retrieve near-field deformation of large earthquakes from Sentinel-1 radar interferometry data
1Institute of Geology, China Earthquake Administration; 2School of Earth and Space Sciences, Peking University, China
It is challenging to effectively extract the near-field deformation of large earthquakes using InSAR approach, especially from the short-wavelength radar sensors, such as the C-, X- band systems. The issue leads to incomplete deformation field of large earthquakes in the vital regions, which are critical for earthquake studies. Some of the well-known decorrelation effects could lead to signal loss and prevent successful phase unwrapping, such as the geometric (or spatial), temporal, and Doppler decorrelation, etc. The decorrelation effects may reduce the received energy of satellite radar sensors from the back-scattering of ground targets. Hence, the incoherence (or partial of it) of radar signals will greatly reduce the signal-to-noise ratio of InSAR phase and leads to information loss in the deformation field or serious phase jumping issues in the final products. In the near-field of large earthquakes, high phase gradient may be irresolvable by traditional unwrapping methods. In extreme situations, the complete incoherence of radar returns could occur when the phase difference of neighbor pixels exceedingπradians. Except for this physical limitation of the radar systems, it is possible to extract useful information from InSAR data. Moreover, severe DEM errors (depending on baselines and topography) will also greatly influence the phase unwrapping process and introduce heavy phase jumping errors, leading to unreliability of InSAR observations.
To overcome the limitations described above, we developed a simple strategy for phase unwrapping. Due to strong phase gradient following large earthquakes, we first multi-look the InSAR phase to a lower resolution and implement conventional Goldstein filtering and unwrapping. After the step, we use a 2-D spatial filter to estimate the first order deformation signals and remove this component from the unwrapped phase. We do the same procedure in an iterative way until it is impossible to unwrap the residual phase. The final residual phase plus the filtered-out phase using Goldstein filter are deemed as the total residuals for the wrapped phase. We then resample the total residuals to the original spatial resolution of InSAR phase and removed it from the observations. Then the conventional unwrapping procedures will be able to used for extracting InSAR phase covering even the near-field of earthquake deformation area. The total residuals could also include useful information excluded from earthquake deformation, such as localized deformation of landslides, small areas of uplift or subsidence, besides the DEM error phase.
We had successfully applied the method to some large earthquakes, such as the 2015 Illapel, Chile earthquake, the 2016 Ecuador earthquake, the 2016 Central Itlay earthquake sequence, and the 2016 New Zeland earthquake, etc. So far, we only consider the Sentinel-1 data here, due to its small temporal decorrelation effects, but it would be much easier to work with L-band data, such as ALOS-1/2. Also, in some mountainous regions, it is also valuable to use the method to overcome the phase unwrapping issues for interseismic or postseismic InSAR phase retrieval.
The Ganzi segment of the Xian Shui He fault system : present-day behavior constrained by time serie analysis of Sentinel-1 InSAR data
1ISTerre, CNRS, Université Grenoble-Alpes, Grenoble, France; 2Laboratoire de Géologie de Lyon, Terre, Planètes et Environnement, Lyon, France; 3Institute of Geology, China Earthquake Administration, Beijing, China; 4Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
In eastern Tibet, the left-lateral, ~1400 km-long, Xianshuihe fault system (XFS) is oneof the most tectonically active intra-continental fault system in China. More than 20 M>6.5 earthquakes broke this fault since 1700, including the recent 2010 Mw6.9 Yushu earthquake. We focus here on the northwestern segment of the XFS, the Ganzi fault, east of the Yushu rupture, identified as a seismic gap capable of producing Mw7.6 earthquakes. The Quaternary slip-rate of this Ganzi segment is estimated to 6-8 mm/yr, from offsets measurements and cosmogenic dating of moraine crests and alluvial fan edges (Chevalier et al., 2017). To characterize the present-day behavior of this segment, we process the first two-years of Sentinel-1 InSAR data to produce an average velocity map across the Ganzi fault, using both descending and ascending data. We adapt our InSAR processing chain (NSBAS) to the specificities of Sentinel-1 data and produce a simple elastic model of the InSAR-derived velocity field. We discuss our first results in comparison with the existing GPS data and the long-term tectonic setting.
|4:00pm - 5:30pm||E3-ID32194: Crop Mapping|
|LAND & ENVIRONMENT|
Crop mapping with the Chinese and European satellite data
1NSMC, China, People's Republic of; 2Ningxia Meteorological Science Institute, China, People's Republic of
The satellite data application in agricultural has a long history. The new
Orchard mapping in Ningxia with the high resolution Chinese satellite data
1Ningxia Meteorological Science Institute; 2NSMC, China, People's Republic of; 3University of Electronic Science and Technology of China
Abstract: The orchard is developing very fast in Ningxia Hui autonomous region in Northwest China with the development of wine brewing Companies in recent year. Agrometeorological monitoring for the growth of grapes and other fruit trees is one of key process to identify the high quality fruit in the region but there is lack of the baseline map of orchard in Ningxia. This study aims at developing an orchard map in Ningxia in support of the agrometeorological service. The study collected high resolution GF satellite as much as possible which resolutions are around 8 t0 16 meters for multispectral bands. The decision tree was used to classify the images. All classified images were merged and finally an orchard map was formed. The validation was conducted with the field data.
|6:30pm - 8:30pm||ESA Hosted Social Event|
|8:30am - 10:00am||A4: Project Result Summaries|
|ATMOSPHERE - CLIMATE - CARBON|
|8:30am - 10:00am||B4-ID31451: Oceanic and Atmospheric Processes|
|OCEANS & COASTAL ZONES|
Project 31451, Subproject “Upwelling”. Results after 1 year's activity
1University of Hamburg, Germany; 2University of Hamburg, Germany; 3South China Sea of Oceanology
1) In the first year a journal paper was completed, which was initiated during Dragon 3 within the project OPAC with the title “Oil spill detection by imaging radars: challenges and pitfalls” by Werner Alpers (University of Hamburg, Ben Holt (JPL/NASA), and Kan Zeng (Ocean University of China). It has been submitted to “Remote Sensing of Environment” and is presently undergoing a second review.
2) The Envisat and Sentinel-1 archives have been screened extensively for radar signatures of upwelling in Chinese waters and a large number of synthetic aperture radar (SAR) images showing such signatures have been identified.
3) For several prominent cases SAR images showing radar signatures of upwelling have been compared with SST, Chl-a images and with sea surface wind field maps retrieved from Quikscat and ASCAT.
4) Upwelling events at the east coast of Hainan have been compared with model results obtained by the HAMSON model.
5) Upwelling induced by the typhoon Soudelor (July/August 2015), which was the strongest tropical cyclone of the 2015 Pacific typhoon season, has been studied, which gave rise to plankton bloom and an eddy-like Chl-a concentration pattern.
6) The Chinese Ph. D. student Zheen Zhang, who is supervised by Thomas Pohlmann of the University of Hamburg, will carry out in the next year simulations with the MITgcm model with the aim to show that internal waves can be generated by upwelling. The focus will be on the upwelling area at the east coast of Hainan.
7) No exchange of European and Chinese partners could be arranged in the first year of the project.
Typhoon Wind-pimp Effects on Marine Ecosystem in the South China Sea (Project 31451, Subproject “Upwelling” Results after 1 year's activity)
1Chinese Academy of Sciences, China, People's Republic of; 2Institute of Oceanography, University of Hamburg, Germany
Typhoons have very strong “Wind-Pump” effects on marine ecosystem, via inducing upwelling and vertical mixing. This paper introduces our recent related studies using satellite remote sensing data.
1, Typhoon wind-pump effects on air-sea CO2 flux
In-situ oceanographic measurements were made before and after the passage of Typhoon Wutip in September 2013 over the northern South China Sea (SCS). The surface geostrophic circulation over this region estimated from satellite altimetry data features a large-size anti-cyclonic eddy, a small-size cyclonic eddy, and smaller-size eddies during this period. Significant typhoon-induced changes occurred in the partial pressure of CO2 at the sea surface (pCO2sea) during Wutip. Before the passage of Wutip, pCO2sea was about 392.92±1.83, 390.31±0.50, and 393.04±4.31 μatm over the cyclonic eddy water, the anti-cyclonic eddy water, and areas outside two eddies, respectively. The entire study region showed a carbon source (1.31±0.46 mmol CO2 m-2 d-1) before Wutip. In the cyclonic eddy water after Wutip, high sea surface salinity (SSS), low sea surface temperature (SST), and high pCO2sea (413.05±7.56 μatm) made this area to be a carbon source (3.30±0.75 mmol CO2 m-2 d-1). In the anti-cyclonic eddy water after Wutip, both the SSS and SST were lower, pCO2sea was also lower (383.03±3.72 μatm), and this area became a carbon sink (-0.11±0.55 mmol CO2 m-2 d-1), in comparison with the pre-typhoon conditions. The typhoon-induced air-sea CO2 flux reached about 0.03 mmol CO2 m-2 d-1. Noticeable spatial variations in pCO2sea were affected mainly by the Wind-pimp Effects - typhoon-induced mixing/upwelling and vertical stratifications.
Our study suggests that the impact of the typhoon Wind-pimp on the local air-sea CO2 flux is highly correlated with the oceanographic conditions during the typhoon.
2. Upwelling effecting Distribution characteristics of phytoplankton size structure in the western SCS in summer
Driven by the southwest monsoon, an offshore jet is usually formed in western South China Sea (SCS) and sandwiched by a cyclonic eddy in the north and an anti-cyclonic eddy in the south, which effects ecosystem of the region. Using in-situ and satellite data in September 2014, the present study analyze the joint impact of this jet with two eddies on phytoplankton size structure in this region. The data showed that picophytoplankton (0.2-2µm) dominated the surface, taking average 76.7% of total chlorophyll. The contribution of nanophytoplankton (2-20µm) and microphytoplankton（20-200µm）in jet area was respectively higher and had a positive relationship with total chlorophyll. Comparatively higher percentage of microphytoplankton appeared in anti-cyclonic eddy in surface (av.10.3%) than in cyclonic eddy (av.3.6%). The results suggest that physical processes significantly influence summertime surface phytoplankton size structure in western South China Sea. Both jet and eddies can effect phytoplankton size structure by increasing the contribution of microphytoplankton. Surface horizontal advection of phytoplankton by northeastward jet form the coastal upwelling area is the main source of microphytoplankton in open sea. The interactions of convergence and divergence in eddies with jet form a chlorophyll front and increase the microphytoplankton component. Upwelling in the center cyclonic eddy bring up nutrients which raises microphytoplankton component.
3．Mixed layer depth responses to tropical cyclones in the northeastern SCS
Utilizing the vertical profiles of temperature and salinity data obtained by Argo floats and multi-source satellite remote sensing data, including sea surface temperature (SST) and sea surface wind fields, combined with the National Centers for Environmental Prediction (NCEP) Ⅱ reanalysis data, we analyzed changes of mixed layer depth (MLD) in the northeastern South China Sea (SCS) in responses to tropical cyclones Kalmaegi (typhoon) and Fung-Wong (tropical storm), which passed the SCS in succession in mid and late September 2014. The results indicate that the maximum net heat flux (upward into the air) increased from 170 to 400 W·m–2 at the air-sea interface, caused the maximum SST cooling of 3℃ by the “wind pump” effect after Kalmaegi and Fung-Wong passed through. The “cold wake” induced by Kalmaegi lasted for more than 10 days thanks to the following tropical storm Fung-Wong, indicating the effect of superposition in SST cooling. MLD was deepened from 23 to 50 m in the “cold wake” one day after Kalmaegi passed by. MLD was deepened from 31 to 91 m eight hours after Fung-Wong passed by, due to the coastal upwelling induced by offshore Ekman transport driven by wind stress at the southwestern of Taiwan Island. After the tropical cyclones passed by, salinity profile in the mixed layer showed uniformity later than temperature profile, and recovered earlier than temperature profile, revealing the time lag in mixed layer responses. For the spatial variation response to the two tropical cyclones, the changes of SST and MLD were larger on the right-hand side of the tropical cyclones (along the moving directions of tropical cyclones) than on the left-hand side. The uneven deepening even shallowing in MLD in the cold wake may reveal that different depths of deep cold water uplifted by the vertical current switch between upwelling and downwelling in the Ekman layer due to the change of Ekman pumping velocity
Sea Surface Temperature (SST) in South China Sea Retrieved from Chinese Satellite FY-3B VIRR Data
1south China Sea Institute of Oceanology,CAS, China, People's Republic of; 2University of Chinese Academy of Sciences, China, P.R.; 3The Guangdong Ecological meteorological Center, Guangzhou, China
Sea Surface Temperature (SST) in South China Sea Retrieved from Chinese Satellite FY-3B VIRR Data
Chuqun CHEN(1)(2)*, Quanjun HE(3)**, Shilin TANG (1)(2)***,Haibin YE(1)
(1) State key Lab of Tropical Oceanography，South China Sea Institute of Oceanology, Chinese Academy of Sciences,164 West Xingang Road, Guangzhou, China, 510301.
(2) University of Chinese Academy of Sciences，19A Yuquan Road, Beijing, China,100049.
(3) The Guangdong Ecological meteorological Center, 312 Dongguanzhuang Road, Guangzhou, China, 510080.
In the surface layer of the ocean, Sea Surface Temperature (SST) is the most important parameter, which is widely applied for studying water masses, air-sea interaction, marine ecosystem and environment, and other subjects. In decades, a great many satellites with thermal infrared sensors have been launched and huge thermal infrared remote sensing data were collected for detection of SST. With the continuous improvement on accuracy, the satellite remote sensing technique has become the dominant approach for SST detection.
In this report, the thermal infrared data collected by FY-3B were employed for retrieval of SST in the South China Sea. FY-3B is one of the second generation of Chinese meteorological satellite on polar orbit, it has VIRR (Visible Infrared Radiometer) sensor with 10 bands, of which, band 4 covers 10.3~11.3um and band 5 covers 11.5~12.5um, similar to NOAA/AVHRR.
The ship-measured SST dataset in 2011 and 2012 were collected and totally 20607 (of which 11419 in daytime and 9188 in nighttime) of the ship-measured SSTs were selected on consideration of the quality, the measurement time and the measurement location matching with cloudy-free Fy-3B data. Based on the well matched ship-measured SST and FY-3B VIRR data, a non-linear SST (NLSST) algorithm was developed and applied for retrieval of SST in the South China Sea. The monthly mean SST distribution image maps of South China Sea were integrated. The monthly mean SST image maps show that the maximum monthly mean SST occurs in June, although in July and August there is a stronger solar heating. It possibly due to the monsoon-induced mixing, which results in lower SST.
Keywords: FY-3B satellite, Visible Infrared Radiometer (VIRR), Sea Surface Temperature (SST), South China Sea.
本报告介绍利用中国第二代极轨气象卫星“ 风云三号气象卫星”的第二颗卫星（FY-3B）数据反演南海海面温度。FY-3B于2010年11月发射，其可见红外辐射计（Visible Infrared Radiometer-VIRR）具有与NOAA/AVHRR传感器类似10个波段，其中的热红外波段（4）和（5）的波段范围分别为10.3~11.3（μm）和11.5~12.5（μm）。
Sentinel-1 coastal wind over Taiwan
1ifremer, France; 2Collecte Localisation Satellite, France; 3Nanjing University of Information Science and Technology, China; 4National Ocean Technology Center, China
Sentinel-1 A & B perform acquisitions over Taiwan island. To date, this data are not routinely processed up to Level-2 OCN product by Sentinel-1 ESA PDGS. This paper considers the complete archive of Sentinel-1 data acquired over Taiwan and proposes a new algorithm for wind inversion in coastal areas. It relies on a two steps process. The first one aims at extracting wind direction and filtering out non-wind related signatures in both co- and cross- polarized channels. The second one combines these information and the radar cross-section from the two channels to retrieve wind speed and direction at high resolution.
The complete Sentinel-1 SAR archive is processed with this new algorithm. Results are presented and will be made available to the public. The buoys network around Taiwan island is used as reference for the ocean surface wind. SAR wind speed and direction are compared to in-situ buoys and atmospheric model winds. The choice of the GMF to be used for wind inversion is discussed.
The occurrence and the location of the non-wind signature are also presented and tentatively related to other oceanic or meteorological phenomena such as rain or bloom.
Can Sentinel-1 help Typhoon Monitoring ?
1ifremer, France; 2Nanjing University of Information Science and Technology, China; 3National Ocean Technology Center, China; 4Collecte Localisation Satellite, France
During summer 2016, ESA set up SHOC (for Satellite Hurricane Observations Campaign) campaign dedicated to hurricane observations with Sentinel-1 SAR in both VV and VH polarizations acquired in wide swath modes. Among the 70 Sentinel-1 passes scheduled by ESA mission planning team, more than 20 observations over hurricane eyes were acquired and Tropical Cyclones (TC) were captured at different development stages. The sensitivity difference of VH and VV Normalized Radar Cross Section (NRCS) to the response of the ocean surface to tropical cyclones is analyzed. In particular, during Lester hurricane most intense phase (when the track files indicates wind speeds of 120 knots), the sensitivity of the VH-NRCS computed at 3-km resolution is found to be more than 3.5 times larger than in VV. In addition, taking opportunity of SAR high resolution, we also show that the decrease in resolution (up to 25 km) does not change dramatically the sensitivity difference between VV and VH polarizations. This clearly opens perspectives for MetOp-SG SCA, the next generation C-band scatterometer with co- and cross-polarization capability. VV and VH channels are combined to get ocean surface wind vectors from Sentinel-1 dual-polarized Level-1 products. SAR winds are compared at 40-km resolution against L-Band SMAP radiometer winds with co-locations less than 30 minutes. The wind speed obtained using both VH and VV polarization is found to be more consistent with SMAP than wind obtained in co-polarization for wind speeds larger than 25 m/s. Based on radiometer winds, a new GMF (MS1A) is proposed. It improves the consistency between 40-km SAR winds and SMAP winds. The method is applied to Megi and Lyonrock Typhoon and results presented in this paper.
|8:30am - 10:00am||C4-ID32439: MUSYCADHARB (part 2)|
|HYDROLOGY & CRYOSPHERE|
Development of a Water and Enthalpy Budget-based Glacier mass balance Model (WEB-GM) and its preliminary validation
1Institute of Tibetan Plateau Research, Chinese Academy of Sciences, China; 2CAS Center for Excellence in Tibetan Plateau Earth Sciences, China; 3Department of Earth System Science, Tsinghua University, China
This paper presents a new water and energy budget-based glacier mass balance model. Enthalpy, rather than temperature, is used in the energy balance equations to simplify the computation of the energy transfers through the water phase change and the movement of liquid water in the snow. A new parameterization for albedo estimation and state-of-the-art parameterization schemes for rainfall/snowfall type identification and surface turbulent heat flux calculations are implemented in the model. This model was driven with meteorological data and evaluated using mass balance and turbulent flux data collected during a field experiment implemented in the ablation zone of the Parlung No. 4 Glacier on the Southeast Tibetan Plateau during 2009 and 2015–2016. The evaluation shows that the model can reproduce the observed glacier ablation depth, surface albedo, surface temperature, sensible heat flux, and latent heat flux with high accuracy. Comparing with a traditional energy budget-based glacier mass balance model, this enthalpy-based model shows a superior capacity in simulation accuracy. Therefore, this model can reasonably simulate the energy budget and mass balance of glacier melting in this region and be used as a component of land surface models and hydrological models.
Melt and Surface Sublimation across a Glacier of the Tibetan Plateau: Distributed Energy Balance Modelling of the Parlung No. 4 Glacier and Comparison of Scales
1Northumbria University, United Kingdom; 2ETH Zurich; 3Institute of Tibetan Plateau Research; 4Delft University of Technology
Most estimates of melt and surface sublimation rates for the glaciers of the Tibetan Plateau have been obtained at the point scale, and it is not entirely established how ablation components vary across the entire extent of a glacier in this environment. Energy balance models can provide accurate simulations of energy fluxes and ablation components, thus fostering understanding of the main processes at the glacier-atmosphere interface, but need a high number of meteorological and surface input variables that can be available at the point scale of Automatic Weather Stations but are difficult to extrapolate across the distributed domain of an entire glacier.
Here, we simulate the distributed energy and mass balance of Parlung No. 4 Glacier, for the ablation season 2016, using a distributed energy balance model. We use input data at one AWS and two novel methods, which combine in-situ and reanalysis data, to generate fields of near-surface air temperature and wind speed that are needed to force the model. We calculate the spatial distribution of energy fluxes and ablation rates over the glacier surface at a high spatial resolution (50 m), which allows the inclusion of small-scale processes, such as katabatic and valley winds, refreezing and topographic shading, and knowledge of the local variability of topographic parameters, such as sky-view factors and local slopes.
We also compare our model results with the simulations of a point-scale energy-balance model based on enthalpy calculations which includes advanced schemes for calculation of albedo and turbulent fluxes; and with large-scale, regional energy balance simulations driven by satellite input data. The model is validated with in-situ and satellite observations of ablation, surface temperature and turbulent fluxes.
Our main objectives are to: i) advance our understanding of glacier ablation in the Tibetan Plateau by providing one of the first spatially-distributed quantifications of energy fluxes and ablation rates on a glacier in this region, including understanding the role that surface sublimation plays; ii) explore the use of two relatively new methods to generate fields of air temperature and wind speed, which provide alternatives to solve some of the interactions between large-scale meteorological forcing and the atmospheric boundary layer over a mountain glacier during the summer period; and iii) understand the level of model complexity that is needed for accurate simulations of energy fluxes and ablation components at different spatial scales.
Monitoring Water resources in Red River Basin using Microwave Remote Sensing
1isardSAT, Spain; 22Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences; 3CESBIO, Toulouse, France
The project is focusing on monitoring water resources in the Red River basin using microwave remote sensing. The Red River, also known as the Yuan River in Chinese, is a trans-boundary river basin with its total area of 169,000km2 shared by Vietnam (51%), China (48%) and Laos (1%). The Red River basin has a tropical or subtropical climate, dominated by the southwest monsoon from May to September and the northeast monsoon from October to April. The monsoon results in massive flow volume fluctuations. Flooding is a significant problem during the rainy season, particularly in July and August. At the same time, large area of karst landform causes the river flow loss and water shortage. One of the greatest challenges for flood prediction and integrated water management in the Red River basin is a lack of information on reservoir management as a consequence it is not easy to estimate the water resources. Since it is a trans-boundary river, there are difficulties to manage the area as a whole, and the information might not be in time for flood and drought early warning.
Hydrological data on major rivers, lakes and wetlands can often be difficult to obtain due to a region's inaccessibility, sparse distribution of gauge stations or the slow dissemination of data. Remote sensing technologies can be used to overcome such shortcomings.
The main objective of this project is to develop the algorithms and synergies between different Microwave Remote Sensing sensors to be able to monitoring water resources in the Red River Basin. For that purpose, the water elevation information, precipitation, soil moisture and evapotranspiration by remote sensing will be integrated in a hydrological model to improve its accuracy.
In this presentation we will be showing the first results of the variables monitored during this first year.
|8:30am - 10:00am||D4: Project Result Summaries|
|SOLID EARTH & DISASTER RISK REDUCTION|
|8:30am - 10:00am||E4-ID32248: Urban Services for Smart Cities|
|LAND & ENVIRONMENT|
Fine Scale Estimation of the Discomfort Index in Urban Areas in View of Smart Urbanization
National and Kapodistrian University of Athens, Greece
The discomfort index (DI) is an important indicator that measures human heat sensation for different climatic conditions. Currently, the DI of a city is usually calculated using a few weather stations and hence does not accurately represent various thermal discomfort states of the city as a whole. This is a considerable drawback taken the importance of the index for assessing the quality of life within urban agglomerations and thus facilitating measures for smart urbanization. In this study a technique to produce fine-scale DI maps is proposed and applied accordingly. The technique is based on the combination of Sentinel-2 and Landsat 8 images with in-situ measured meteorological data. The DI map clearly reveals the spatial details of the DI in different locations of the city and thus supports focused interventions with the potential to support the operation of a city as smart.
Spatial downscaling research for urban land surface temperature based on the A-SVM method
1Key Laboratory of Environmental Change and Natural Disaster, Ministry of Education, Beijing Normal University,China, People's Republic of; 2Faculty of Geographical Science, Beijing Normal University, China, People's Republic of
Urban land surface temperature (LST) is an important parameter. However, due to the contradiction between the temporal and spatial resolution of thermal infrared remote sensing data, it’s difficult to obtain high temporal- spatial resolution LST data simultaneously. In order to solve this problem, this author considered multiple city characteristical parameters and used a simple model that can adjust the spatial distribution of scaling factors, combining with the SVM model to establish a new surface temperature spatial downscaling method which was suitable for city surface, named A-SVM.
In this paper, Beijing was chose as research area. The author divided the study into four steps. Firstly, correlation analysis and PCA (Principal Component Analysis) were used to select the parameters strongly related-to LST but independent respectively as the regression kernels (scaling factors) to do downscaling regression. The result shows that there are 6 factors were selected to do SVM regression, namely NDVI, UI, MNDWI, VAP, BAP and WAP. Screening of scale factors is the basis of SVM and A-SVM methods.
Secondly, three methods were used to verify the accuracy of the A-SVM model, which are direct resampling, TsHARP method and SVM model. The direct resampling method is a strategy that does not use any auxiliary data to directly resample a low-resolution image to a high spatial resolution. The TsHARP method is an improvement to the DisTrad quadratic model, using the negative correlation between NDVI and LST, and its basic assumption is that the linear relationship between LST and NDVI is scale invariant. SVM is a newer statistical learning theory proposed by Vapnik. Using the SVM model for low resolution to high resolution, replacing the low-resolution scale factors to high-resolution scale factors and further adding the model estimation error，high-resolution LST can be obtained.
There is a simple model to dynamically adjust the scale factor spatial distribution according to the Standard Deviation of scale factors from high resolution and low resolution LST. A-SVM model was built based on this method and SVM model. By considering the relationship between high-resolution and low-resolution images, the purpose of the model-building is to make the remote-sensing indices of the high spatial resolution image have the same spatial distribution as those of the low spatial resolution image, which will reduce the downscaling estimation error of different resolutions.
Finally, the author got the results of retrieved LST from four methods and the scatter diagram of estimated 120m LST from four methods against the LST received from TM. The 120m LST which was directly retrieved from TM thermal infrared band was selected as the real LST and verification data. Results shows that the improved method could obtain ideal downscaling results, whose RMSE was 1.82 K, R2 was 0.85, and ERGAS index achieved 0.07, and it was superior to the direct resampling method, the classical method TsHARP and the SVM method whose scaling factors were unadjusted.
Through this research, this author got two important conclusions:
(1)To reflect the complex characteristics of urban surface, multiple related parameters with LST including NDVI, UI, MNDWI,VAP,BAP,WAP were chosen as the scaling factors based on the correlation and PCA analysis, which can partly show the change of urban LST and avoid redundancy phenomenon between each other.
(2) Based on the 6 kinds of scaling factors, a new adjusted-SVM spatial downscaling method for urban land surface (A-SVM) was developed combining the SVM model with a space distribution adjustment model, which could avoid the ideal assumptions that the relation between scaling factors and LST was invariant. The validation result shows A-SVM method can get the better prediction precision.
Αssessing the Spatial Distribution of Thermal Spots in Support of Smart Urbanization
National and Kapodistrian University of Athens, Greece
Urbanization affects considerably the thermal environment of cities and influence the spatial and temporal consumption of energy for heating and cooling. The increase of impervious surfaces alongside with the reduction of vegetated areas lead to increased air and surface temperatures. Remote sensing data is suitable for up-to-date urban land use mapping and for the assessment of the thermal environment of urban areas. In this study a statistical approach is developed on the basis of satellite data, in order to identify the areas where maximum and minimum temperature values are observed; the approach is tested for the city of Athens, Greece. The recognition of such areas is important as they reflect areas where immediate interventions are necessary to ameliorate the thermal environment, whereas the knowledge of their spatial distribution and temporal variations is needed for smart urbanization.
Feature Extraction On POLSAR Images For Detection Of Anthropogenic Extents
Università degli Studi di Pavia, Italy
This abstract presents a detailed application of feature extraction methods on PolSAR records for built-up area identification. This work aims at providing a thorough description of the multivariate patterns insisting on roll-variant and roll-invariant quad-POLSAR features.
Indeed, the detection and classification of urban areas in the instantaneous field of view can take a great advantage from processing the whole amount of records and parameters obtained from POLSAR images. In fact, multivariate processing is used to deliver a thorough understanding of the relationships and regularities that can be retrieved over the selected areas for each target class. Hence, the rationale for employing both roll-variant and roll-invariant features is the intimate involvement of all the attributes acquired by POLSAR remote sensing with the anthropogenic extents distribution, which is used to provide a complete characterization of the built-up areas and of the hidden regularities lying within the records as well.
In order to provide such a multivariate analysis for feature extraction, two methods which aim at retrieving a solid recognition of significant patterns within the dataset have been taken into account. First, we employed a method named Hierarchical Binary Decision Tree (HBDT) , which combines different processing chains (made by a feature selection and a classification step) and automatically adapts to the spatial (and spectral) properties of the classes available in the scene. Typically, in homogeneous decision trees, at each node the same algorithm is used for separation between groups of classes. In our case, the most useful processing chain, composed by the most suitable feature set and the most efficient classifier, is selected per each node. This selection is performed by computing an intermediate accuracy assessment for each processing chain. Only the feature set (or its most noiseless subset) and classifier pair that produces the best result is selected and assigned to the node. The procedure is then repeated removing the already identified class/classes until all the nodes are identified.
Moreover, we considered a method based on mutual information maximization to explore the dataset in order to detect relevant patterns for built-up area extraction . Specifically, the method that has been developed aims at providing a identifying affinity patterns, which better describe each class within the considered dataset. Good classification performances are obtained by selecting patterns fulfilling the Pareto optimality and by properly modeling a combination of the information provided by each pattern. Since the proposed approach is completely data driven and relies on information theory-based quantities, it is very flexible and totally independent from the statistics of the classes, and allows exploring datasets consisting of heterogeneous features.
Two datasets acquired by Radarsat-2 Quad-PolSAR sensor over the San Francisco area have been considered for testing. Specifically, they consist of 28 and 113 roll-invariant and roll-variant features, respectively. The aforementioned algorithms have been used to investigate the POLSAR records in order to obtain a precise characterization of the patterns that describe anthropogenic extents in the considered area. In order to accurately assess the detection and classification performance of the aforesaid methods, we analyzed the considered datasets by means of algorithms relying on a different approach. Specifically, we used methods based on ensemble learning  (such as random cluster ensemble and recursive feature elimination scheme) in order to explore the relationships among the data. Results show that the methods relying on the multiple feature pattern recognition are able to provide accurate extraction of built-up areas over both the considered datasets. Indeed, they are able to outperform existing algorithms while guaranteeing acceptable computational complexity costs, so that they represent a valid option for POLSAR feature extraction applied to identification of built-up areas.
Land subsidence prediction in Beijing based on PS-InSAR technique and improved Grey-Markov model
Capital Normal University, China, People's Republic of
Land subsidence induced by excessive groundwater withdrawal has caused serious social, geological, and environmental problems in Beijing. Rapid increases in population and economic development have aggravated the situation. Monitoring and prediction of ground settlement is important to mitigate these hazards. In this study, we combined persistent-scatterer interferometric synthetic aperture radar (PS-InSAR) with Grey system theory to predict the evolution of land subsidence in the Beijing plain. Land subsidence during 2003–2014 in the Beijing plain was determined based on 39 ENVISAT Advanced Synthetic Aperture Radar (ASAR) images and 27 RadarSat-2 images. Results were consistent with global positioning system (GPS), leveling measurements at the point level and TerraSAR-X subsidence maps at the regional level. It was demonstrated that the land surface in the Beijing plain is settling at an accelerating rate. The average deformation rate in the line-of-sight (LOS) was from −124 mm/year to 7 mm/year during 2003–2014; accumulative displacement was up to 1426 mm by the end of 2014. To predict future subsidence, the evolution of deformation was used to build a prediction model based on an improved Grey-Markov model (IGMM), which adapted the conventional GM(1,1) model by utilizing rolling mechanism and integrating a k-means clustering method in Markov-chain state interval partitioning. Evaluation of the IGMM at three representative points showed good accuracy of simulated subsidence values (root-mean-square error <3 mm). Simulated deformation during 2013 and 2014 agreed well with the observed deformation during each year based on PS-InSAR (R2 = 0.94 and 0.91). Finally, InSAR measurements from 2003–2014 were used to predict subsidence in 2015–2016. It was calculated that the maximum cumulative deformation will reach 1717 mm by the end of 2016 in Beijing plain. The promising results indicate that this method provides an alternative to the conventional numerical and empirical models in order to predict short-term deformation when there is lack of detailed geological or hydraulic information.
2D and 3D Urbanization Change Detection Using PolSAR Data Sets
1Università di Pavia, Italy; 2Nanjing University
Change detection of urban extents is now a very important topic for urban remote sensing mapping at regional and global scales. Indeed, since more and more single-date and global data sets are becoming available, change detection of urban areas is feasible. However, so far it ahs been focused on binary changes, i.e. changes that affect (either positively or negatively) the urban area extents, by considering new urbanized areas or zones given back to the natural environment.
This work aims at providing a few preliminary results of a more accurate analysis, where the density of built-up areas, and the change from low-rise to high-rise buildings (and vice versa) is also considered. The rationale for this analysis is that these situation correspond to change that mostly go unnoticed when urban extents only are considered. Still, these changes are extremely important to understand phenomena related to change in population density, leading often to overcrowding effects, and subsequently to risk management issues.
To find a sound methodology and extract this more complex changes, we explore the use of SAR, and specifically polarimetric SAR, data, under the assumption that the electromagnetic field backscattered from built-up area is affected by the geometric properties of the illuminated structures, and therefore it is different according to the type of built-up elements located in a specific geographical area. Accordingly, a segmentation of the SAR image is first performed at the first date of thr temporal sequence to be analyzed, and then multiple polarimetric parameters (in addition to the backscattered intensity) are considered, to understand which are the parameters that are more useful to analyze to track not only 2D, but also 3D changes and density changes in urban areas.
The test area for this work is the city of Nanjing, and the data sets that were used are obtained from Radarsat-2 fully polarimetric images. A complete analysis of segmentation using different object size, applied to different polarimetric decomposition parameters, and validate using both positive and negative 2D and 3D changes in urban areas have been performed. They show that it is possible to extract a richer analysis for urban changes than the simple detection of changes in urban extents in a bi-dimensional sense. However, a clear and quantitative description of the 3D change is still to be obtained, and the methodology needs to be improved to reach this goal.
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