Overview and details of the sessions and sub-session of this conference. Please select a date or session to show only sub-sessions at that day or location. Please select a single sub-session for detailed view (with abstracts and downloads if available).
C3: ID.10680 Hydrology Products
Ecological condition and water resource assessment for the China-ASEAN area based on the Multi-source remote sensing observations
Institute of Remote Sensing and Digital Earth, China, People's Republic of;
Multi-source Synergized Quantitative Remote Sensing Production System (MuSyQ) has been developed in order to fully integrate the Chinese, European, and other satellite observation to retrieve the global and regional scale land surface parameters, which are very important for the study of regional water cycle to support water resources management. Preprocessing and normalization processing have formed standard multi-source remote sensing datasets, and further produced remote sensing products including surface reflectance, land surface temperature, Albedo, Photosynthetically Active Radiation (PAR), land surface evapotranspiration, vegetation index, vegetation coverage, length of vegetation growing season, Net Primary Productivity (NPP), forest biomass and so forth. ASEAN (Southeast Asia) mainly includes the Indo-China Peninsula and Malay Archipelago in the southeast of Asia, which consists of Cambodia, Laos, Myanmar, Thailand, Vietnam, Singapore, Malaysia, Brunei, Indonesia, and Philippines. Large-scale monitoring and analysis have been conducted for vegetation and water conditions of the China-ASEAN area in 2013 and 2014. The land surface parameter products are used to simulate the water resources in the Lancang-Mekong River Basin. Comprehensive assessment has been tried based on the ecological environmental and water resource conditions for the China-Asian area.
Terrestrial Water Cycle in South and East Asia: Hydrospheric and Cryospheric Data Products
1Faculty of Civil Engineering and Earth Sciences, Delft University of Technology, Post Box 5048, 2628 CN Delft, The Netherlands; 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;
The South and East Asia is characterized by a significant intra-annual variability and spatial heterogeneity of surface conditions. Snow and vegetation cover, albedo, land surface temperature and wetness change very significantly during the year and from place to place. The state of the land surface over the entire region can be determined by space observation. Fully integrated use of satellite and ground observations is necessary for the study of regional water cycle to support water resources management in South and East Asia, and to clarify the roles of the interactions between the land surface and the atmosphere over the region in the Asian monsoon system.
The state of the land surface and the water cycle over the South and East Asia can be determined by space observation. New or significantly improved algorithms have been developed and evaluated against ground measurements. Variables retrieved include land surface properties, i.e. NDVI, LAI, FPAR, albedo, soil moisture, glacier and lake levels. Based on these biophysical parameters derived from microwave and optical remote sensing observations, a hybrid remotely sensed evapotranspiration (ET) estimation model named ETMonitor was developed and applied to estimate the daily actual ET of the Southeast Asia at a spatial resolution of 1 km. The changes in glaciers and lakes on the Tibetan Plateau, and the drainage links between glaciers and lakes are determined in this climate-sensitive region
Global Terrestrial Evapotranspiration from Optical and Microwave Satellite Observations
1State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China, People's Republic of; 2Delft University of Technology, Delft, The Netherlands;
Terrestrial actual evapotranspiration (ET) includes evaporation from soil and waterbodies, evaporation of intercepted rainfall by the vegetation canopy, transpiration from leaves and sublimation of snow and ice. It is a crucial process at the land surface that connects energy, water and carbon cycles over the land surface. Many efforts in the past decades have focused on developing methods and various regional applications by using land surface biophysical parameters derived from optical satellite observations. Interest in the last decade has moved to producing ET products in a continuous and quasi-operational manner due to the strong need from many sectors including studies for global environment and climate change, water consumption and water accounting, water resource allocation, drought monitoring and mitigation, etc.
A hybrid remotely sensed ET estimation model named ETMonitor was developed to estimate the daily actual ET globally considering the diverse landscapes and multi-climatic features. The ETMonitor model integrates the description of land surface energy balance, water balance (soil water movement) and vegetation physiological process, which utilizes the land surface biophysical parameters observed using measurements from optical to microwave spectral domain. One essential issue is the parameterization of the soil moisture deficit modulating the surface resistances. The surface soil moisture at fine spatial scale was downscaled from the microwave satellite observations by the “Universal Triangle” method using NDVI, LST, and albedo. The downscaled soil moisture was assimilated into the ETMonitor model using EnKF to improve the soil moisture prediction and reduce the uncertainty of simulated ET. Both current existing products of land surface parameters and those derived within the project by using multi-source remote sensing observations made by Chinese, European and USA satellites are taken as input to produce global evapotranspiration for all sky conditions. The results were evaluated against eddy covariance measurements at sites in China and Europe, intercompared with other ET data sets based on satellite retrievals, and some preliminary applications were conducted for regional- to global-scale mapping and monitoring of water consumption and drought severity.
Evaluation of a 3-years time-serie of daily actual evapotranspiration over the Tibetan Plateau
1ICube Laboratory, University of Strasbourg, France; 2Faculty of Civil Engineering and Geosciences, TU Delft, The Netherlands;
The estimation of turbulent fluxes is of primary interest for hydrological and climatological studies. Also the use of optical remote sensing data in the VNIR and TIR domain already proved to allow for the parameterization of surface energy balance, leading to many algorithms.
In the perspective of large scale and long-term studies for the monitoring of land surface evapotranspiration, SEBS algorithm was adapted for dealing with the multiple scales of input data, in respect with the representative scale of the involved physical processes. The Multi-Scale Surface Energy Balance System (MSSEBS) principle has been implemented into SEBS, and applied to an area of 2.5 million square kilometers including the Tibetan Plateau and the headwaters of the major rivers of eastern and southern Asia. The combination of continuous LST gap-filled observations with advanced land surface parameters and atmospheric fields, allowed to compute a 3-years time-series (2008-2010) of instantaneous land surface turbulent heat fluxes at a daily frequency.
Two methods for the scaling of daily evapotranspiration (ETd) were evaluated in order to retrieve the most accurate daily rate from the extrapolation of one estimation over the diurnal period. Results have been then evaluated against heat flux measurements provided by Eddy Covariance systems at four locations over the Tibetan Plateau. The scaling method for a daily integration based on a sine function, clearly showed a better agreement with ground measurements. However, during the monsoon season, the integration of hourly heat flux calculations gave much better results, by taking into account the daily pattern of net radiation affected by cloud coverage. Moreover, following the characterization of the surface roughness into the model, the estimation of heat fluxes for hilly areas can slightly vary. Finally, MSSEBS is much more sensitive to the difference of atmospheric fields provided as an input. For some locations, RMSE in the estimation of ETd can be up to two times greater following the atmospheric data chosen.
Generation of a 3-years time-serie of daily actual evapotranspiration over the Tibetan Plateau
1ICube Laboratory, University of Strasbourg, France; 2Faculty of Civil Engineering and Geosciences, TU Delft, The Netherlands;
The estimation of turbulent heat fluxes is of primary interest for hydrological and climatological studies. Also the use of optical remote sensing data in the VNIR and TIR domain already proved to allow for the parameterization of surface energy balance, leading to many algorithms. Their use over arid and high-elevated areas require detailed characterization of key surface physical properties and atmospheric statement at a reference level. Satellite products aquired over the Tibetan Plateau and simulations results delivered in the frame of the CEOP-AEGIS project provide incentives for a regular analysis at medium scale.
This study aims at integrating spaceborne optical remote sensing data, such as Feng-Yun 2 series or MODIS (VNIR and TIR) for actual evapotranspiration (ET) mapping over the whole Tibetan Plateau, and based on the SEBS algorithm. Hence, the Multi-Scale Surface Energy Balance System (MSSEBS) principle has been implemented into SEBS, and applied to an area of 2.5 million square kilometers including the Tibetan Plateau and the headwaters of the major rivers of eastern and southern Asia. The combination of continuous LST gap-filled observations with advanced land surface parameters and atmospheric fields, allowed to compute a 3-years time-serie (2008-2010) of actual ET at a daily frequency and 1km sampling resolution over the entire Tibetan Plateau. The complete dataset of daily evapotranspiration (2008-2010) has been used in the frame of the CEOP-AEGIS project as an input for the distributed water balance mode.
Merging Multiple Microwave Radiometer Data to Monitor Daily Water Saturated Surface
Delft University of Technology, The Netherlands;
Water saturated surface (WSS), i.e. water saturated soil and inundated area, is a key factor to model the partition of precipitation at the land surface. WSS can be retrieved from data acquired by microwave radiometers around 37GHz, such as SSM/I and AMSR-E. With a single radiometer, frequent observation gaps lead to large amount of lost information on surface changes. Merging data from SSM/I and AMSR-E and eventually other similar radiometers, is thus necessary, while the differences in IFOV, viewing angle and observation time lead to additional difficulties to achieve inter-sensor calibration. Consistent observations of surface changes were obtained by modelling the time series using a Fourier series. The influence of differences in the viewing angle and observation time is assumed to be aperiodic or to yield noises at high frequencies. The frequency pattern of the atmospheric influence on surface observations was determined through auxiliary data. The noisy components can be removed in the frequency domain and residuals are assumed to represent consistent surface changes. The amplitudes of remaining frequencies are then used to calibrate brightness temperature measured by AMSR-E to that by SSM/I. The new daily observations of WSS are then retrieved from the merging time series of the two radiometers.
An operational method to estimate daily solar radiation budget at the square kilometre over the Tibetan Plateau from MODIS data products integrating spatial and temporal heterogeneity
1ICube Laboratory, UMR 7357 CNRS-University of Strasbourg, 300 bd Sébastien Brant, CS 10413, F-67412 Illkirch Cedex, France; 2State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, P.R. China; 3Faculty of Civil Engineering and Earth Sciences, Delft University of Technology, Post Box 5048, 2628 CN Delft, The Netherlands;
In the current context of climate change, an estimation of surface radiation fluxes at fine spatial and temporal resolution is fundamental to understand and model convective exchanges in the troposphere and their evolution. This requires the quantification of the physical processes happening at the surface-atmosphere interface and the definition of hydro-climatic indicators to characterise the soil water status and by extension to predict drought events. Considering large and complex areas like the Tibetan Plateau, an analysis of the spatial distribution of the solar radiative budget over time not only requires the use of satellite remote sensing data, but also of an algorithm that properly accounts for strong variations of topography. Therefore, this research aims at developing an operational method to produce time series of solar radiative fluxes at high temporal and spatial resolution based on observed surface and atmosphere properties as well as topography. As compared to other existing solar radiation products, the challenge is to model the solar radiation budget at a higher spatial resolution and to properly account for the variations in topography. With the current spaceborn sensors available, a daily monitoring of the surface radiative fluxes limits the spatial resolution to the square kilometre. Some satellite data products have been developed and regularly improved to characterize the atmospheric and land surface properties at these spatial and temporal scales. The idea is then to assess the accuracy that can be achieved by using those existing satellite data products to estimate solar radiative fluxes over heterogeneous areas daily and at the square kilometre. To do so, MODIS satellite data products time series and the ASTERGDEM digital elevation model (DEM) are used. The proposed method combines the different MODIS products to account for the atmospheric and surface albedo variations and uses the mean terrain slope and azimuth of each square kilometre pixel derived from the DEM to calculate the irradiance according to the local illumination angle. The algorithm provides instantaneous fluxes computed for all skies conditions which are then aggregated into daily averages. The developed approach led to the production of a three-year time series (2008-2010) of instantaneous and daily solar radiative fluxes at the square kilometre across the Tibetan Plateau. The validation showed that, even if the solar radiation estimates are satisfying under clear sky conditions, the algorithm is less reliable under cloud cover and the albedo product used here has a too coarse temporal resolution and is not accurate enough over rugged terrain. In the light of those conclusions, further research were performed to improve physical processes modelling like the estimate of surface irradiance and albedo in extreme topographic conditions and also to refine the temporal resolution of the albedo using geostationary satellite observations (FengYun 2E). The improved parameters have been used to recompute the solar radiation budget for a small test sites in order to evaluate the improvements brought the developed method.
Monitoring Changes In Glacial Thickness And Lake Level On The Tibetan Plateau Exploiting The ICESat Laser Altimeter
1Hochiminh City University of Technology, Vietnam; 2Delft University of Technology;
The Tibetan Plateau has the largest glacier-covered area outside the Poles, containing ~37,000 glaciers that together occupy an area of ~56,560 km2. There are thousands of lakes on this region, ~900 lakes of which have an area of over 1 km2. In general, glacial melt water from mountains feeds lakes and rivers on the Tibetan Plateau. Moreover, changes in water storage of open water bodies can be assessed by analysing changes in their water levels. Therefore, estimating the water storage change of the Tibetan Plateau requires estimating changes in glacial thickness and lake level. As an alternative to other remote sensing techniques, satellite laser altimetry is a potential solution to assess hydrologic processes in this region. In this study, we observe changes in glacial thickness and lake level on the Tibetan Plateau integrating the ICESat laser altimetry data and other data products derived from remotely sensed data and then recognize obviously their relationship.
Because of its orbit constellation, ICESat only sparsely sampled glaciers and lakes on the Tibetan Plateau were observed between 2003 and 2009. Firstly, trends in the estimated thickness of 90 glacial areas on the whole Tibetan Plateau were estimated by exploiting ICESat GLA14 land surface elevation data in combination with the SRTM DEM and the GLIMS glacier mask. Then, water level variations of 154 lakes spread all over the Tibetan Plateau could be obtained by using the ICESat GLA14 land surface elevation data in combination with the MODIS land-water mask. Finally, geometric links between glaciers and lakes on the Tibetan Plateau were determined by applying a surface flow network analysis in catchments with both a lake and a glacier. The surface flow network was based on the HydroSHEDS product which was derived from the SRTM digital elevation model data. The results indicated that 25.3% of the glaciers release their melt water directly to 244 lakes. In general, the geometric dependency of Tibetan lakes on glacial runoff presented a simple representation of a potential relationship between changes in glacier thickness and lake levels. Moreover, the current results on glacial and lake level changes are expected to contribute the understanding of the hydrologic processes and the input data of the water balance model of the Tibetan Plateau.
Contact and Legal Notice · Contact Address:
Conference: 2016 Dragon 3 Final Results Symposium
|Conference Software -
ConfTool Pro 2.6.94
© 2001 - 2016 by H. Weinreich, Hamburg, Germany