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Downscaling advanced microwave scanning radiometer (AMSR-E) soil moisture retrievals using a multiple time-scale exponential rainfall adjustment technique
  • Published Date:
    2015
  • Source:
    J. Geophys. Remote Sens., 4(1), 1-15.
Filetype[PDF-1.96 MB]


Details:
  • Description:
    Hydrologic response at all resolutions is controlled by physical processes. Accurately capturing the physical process

    at a high-resolution is essential for down scaling many satellite observations at coarse resolutions. In this paper, a

    four-dimensional process representative soil moisture downscaling model is developed to downscale the Advanced

    Microwave Scanning Radiometer-EOS (AMSR-E) 25 km resolution soil moisture product. The model is composed of

    the calculation of an antecedent precipitation accumulation (APA) index to capture soil moisture spatial and temporal

    variations at the 500 m resolution, and the application of a Geographic Information System (GIS) to simulate physical

    processes which can regulate soil moisture changes throughout the watersheds. APA index, as a representation of

    the provisional value of soil moisture, is calculated by adopting an exponential formulation to synthesize the effects of

    infiltration, soil evaporative efficiency, and vegetation resistance on soil water content following precipitation. Five days

    of AMSR-E soil moisture derivatives spanning the start of the monsoon and the duration of the storm are selected for

    downscaling. The results show that soil moisture spatial variation is primarily controlled by the distribution of precipitation

    and soil properties. Subsequently relative soil moisture, radiation, and vegetation become significant in controlling landsurface

    fluxes and thus influence soil moisture variation as time progresses. The downscaled soil moisture data (500

    m resolution) are assessed using in-situ soil moisture measurements from the National Oceanic and Atmospheric

    Administration (NOAA) Hydrometeorology Testbed (HMT) and the U.S. Department of Agriculture (USDA) Southwest

    Watershed Research Center (SWRC) Walnut Gulch Experimental Watershed (WGEW) observing networks. The root

    mean square error (RMSE) between the disaggregated and in-situ soil moisture is 0.034 vol./vol. with percent bias

    (PBIAS) 0.85%. The overall R2 value is 0.788.

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