Estimating Spatial Disturbution of Surface Soil Mositure Conditions Using a Downscale Technique with Thermal Inertia Retrieved from AMSR2 Soil Moisture Products

Abstract:

We examined that a method for estimating spatial distribution of surface soil moisture conditions with a fine grid scale. The AMSR2 soil moisture products which have been produced by Japan Aerospace Exploration Agency (JAXA) with a coarse grid scale (50 km) were downscaled by a spatial distribution of thermal inertia (3 km), which was retrived from a two-source linear surface heat budget model using an optimization method in which the input variables such as MODIS surface temperature, insolation retrieved from a geostationary satellite, and surface meterological data were incorporated. The downscale technique employed a characteristic that thermal inertia is almost proportional to volumetric soil moisture content, which was found in results of some field experiments. This downscale technique was applied to the AMSR2 products of summer season of central Mongolia where typical and dry steppe were dominated. A preliminary result of the downscaling technique showed fairly good result that the values of downscaled soil moisture were varied in response to rainfall events at some grids where meteorological stations existed, while the values of AMSR2 were not significantly changed.