Investigation of the accuracy of soil moisture inversion using microwave data and its impact on watershed hydrological modeling

During 1992 and 1994 NASA/GSFC, USDA, and Princeton University conducted hydrology field experiments in the Little Washita River watershed near Chickasha, Oklahoma, with a goal of characterizing the spatial and temporal variability of soil moisture using microwave sensors from ground, aircraft, and space platforms. A major objective of these activities included the subsequent incorporation of the microwave-derived soil moisture patterns in models of larger scale water balance and partial area hydrology. While work is continuing to improve the accuracy of microwave soil moisture inversion algorithms for both bare and vegetated soils, the impact of errors in estimated soil moisture on hydrological modeling of the watershed has yet to be addressed. In this study a coupled water and energy balance model operating within a topographic framework was used to predict surface soil moisture fields for the Little Washita watershed for an eight-day period in June, 1992 which covered a wide range of soil moisture conditions. The model was first driven by meteorological forcing data, and the model-generated soil moisture fields are compared in space and time to those produced for the watershed by the airborne passive microwave ESTAR sensor for the same time period. In a second analysis, the model was initialized by the remote sensing data, and subsequent model predictions of soil moisture are compared to measured values.