Microwave soil moisture prediction through corn in Washita '92

During June, 1992 NASA and USDA conducted a hydrology field experiment 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. As part of this experiment, truck radar data at 1.6 GHz acquired over a large corn field were used to validate the performance of a vegetation model in which discrete scatter random media techniques are employed to calculate vegetation transmissivity and scattering. These parameters were then used in a soil moisture prediction algorithm utilizing aircraft microwave data from the 1.4 GHz ESTAR radiometer. Over the 8 flight days of the experiment (during which soil moisture decreased over 20% from the saturated conditions at the start), the match of predicted to measured soil moisture was excellent, with an average absolute error of less than 1.5%. For the corn, canopy encountered in Washita '92 (2.1 m tall with canopy water content of 4.05 kg/m/sup 2/), the inclusion of the small single scattering albedo in the algorithm slightly improved the prediction of soil moisture.<
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