The summertime climate of the central United States is characterized by high spatial variability in precipitation, resulting in high spatial variability in soil moisture and crop stress. Monitoring these conditions and identifying areas of potential crop damage from deficient or excessive soil moisture can be problematic because the existing network of precipitation observations is not of sufficient spatial resolution to identify small-scale variations in precipitation. The Midwestern Climate Center has been simulating soil moisture conditions for the purposes of real-time monitoring since 1989 using a model that runs at the resolution of the crop reporting district. There are a number of applications where higher resolution is required. Because of the aforementioned characteristics of the climate, the CRD estimates are not always of sufficient accuracy for these higher resolution applications.
The existing soil moisture modeling system has been modified so that soil moisture estimates can be made at the resolution of a county. County resolution soil characteristics were derived using the STATSGO soils data base of USDA's Natural Resources Conservation Service. Higher resolution precipitation estimates in real-time are being obtained from the National Weather Service's NEXRAD radar system at a 15 km resolution. While this provides the necessary spatial resolution, the accuracy of the rainfall estimates is limited by the well- known uncertainties in the radar signal-rainfall relationship.
This paper will describe the results of an analysis of high resolution soil moisture estimates for the summers of 1997 and 1998. In particular, the sensitivity of the soil moisture estimates to uncertainties in the radar rainfall estimates will be quantified.