Verification of Patch- and Regional-Scale Energy Balance Estimates Derived from Microwave and Optical Remote Sensing during SGP97

Abstract

The 1997 Southern Great Plains Hydrology Experiment (SGP97) was designed and conducted to extend surface soil moisture retrieval algorithms based on passive microwave observations to coarser resolutions, larger regions with more diverse conditions, and longer time periods. The L-band Electronically Scanned Thinned Array Radiometer (ESTAR) on an airborne platform was used for daily mapping of surface soil moisture over an area of approximately 40 km ? 260 km for a 1-month period. Results showed that the soil moisture retrieval algorithm performed the same as in previous investigations, demonstrating consistency of both the retrieval and the instrument. This soil moisture product at 800-m pixel resolution together with land use and fractional vegetation cover information is used in a remote sensing model for computing spatially distributed fluxes over the SGP97 domain. Validation of the model output is performed at the patch scale using tower-based measurements and at regional scale using aircraft flux observations. Comparisons at the patch scale yielded discrepancies between model- and tower-based sensible and latent heat fluxes of 40% and 20%, respectively. At regional scales, differences between modeled and aircraft-based sensible and latent heat fluxes were less, on the order of 30% and 15%, respectively. A preliminary comparison of regional average energy fluxes with a model using remotely sensed temperatures was conducted and yielded good agreement. The utility of spatially distributed energy flux and model-simulated surface temperature maps over the SGP97 region is discussed.