A model-based determination of soil moisture trends in Spain with the ERS-scatterometer

The ERS-1 Wind Scatterometer (WSC) has a resolution cell of about 50 km but provides a high repetition rate (<4 days) and makes measurements at multiple incidence angles. In this study, a mixed target modeling approach is applied to WSC data to estimate effective surface reflectivity (related to soil moisture content) at four test locations in Spain. The model represents the footprint area as a combination of part dense, homogeneous vegetation, and part bare soil (with homogeneous roughness and dielectric properties). The method is applied to WSC data over the period 1992-95, and results are compared to measurements of total monthly precipitation. The results illustrate the applicability of WSC data for measuring soil moisture content-related parameters and offers a physically-based alternative to empirical methods for monitoring trends in surface soil moisture content