Recent advances in microwave sensing of soil moisture

A new approach for retrieving surface soil moisture from satellite microwave brightness temperature is described. The approach uses radiative transfer theory together with a non- linear optimization routine to partition the observed microwave signal into its soil and vegetation components. Vegetation optical depth is derived directly from the microwave polarization difference index, while the soil component is solved in terms of the soil dielectric constant. A global data base of soil physical properties is then used to derive soil moisture from the soil dielectric constant. The approach is tested with historical SMMR data to produce time series of surface soil moisture over several global test sites. Comparisons with ground observations of soil moisture are made. Preliminary results over several global test sites are provided.