A FRAMEWORK FOR RETRIEVING A TIME-VARYING EFFECTIVE SCATTERING ALBEDO FROM SATELLITE MICROWAVE MEASUREMENTS

Current satellite soil moisture retrieval algorithms require estimation techniques or a priori information about microwave vegetation properties, specifically the vegetation optical depth and single scattering albedo. Most approaches assume a constant single scattering albedo (w), a function of canopy architecture and orientation, despite few investigations of this property. Here, dynamic w is retrieved over cropland and natural landscape pixels with Soil Moisture Active Passive (SMAP) brightness temperature measurements within the multi-temporal dual-channel algorithm using a moving window retrieval approach. A longer moving window length (number of overpasses with w constant) is recommended to ensure adequate degrees of information for retrieval and to prevent spurious, rapid changes in w. It was determined that the mean and standard deviation of both soil moisture and vegetation optical depth are reduced with increased w. w also interestingly decreased during the vegetation growth phase suggesting it may be an effective parameter absorbing other physics not accounted for in the zeroth-order radiative transfer equation.