Regularized Dual-Channel Algorithm for the Retrieval of Soil Moisture and Vegetation Optical Depth from SMAP Measurements

— In August 2020, SMAP released a new version of itssoil moisture (SM) and vegetation optical depth (VOD) retrievalproducts. In this work, we review the methodology followed by theSMAP regularized dual-channel (DCA) retrieval algorithm. Weshow that the new implementation generates SM retrievals thatnot only satisfy the SMAP accuracy requirements but also show aperformance comparable to the single-channel algorithm that usesthe V polarized brightness temperature (SCA-V). Due to a lack ofin situ measurements we cannot evaluate the accuracy of the VOD.In this work, we show analyses with the intention of providing anunderstanding of the VOD product. We compare the VOD resultswith those from SMOS. We also study the relation of the SMAPVOD with two vegetation parameters: tree height and biomass.