Soil Moisture Retrieval Only Using Smap L-Band Radar Observations

A soil moisture retrieval algorithm using L-band radar-only observations is applied to soil moisture active and passive (SMAP) radar observations. This algorithm is based on a nonlinear relationship between L-band backscatter and soil moisture, and any ancillary vegetation or roughness information is not needed. This algorithm is based on three limiting cases and end-members: smooth bare soil, rough bare soil and maximum vegetation covered soil. Those parameters is estimated through a iterative process. Three months global soil moisture is retrieved using SMAP radar observations and this algorithm. The accuracy of soil moisture result is validated by the ground network insitu observations and the SMAP standard radar and radiometer product. The soil moisture has similar spatial pattern with that of SMAP standard product at 9 km resolution. In the future, we can estimate the soil moisture at 3 km with SMAP radar data only.