Parameterized exponentially correlated surface emission model for L-band passive microwave soil moisture retrieval

Soil Moisture and Ocean Salinity (SMOS) satellite observations offer a unique resource for near-surface soil moisture retrievals. It could provide multi-angular microwave emission signals at L-band and thus provide an entree to infer soil moisture and roughness for bare soil. In this study, a simple model for simulating the L-band microwave emission from exponentially correlated surface was developed and implemented into soil moisture retrieval algorithm. The approach was based on the parameterization of an effective roughness parameter in relation with surface roughness variables (root mean square height and correlation length) and incidence angle. The parameterization was developed on a large set of simulations by a physical model of the advanced integral equation model (AIEM) over a wide range of geophysical properties. This methodology was then implemented using SMOSREX observations to estimate both soil roughness and surface soil moisture content. Results indicated the model developed in this paper can be very useful in understanding the effects of surface roughness on microwave emission and soil moisture retrieval algorithms from L-band passive microwave observations.