Bare Surface Soil Moisture Estimation Using Double-Angle and Dual-Polarization L-Band Radar Data

Based on today's most widely used surface scattering model, the advanced integral equation model (AIEM), this study proposes a novel soil moisture inversion model that estimates bare surface soil moisture using double-incidence angle and dual-polarized L-band radar data. Compared with previous studies at L-/C-band, the proposed method provides the estimation of soil moisture without referring to the measured soil roughness and eliminates the requirement of an initial dry season condition. The root-mean-square error (rmse) of volumetric soil moisture varies from 0.8% to 3.2% at different incidence-angle combinations validated by simulated solving and from 4.0% to 7.9% by field measurements when the paired incidence angles are not both large. In case the paired angels are both large, not particularly suitable for soil moisture estimation, the rmse increases to 10.3%. Therefore, this method is applicable to bare surface soil moisture retrieval when at least one of the incidence angles is not large.