Soil moisture inversion from ERS and SIR-C imagery at the Zwalm catchment, Belgium

Several models have been presented in the recent past which should allow soil moisture inversion from bare soil radar backscattering. Three widely used models (i.e. the IEM, the models of Dubois et al. and of Oh et al.) have been applied to ERS and SIR-C data obtained over the Zwalm catchment in Belgium. Results show an inability of the models to estimate surface soil moisture accurately through direct inversion. However, applying the method of effective roughness parameters on the multi-temporal ERS tandem mission data resulted in a significant improvement of the soil moisture retrieval. The same method applied to multi-frequency SIR-C data was not able to improve the estimations. It is believed that the inversions suffer from the high soil roughness sensitivity of the backscattering at higher incidence angles.