Evaluation of empirical and semi-empirical backscattering models for surface soil moisture estimation

Several empirical and semi-empirical backscattering models have been proposed to offer alternative expressions for the inversion of surface parameters from radar data, but the applicability and adequacy of the models for different surface conditions and sensor configurations have not been clearly assessed. A number of empirical and semi-empirical models are studied in this paper to assess the applicability of the models for different conditions that are often found over agricultural areas. The performance of the models is evaluated first analytically by comparing their simulations with those obtained using the theoretical integral equation model (IEM) and geometrical optics model (GOM). The model estimations are then compared with RADARSAT-1 observations acquired over an experimental catchment. The results show very different model behaviour depending on the surfaces roughness conditions and incidence angle. This study highlights the importance of carefully selecting the backscattering model to be used in radar applications.