Taking into account vegetation effects to estimate soil moisture from C-band radar measurements

Estimation of surface soil moisture is one of the major potential applications of radar remote sensing. The European Remote Sensing Satellites (ERS 1 and 2) are equipped with a Synthetic Aperture Radar working at C-Band (5 Ghz) using a rather low incidence angle (23°). For this frequency and angle, the effect of soil roughness and vegetation attenuation are not negligible. Therefore, it is difficult to estimate the surface soil moisture using an algorithm that could be valid for the entire year. In this article it is shown, that, for wheat canopy, it is possible to apply an empirical relation for correcting for the effect of vegetation. The proposed algorithm is derived from a data set acquired over several years (from 1988 to 1994) using an airborne- radar. It uses a simple cloud model to describe the vegetation attenuation. This algorithm does not need very precise information on vegetation density and yields a final precision for the moisture content on the order of 0.05 cm3/cm3.