C-band radar for soil moisture estimation under agricultural conditions

A time series of space-borne ERS-2 SAR satellite data is used for the temporal monitoring of the soil moisture in Sukhothai area, Thailand. The backscattering coefficient σ⁰ from the SAR data has shown reasonable correlation and sensitivity to the observed volumetric soil moisture at 5 cm depth in Thailand at the field scale. A tandem coincidence of the ERS-2 and Radarsat missions, with two different polarizations, over the area provided an opportunity to estimate soil moisture over a large area by inverting a semi-empirical backscattering model. The estimates were validated with the field observations over a small area and are in good agreement. Furthermore, the soil moisture at a point was simulated using three hydrological models and compared with the radar backscattering and the point observations. There are large variations in the responses of these approaches.