Soil moisture estimation using multi-incidence and multi-polarization ASAR data

The potential of Advanced Synthetic Aperture Radar (ASAR) for the retrieval of surface soil moisture over bare soils was evaluated for several ASAR acquisition configurations: (1) one date/single channel (one incidence and one polarization); (2) one date/two channels (one incidence and two polarizations); (3) two dates/ two channels (two incidences and one polarization); and (4) two dates/four channels (two incidences and two polarizations). The retrieval of soil moisture from backscattering measurements is discussed, using empirical inversion approaches. When compared with the results obtained with a single polarization (HH or HV), the use of two polarizations (HH and HV) does not enable a significant improvement in estimating soil moisture. For the best estimates of soil moisture, ASAR data should be acquired at both low and high incidence angles. ASAR proves to be a good remote sensing tool for measuring surface soil moisture, with accuracy for the retrieved soil moisture that can reach 3.5% (RMSE).