Empirical model for surface soil moisture estimation over wheat fields using C-band polarimetric SAR

This study proposes a simple empirical model based on polarimetric parameters extracted from RADARSAT-2 imagery to retrieve surface soil moisture (0-5 cm) over agricultural fields. The model is calibrated with ground data acquired from 13 wheat fields, over their whole growth cycle, during the SMAPVEX12 campaign. Sensitivity analysis of the extracted polarimetric variables to soil moisture demonstrated distinct correlations before and after the beginning of the crops flowering stage. Linear backscattering showed significant correlations for all polarizations before crops flowering. The empirical model based on combined linear backscattering coefficients and polarimetric variables allowed to retrieve soil moisture with a 0.076 m3/m3. RMSE if calibrated for the whole growth cycle, 0.067 m3/m3. RMSE if calibrated for data before crop flowering and 0.042 m3/m3. With the data after flowering.