Polarimetric SAR decompositions for soil moisture retrieval over corn fields in Argentina

In this study, we investigate the synergic use of polarimetric Synthetic Aperture Radar (SAR) decompositions and electromagnetic models for soil moisture retrieval over corn fields. The Generalized Freeman-Durden decomposition (GFD) is applied to a time-series of L-band full-polarimetric SAOCOM-1A data collected during the 2019-2020 growing season over an agricultural area. The scattering mechanisms (i.e., surface, double-bounce, and volume) derived from the decomposition are compared with the ones simulated using the Tor Vergata electromagnetic model. The goal of the work is to evaluate the capabilities of the GFD to consistently assign each scattered power to the corresponding scattering mechanism, so that the sensitivity to soil moisture and vegetation can be highlighted. Results point out significative discrepancies, especially for the volume term, while a good agreement is found for the double-bounce contribution. Differences are further confirmed when a simple linear regression model is applied to retrieve soil moisture using the GFD scattered powers or the model powers.