Surface Soil Moisture Retrieval Over Irrigated Wheat Crops in Semi-Arid Areas using Sentinel-1 Data

The sensitivity of the backscattering coefficient and the interferometric coherence to surface soil moisture changes and wheat crops growth was analyzed using the time series derived from C-band Sentinel-1. Results show that the interferometric coherence is sensitive to wheat biomass while the backscatter intensity is more influenced by the surface soil moisture (SSM) changes. A new method to retrieve SSM combining the interferometric coherence and C-band backscattering coefficient acquired by Sentinel-1 is tested over two irrigated wheat plots during two growth seasons around Marrakech city (center of Morocco). It is shown that SSM can be estimated with a reasonable accuracy from sowing to harvest $(R=0.65$; RMSE $=0.07 m^{3}/ m^{3}$; bias $=0.01 m^{3}/ m^{3})$. These results enhance the potentialities of Sentinel1 data for SSM retrieval even in the presence of a dense canopy.