A Method to Assess the Performance of SAR-Derived Surface Soil Moisture Products

Synthetic aperture radar (SAR) is a remote sensing technique for mapping of soil moisture with high spatial resolution. C-band SAR can resolve features at field scale, or better, but responds to only within the top 1 2 cm soil. When validating SAR-derived products against standard in situ measurements 5 10 depth, greater variability surface may be inaccurately categorized as measurement error. An alternative method was developed where product validated simulated depth by HYDRUS-1D model. This reproduces profiles from daily meteorological observations, leaf area index, and hydraulic parameters. The model fitted 13 COSMOS-UK sites so that output closely reproduced cosmic ray neutron sensor data. At ten studied, there an improvement up 8% root-mean-squared difference Copernicus (SSM) compared cm. suggests SSM other algorithms more accurate than have hitherto been acknowledged.