Time series analysis of SMOS and ASCAT: Soil moisture product validation in the Rur and Erft catchments

ASCAT and SMOS soil moisture products were validated for the year 2010 in the Rur and Erft catchments in the west of Germany. In situ data of three test sites of the TERENO initiative were used to calibrate the hydrological model WaSiM-ETH, which was applied to generate a soil moisture reference for the whole study area. Comparison of SMOS soil moisture with the reference displayed a high dry bias and low to moderate correlations. ASCAT soil moisture showed higher correlations and no bias. A temporal stability analysis exhibits low stability of the SMOS data and higher stability of ASCAT data. Generally, the performance of ASCAT is well, while there are still some problems with soil moisture retrieval and RFI in the SMOS soil moisture product.