Comprehensive evaluation of satellite-based and reanalysis soil moisture products using in situ observations over China

Abstract. Soil moisture (SM) plays a critical role in the water and energy cycles of Earth system; consequently, long-term SM product with high quality is urgently needed. In this study, five products, including one microwave remote sensing – European Space Agency's Climate Change Initiative (ESA CCI) four reanalysis data sets Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Interim (ERA-Interim), National Centers Environmental Prediction (NCEP), 20th Century Project from Oceanic Atmospheric Administration (NOAA), ECMWF 5 (ERA5) are systematically evaluated using situ measurements during 1981–2013 climate regions at different timescales over Chinese mainland. The results show that ESA CCI closest to observations terms both spatial distributions magnitude monthly SM. All products tend overestimate soil all but have higher correlations than except Northwest China. largest inconsistency found southern Northeast China region, an unbiased root mean square error (ubRMSE) value larger 0.04. However, exhibit certain weaknesses representing interannual variation relative bias 144.4 % ERA-Interim under extreme severe wet conditions northeastern China, lowest product, minimum 0.48 northwestern Decomposing errors suggests dominant contribution correlation term large CCI. As result, good option hydrometeorological applications on ERA5 also promising especially northern low coefficient. This intercomparison study provides clues enhancement further hydrological applications.