InterComparison and Evaluation of MultiSource Soil Moisture Products in China

Long-term, accurate soil moisture (SM) estimates are crucial for climate, hydrology, and agriculture. Multisource SM products are available at high spatiotemporal coverage, but their uncertainties have yet to be fully evaluated in China. Ten SM products (i.e., reanalysis, assimilation, and satellite) were intercompared and evaluated over 18 hydroclimatic regions of China during 2000-2018 at different scales. The results show that all SM products share similar spatial patterns but exhibit significant differences in regions and products. The interannual fluctuations and differences between these products are relatively small, except for the anomalies of ESA CCI ACTIVE and PASSIVE in southern China. At a seasonal scale, the estimates of NCEP R2, ACTIVE, and PASSIVE for specific regions are significantly different from other products. Moreover, all SM products correlate well with precipitation in summer and have their own dominant areas. Among them, ERA5 shows a comprehensive potential for application in China. The temporal correlation coefficient (R), root mean square difference (RMSD), and standard deviation (sigma) demonstrate that ERA5 performs better in southern China, while CLSM performs better in the northeast and throughout China, with R exceeding 0.7 for both products. For the Equitable Threat Score (ETS), ERA5 has a better overall performance with scores greater than 0.03 distributed in more regions of China, followed by ACTIVE and CFSR/CFSV2. This study not only provides a reasonable reference for the targeted selection of SM products in different hydroclimatic regions of China but also establishes a preliminary data basis for the integration of multiple products.