Evaluation of simulated soil moisture from China Land Data Assimilation System (CLDAS) land surface models

ABSTRACT

This study evaluated the land surface model-simulated soil moisture (SM) product from the China Land Data Assimilation System (CLDAS). This was achieved using three densely instrumented in situ observation networks in China that have different environmental conditions, i.e., the Hebi, Naqu and Heihe sites. The European Space Agency Climate Change Initiative multi-satellite-retrieved SM product (CCI-SM) was also included for inter-comparison purposes. Standard validation scores indicated that the CLDAS-SM product has high correlation and low uncertainty with both surface and root-zone soil moisture observations. The target accuracy (0.04 m³ m^?3) was achieved over all three sites. Compared with the CCI-SM product, the CLDAS-SM product showed higher accuracy for the Hebi and Heihe sites but slightly lower accuracy for the Naqu site located at the centre of the Tibetan Plateau. Regionally, the unbiased root mean square difference between the CLDAS-SM and CCI-SM products was noticeably smaller within China than in neighbouring countries. Given that the performance of the CCI-SM product should be unaffected by country boundaries, the better performance of the CLDAS-SM product in China can be attributed primarily to the high-quality meteorological forcing data.