Abstract: Based on the daily observation data of automatic soil moisture stations in Liaoning province during growing season (May to October) in 2020, the simulation performance of CLDAS(CMA Land Data Assimilation System) relative soil moisture products at 0−10cm, 0-20cm and 0-50cm levels was evaluated and tested by using statistical evaluation indices and methods including correlation coefficient (r), root mean squared error (RMSE), mean absolute error (MAE) and deviation to comprehend the application of CLDAS fusion relative soil moisture data. The results showed that there are trend consistency and significant positive correlation on time scale between CLDAS relative soil moisture simulation results and observed values in three soil layers. During the growing season, the simulation results of CLDAS average relative soil moisture were generally high. CLDAS had a relatively nice simulation effect when the relative soil moisture was between 60% and 90%, and had a relatively poor simulation effect when the relative soil moisture data were in the state of partial wet (RSM > 90%) and partial dry (RSM < 60%). On the other hand, the spatial variation showed a consistent tendency between CLDAS relative soil moisture simulation results and observed values at three levels, and the overall distribution was relatively low in the west and relatively high in the east. There was a significant positive correlation between CLDAS relative soil moisture simulation results and observed values, and the correlation coefficient was more than 0.8 in 0-20cm and 0-50cm soil layer in most areas of Liaoning province. The distribution trend of error assessment results was coincident in the whole province. The errors in the eastern, southern and western parts of Liaoning were relatively small, while those in the northern and central parts were relatively large. Abnormal high value area of error occurred in the line of Kangping-Zhangwu-Xinmin-Tai 'an. The relative soil moisture simulation results of CLDAS had a fairly strong applicability and stability in Liaoning province, which could reflect the variation of soil water surplus and deficit well.

Key words: CLDAS, Relative soil moisture, Liaoning province, Evaluation and verification