Abstract: Based on the observation quality analyzing of daily soil relative humidity data in Yunnan from 2016 to 2020, 0−10cm CLDAS soil relative humidity data was introduced and its applicability was analyzed. The results showed that the observation efficiency of relative humidity data in Yunnan soil water observation station was not high, so it was necessary to use land surface fusion data to monitor agricultural drought. The absolute error between the relative humidity of nearly 80% of CLDAS soil in Yunnan region and the observed values of soil moisture observation stations is less than 30%, indicating high data reliability. In the central region of Yunnan, where drought occurs frequently, the correlation coefficient between the soil relative humidity of CLDAS and the observed values of soil moisture observation stations is above 0.8, and the average deviation is less than 10%. From the perspective of agricultural drought monitoring effectiveness, the drought monitoring index based on CLDAS soil relative humidity can well describe the changes in soil moisture caused by abnormal temperature and precipitation. When the daily rainfall is close to or exceeds 5.0mm, it can quickly respond to the decrease in the number of light drought stations; When continuous effective precipitation occurs, the monitoring index can reflect the relief of agricultural drought of medium and above grade. In summary, CLDAS soil relative humidity is suitable for agricultural drought monitoring in Yunnan province.

Key words: CLDAS, Soil relative moisture, Yunnan, Agricultural drought