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• Increased frequency and prolonged duration lead to rise in drought severity. • The eastern part of Yunnan Province was most sensitive to drought. • The southwestern part of Yunnan Province was vulnerable to long drought. • A significant increase in drought severity in the last decade. • Regional SM changes cannot be only attributed to "dry to dryer, wet to wetter" Droughts in humid regions may have more severe consequences owing to a lack of drought-resistant measures and awareness. The Yunnan Province, in the humid southwestern part of China, experienced an extreme drought from 2009 to 2010. However, few studies have systematically explored agricultural droughts in this region. Based on revised global multi-source microwave-based SM products, the European Space Agency's Climate Change Initiative Soil Moisture (ESA CCI SM) data, the 10-day-scale soil moisture (SM) series was constructed and applied to detect droughts and analyze changes in drought characteristics, including duration, area, frequency, intensity, and severity. The results suggest that the intensity of agricultural drought in the Yunnan Province decreased, while the drought frequency increased. Drought duration increased by 20 days, collectively leading to a significant increase in drought severity in the last decade. Qujing in the east was most sensitive to agricultural drought, followed by Kunming and Chuxiong in the central area. The southwest region was prone to long drought and maintained an upward trend in terms of drought area. Regional SM with complicated temporal-spatial change patterns cannot be attributed to a single trend of "dry to dryer, wet to wetter". This study may provide insights into drought analysis in other humid regions. [ABSTRACT FROM AUTHOR]

• Revise CCI SM via a comparison with in situ observations. • Detect droughts in soil moisture by CCI SM from 1978 to 2016. • Quality control and reason analysis of long-term CCI SM. Soil moisture (SM) plays an important role in regional runoff variations, energy dynamics, and vegetation productivity. It is also widely used to detecting agricultural drought. Recently, a severe drought occurred in Yunnan Province in southwestern China, so long-term changes in surface SM were of concern. However, there were only 18 SM stations in Yunnan Province, and the longest observation was less than five years; thus, long-term changes in Climate Change Initiative (CCI) SM were investigated. CCI SM and in situ SM had similar trends of temporal variations and a systematic difference. The revised CCI SM was built by a linear regression model based on the relationship between in situ SM at each station and the corresponding grid of CCI SM. The revised CCI SM showed an abnormally low value during the severe drought in 2009, indicating that the monthly revised CCI SM could detect drought in Yunnan Province. SM drought easily occurred during the dry seasons, and the frequency of drought seems to decrease, but the severity of drought increased in the 21st century. The seasonal SM struggled to reflect drought correctly and accurately. CCI SM needs validation before use due to its variable quality. In summary, CCI SM provides a better tool than in situ SM to investigate long-term changes in SM and detect drought, and can be used for climate modeling. [ABSTRACT FROM AUTHOR]