Drought monitoring in Yunnan province based on CHIRPS and SPEI datasets

Yunnan Province, located at the margin of the East Asian monsoon zone, has experienced frequent drought events in recent years due to the combined influences of climate change and complex topography. These droughts exhibit pronounced spatial heterogeneity and temporal variability. To accurately identify regional drought evolution and enhance disaster response capacity, it is essential to conduct quantitative drought monitoring using high-resolution spatiotemporal datasets. This study utilizes CHIRPS satellite-based precipitation data from 2000 to 2022 and the Standardized Precipitation Evapotranspiration Index (SPEI). The Theil-Sen median trend estimator and Mann-Kendall test are employed to systematically analyze precipitation trends, drought frequency, duration, and spatial distribution patterns at the prefectural level across Yunnan Province. A threshold of SPEI ≤ -1.5 is used to define drought events. Results show that the southeastern, central, and northwestern regions of Yunnan have experienced high drought frequency over the past 23 years, with a clear intensifying trend. The cumulative number of drought events in some areas exceeded 15, with the southeastern region suffering the longest drought in 2020, lasting up to 8 months and reaching a minimum SPEI of -1.8. A significant positive correlation is found between precipitation decline and increased drought frequency, with Kunming, Yuxi, and Honghe identified as particularly vulnerable regions. This study reveals the spatiotemporal patterns and regional disparities in drought evolution in Yunnan, providing essential data support and theoretical foundation for the development of localized drought emergency response plans at the prefectural level. The findings have strong practical significance for disaster risk reduction and climate adaptation in monsoon-fringe regions.