Spatiotemporal characteristics and climatic drivers of flash drought events in the Weihe River Basin*

To clarify the evolution and climatic drivers of flash drought events in the Weihe River Basin, flash droughts were identified using a three-dimensional clustering method based on ERA5-Land soil moisture and meteorological data. Spatiotemporal characteristics were systematically analyzed, and the dominant climatic drivers were examined using principal component analysis. Results showed the following: ① From 2000 to 2024, 68 flash drought events were identified, with an average frequency of approximately 2.72 events per year and an average duration of 36.5 d per event. Events in the southern Jinghe River Basin lasted longer （50—90 d） and were more likely to develop into large-scale, high-intensity events. ② Flash droughts mainly migrated toward the west-northwest, east-southeast, and east-northeast （12, 10, and 9 events, respectively）. Their migration distance, affected area, and severity were greatest toward the south-southwest. ③ The thermal–atmospheric evaporative demand factor and water supply factor were the first and second principal components, PC1 and PC2, influencing flash droughts, explaining 63.2% and 16.4% of the total variance, respectively. During flash drought periods, PC1 scores increased significantly （+6.95）, whereas PC2 scores decreased markedly （−1.52）. These findings indicate that flash drought events in the Weihe River Basin develop primarily under enhanced thermal–atmospheric evaporative demand, compounded by water supply deficits. Overall, the results provide a scientific basis for flash drought monitoring, early warning, and risk management in the Weihe River Basin.