Spatiotemporal characteristics and onset processes of flash droughts during the growing season in Inner Mongolia, China

Flash droughts (FDs) develop quickly and can rapidly deplete soil moisture, posing significant threats to agriculture and pastoral systems. To investigate the spatiotemporal characteristics and development mechanisms of FDs in Inner Mongolia, China, and to assess the roles of key meteorological drivers in driving soil moisture variability, FD events were identified using root-zone soil moisture data during the growing seasons from 1982 to 2022. The results indicate the presence of five FD hotspot regions, located in the southern Alxa Plateau, the Hetao Plain in Bayannur, the northwestern Xilingol Plain, the western Liaohe River Plain, and the northern Da Hinggan Ling. Over 41 years, FDs occurred on average 7.44 events across the study area, with a mean duration of 9.17 pentads (1 pentad equals 5 days). The duration exhibited a significant increasing trend of 0.39 pentads/10 years. FD onsets primarily lasted for 2-3 pentads. During the FD development phase, precipitation and evapotranspiration decreased while temperature, potential evapotranspiration, incoming solar radiation, and vapor pressure deficit increased. The dominant meteorological drivers of FD development exhibited notable spatial heterogeneity across hotspot regions, and vapor pressure deficit consistently was the most influential factor. These findings improve the understanding of climate drivers at different stages of FD development and provide scientific support for early warning and prevention of droughts in Inner Mongolia.