Hydroclimatic Controls on Flash Drought Development in Northeast Asia: Roles of Atmospheric Demand and Water Availability

ABSTRACT As climate change accelerates the hydrological cycle, flash droughts (FDs) have emerged as a critical challenge for water, agriculture, and ecosystem management. This study analyzes FD events across Northeast Asia (NEA) from 2000 to 2024 using the Standardized Evaporative Stress Ratio (SESR)‐based approach, focusing on spatial distribution, temporal evolution, and underlying mechanisms. Over 50% of FD events occurred in northeastern cold climate zones dominated by forests and croplands, and arid, barren western regions. Northeastern regions experienced shorter drought durations due to larger water holding capacity and wetter climates, while arid zones exhibited prolonged events, often exceeding 45 days. Spring FDs peaked in northeastern NEA, while summer FDs dominated western zones during August and September. Using a novel classification framework, we categorized FD events into three cases based on variations in actual evapotranspiration (AET) and potential evapotranspiration (PET): the Both‐driven (Case 1), AET‐driven (Case 2), and PET‐driven (Case 3) cases. Case 1, the most common type, accounted for 67.4% of total events and reflected balanced declines in AET and increases in PET across all regions. Case 2 (16.9%), driven by reductions in water availability, was concentrated in arid, barren regions during late summer to autumn, where soil moisture (SM) deficits restricted AET. Case 3 (15.7%) occurred in humid, energy‐limited forests and croplands in spring, triggered by elevated atmospheric demand despite SM availability. By introducing a novel classification framework, this study highlights how interactions between atmospheric demand and water availability drive FD development across diverse hydroclimatic and seasonal conditions.