ABSTRACT Under global warming, extreme precipitation events (EPEs) are becoming more frequent and drawing increasing attention. However, most research defines EPEs based on statistical thresholds (e.g., 95th percentile), which may not capture their catastrophic potential. Through analysis of four cases in China's Henan Province, including the 2021 Zhengzhou and 1975 events, this study investigates the mechanisms that transform extreme precipitation into catastrophic events. Using Lagrangian moisture tracking and watershed segmentation algorithms, we found that all EPEs in Henan share a dominant southeastern moisture transport pathway from the Western Pacific Ocean, differing from the climatological southwestern monsoon pattern. Their circulation is characterised by an anomalously northward‐shifted Western Pacific subtropical high and concurrent tropical cyclone activities. What distinguishes catastrophic precipitation events (CPEs) is their ‘moisture transport structure stability’—characterised by synchronised interaction between tropical cyclones and the subtropical high, creating atmospheric blocking patterns and stable moisture channels. Three precursor signals for CPEs were identified: large‐scale circulation patterns featuring synchronised tropical cyclone‐subtropical high interactions, sustained low‐level jets concentrating moisture transport below 900 hPa, and persistent atmospheric circulation maintaining organised moisture channels. These findings reveal key mechanisms transforming extreme precipitation into catastrophic events and provide insights for improving extreme weather forecasting in monsoon regions.
Zhao et al. (Sun,) studied this question.
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