Revealing Circulation Patterns Responsible for Extreme Precipitation Events Over the Hai River Basin From Moisture Transport Perspective

In July 2023, an extreme precipitation event (EPE) caused severe damage and nearly 100 fatalities in the Hai River basin, North China. Using a Lagrangian approach, we investigated the moisture transport regime and identified the circulation pattern responsible for the EPE. The primary moisture sources were the northwest Pacific (24%), southeast China (21%), and the South China Sea (20%). The circulation pattern, featuring the western Pacific subtropical high to the northeast, tropical cyclone KHANUN in the northwest Pacific, and a low-pressure system southwest of the Hai River Basin, predominantly controlled the moisture transport. We discovered that an unprecedented EPE in 1963 exhibited a similar circulation pattern. By classifying historical EPEs into three categories based on seven atmospheric predictors, we identified circulation patterns associated with disaster-prone events. The most frequent category is characterized by a circulation pattern with positive geopotential height anomalies in northeast Asia and negative anomalies to the south, extending from the northwest Pacific to the Hai River Basin. This classification provides insights into the atmospheric conditions conducive to severe EPEs in the region.