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Dominant circulation patterns of warm-season heavy precipitation in North China and the extremity analysis of the rainstorm in July 2023
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DOI：10.1016/j.atmosres.2026.108947.png)
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Abstract
En 中文
Extreme precipitation (EP) events in North China (NC) have become more frequent and intense in recent decades. Yet it remains unclear which circulation configurations most facilitate EP over NC, how these patterns have evolved, and how strongly they are modulated by tropical cyclones (TCs). This study classifies daily 500 hPa geopotential height fields during the warm seasons of 1979-2023 into four objectively defined circulation types (T1-T4) using the self-organizing map (SOM) method. T3, characterized by a northwestward-extended western Pacific subtropical high (WPSH) and southerly moisture inflow ahead of a mid-latitude trough, is the pattern most conducive to EP in NC. Moreover, the frequencies of both T3 circulations and associated EP-days have increased significantly, suggesting that NC is entering a wetter climate regime with higher EP risk. Further classification of T3 at 850 hPa identifies T3-3, a north-south dipole pattern strongly influenced by TCs, producing the most intense and persistent rainfall along the Taihang-Yanshan foothills. The record-breaking July 2023 (23 & sdot;7) rainfall event occurred under this subtype. During this event, an anomalously northwestwardextending WPSH, persistent southeasterly inflow, TCs Doksuri and Khanun, and local orographic lifting jointly enhanced moisture convergence and amplified precipitation intensity. The daily regional-mean integrated moisture flux divergence (IMFD) exceeded the 85th percentile of all warm-season EP events. Despite the markedly favorable large-scale environment, ERA5 captured only 57.3% of the median observed extreme rainfall during the 23 & sdot;7 event, highlighting that the extreme intensity was also critically dependent on local orographic lifting and mesoscale convective systems.
Keywords:
Dominant circulation patterns
Warm-seasons heavy precipitation
North China
23 & sdot
7 extreme precipitation event
Extremity analysis
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