Synoptic regimes contributing to summer clustered extreme precipitation events in Northeast China

Résumé fourni par la source

Recently, the frequency and intensity of clustered extreme precipitation events (CEPEs) have increased markedly worldwide, causing considerable economic losses and human fatalities. In this study, four synoptic patterns responsible for summer CEPEs over Northeast China in the period 1961–2022 were identified through spectral clustering. They were characterized by an eastward-moving low-altitude vortex (Pattern 1), southwesterlies (Pattern 2), a locally intense low-altitude vortex (Pattern 3), and northward-moving tropical cyclones (Pattern 4). Patterns 1 and 2 were primarily driven by northward extension of the western North Pacific subtropical high (WNPSH) and northeastward extension of the South Asian high (SAH) between 24 h before CEPEs and the occurrence day. Pattern 3 was primarily influenced by westward WNPSH extension and eastward SAH extension during the day preceding CEPEs. Finally, eastward WNPSH retreat and westward SAH extension promoted the occurrence of Pattern 4. The net moisture amount over Northeast China, notably via a net meridional influx, considerably increased 24 h before CEPEs under all synoptic patterns, peaking 6 h earlier under Patterns 1 and 2 and 12 h earlier under Patterns 3 and 4. This study provides a robust assessment of prerequisite conditions for the occurrence of CEPEs. 近年来, 全球区域性极端强降水事件 (CEPEs) 频发且强度加剧, 对经济和人民生活造成了巨大损失.本文利用谱聚类研究了1961−2022年中国东北CEPEs相关的四种典型环流型, 即为低涡东移型 (类型1) ,西南风增强型 (类型2) ,局地增强低涡型 (类型3) 和热带气旋北上型 (类型4) .CEPEs 发生前 24 小时至当日, 西北太平洋副热带高压 (WNPSH) 北抬与南亚高压 (SAH) 向东北延伸共同驱动了类型1和类型2事件的形成;类型3事件则受CEPEs前1日WNPSH西伸与SAH东伸的影响;WNPSH东退与SAH西退促成了类型4事件的发生.在四种环流型下, 东北区域净水汽收入 (特别是净经向水汽输入) 在CEPEs前24小时显著增加:在类型1,2 (3,4) 中, 净水汽输入在CEPEs 发生前6小时 (12小时) 达到峰值.本研究可为区域性极端强降水预测提供可靠的前兆信号.

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