This study identified three distinct circulation patterns that induce enhanced intraseasonal precipitation events (IPEs) over South China (SC) in boreal winter based on observational data of 1979–2016. The three categories account for 45%, 33% and 14% of total IPEs, respectively. In Category I, a cyclonic anomaly with quasi-barotropic vertical structure propagates southward from the northern Asia while no signal of the Madden–Julian Oscillation (MJO) is observed. Category II (III) is featured by a fast (slow)-propagating MJO that shows suppressed (enhanced) convection over the equatorial western Pacific (Maritime Continent) during the peak-wet phase of SC. The common process responsible for the onset of IPEs is boundary-layer moistening dominated by mean moisture advection due to intraseasonal southerly wind. For Category I, the anomalous southerly arises from the southwesterly to the southeast of the mid-latitude cyclone. For Category II, it is attributed to the southwesterly to the west of the anticyclone over the northwestern Pacific, as a response to the suppressed MJO convection over the western Pacific. For Category III, it is due to the southwesterly to the east of the cyclone over India in response to the enhanced MJO convection over the eastern Indian Ocean. The moisture origins for the three categories are also distinguishable.

本研究根据 1979 年至 2016 年的观测数据确定了三种不同的环流模式，这些环流模式会导致北方冬季华南 (SC) 季内降水事件 (IPE) 增强。这三个类别分别占 IPE 总数的 45%、33% 和 14%。在Ⅰ类中，具有准正压垂直结构的气旋异常从亚洲北部向南传播，而没有观察到马登-朱利安振荡（MJO）的信号。II (III) 类以快速（慢速）传播的 MJO 为特征，在 SC 的湿峰期显示赤道西太平洋（海洋大陆）上空的对流受到抑制（增强）。引起IPEs的共同过程是边界层湿润，主要是由于季节内南风引起的平均水分平流。对于第一类，异常南风起自中纬度气旋的西南向东南。对于 II 类，它归因于西北太平洋上空反气旋以西的西南方向，作为对西太平洋上空 MJO 对流抑制的响应。对于 III 类，这是由于印度洋东部的 MJO 对流增强，气旋在印度以东的西南方向。这三个类别的水分来源也是可以区分的。这是由于印度洋东部的 MJO 对流增强，印度洋上空向西南偏东。这三个类别的水分来源也是可以区分的。这是由于印度洋东部的 MJO 对流增强，印度洋上空向西南偏东。这三个类别的水分来源也是可以区分的。