Two Distinct Types of 10-30-day Persistent Heavy Rainfall Events over the Yangtze River Valley
Two Distinct Types of 10-30-day Persistent Heavy Rainfall Events over the Yangtze River Valley
复制标题
长江流域两类不同类型的10~30天持续性强降雨过程
DOI：
10.1175/jcli-d-20-0741.1
复制
发表时间：
2021-09
影响因子：
4.9
通讯作者：
Tim Li
中科院分区：
文献类型：
--
作者：
Yifeng Cheng;Lu Wang;Tim Li
摘要分析了1961-2017年长江中下游地区夏季10-30天过滤持续性强降水事件的大尺度环流异常。根据西太平洋副热带高压和南亚高压的异常配置，在丰水期将太平洋副高异常分为两类。一种是以南亚高压向东延伸为特征的PSAH型，另一种是以南亚高压向西退缩为特征的NSAH型，它们都表现为西太平洋高压向西延伸。这两种类型的PHRE都是由梅雨锋系统控制的。低层环流异常对暴雨的发生起着重要作用，但作用途径不同。在暴雨发生前，PSAH事件在西北太平洋（WNP）上空形成一个强的反气旋环流异常，与之相关的西南风异常在中国东南部盛行，它将水汽平流输送到MLYV，使边界层增湿，诱发大气对流不稳定。对于NSAH事件，WNP反气旋环流很弱，而在MLYV以北观察到强烈的偏北风。它带来的冷空气团南下，有利于启动锋面降水的MLYV。中高纬度异常环流的转移是造成中高纬度高层环流异常的主要原因。降水生成后，降水对低层和高层环流异常产生影响。
AbstractLarge-scale circulation anomalies associated with 10-30-day filtered persistent heavy rainfall events (PHREs) over the middle and lower reaches of the Yangtze River Valley (MLYV) in boreal summer for the period of 1961-2017 were investigated. Two distinct types of PHREs were identified based on configurations of anomalies in western Pacific subtropical high (WPSH) and South Asian High (SAH) during the peak wet phase. One type named as PSAH is characterized by eastward extension of the SAH while the other named as NSAH is featured by westward retreat of the SAH, and they both exhibit westward extension of the WPSH. Both types of PHREs are dominated by Mei-yu frontal systems. The lower-level circulation anomalies play a crucial role in initiating rainfall but through different processes. Prior to rainfall occurrence, a strong anticyclonic circulation anomaly is over the western North Pacific (WNP) for the PSAH events and the related southwesterly wind anomaly prevails over the south-eastern China, which advects moisture into the MLYV, moistens the boundary layer, and induces atmospheric convective instability. For the NSAH events, the WNP anticyclonic circulation is weak while a strong northerly wind is observed north of the MLYV. It brings cold air mass southward, favoring initiating frontal rainfall over the MLYV. The formation of upper-level circulation anomalies over the MLYV is primarily due to the shift of anomalous circulations from mid-high latitudes. After the rainfall generation, the precipitation would influence the lower- and upper-level circulation anomalies.