江南春季连阴雨的频数特征及其前期环流信号

围绕发生在江南地区的春季降水,旨在分析江南春雨发生频数的主要特征及其与前期的副热带急流和温带急流的联系。结果表明,江南春雨以持续4 d及以上的连阴雨为主(简称春季连阴雨),主要发生在13—27候,分布于(22.5~30 °N,105~120 °E)的江南地区。春季连阴雨发生频数在江南地区整体呈减少趋势,年际变率全场差异不大。江南春季连阴雨的主要时空异常模态表现为全场一致变化,其时间序列以年际变率为主并呈现多时间尺度特征。从前期信号来看,第13候(即春雨发生时)的前10天至前35天内,当持续存在偏弱的温带急流和偏北的副热带急流共同配置时,有利于春雨期连阴雨事件的发生。

Frequency features of spring continuous rain over southern China and its previous circulation signals

In this paper, the frequency variation of spring persistent rain(SPR) and its relationship with previous East Asian subtropical jet and polar front jet are investigated. The results indicate that the SPR is the longer-persistent (more than 4 days) rainfall event which is identified as Spring Continuous Rain (SCR)over southern China and usually occurs in the region of 22.5 °N-30 °N,105 °E-120 °E and spans in 13^th-27^th pentads. Decreasing tendency of SCR is evident in the whole southern China and a quite consistent interannual variation covers the entire region. A homogenous pattern can be identified for the spatial-temporal variation. The principal component contains multi-time scales, and the primary one is the interannual variability. During the period of 10 d to 35 d before the 13^th pentad, when persistent weakening polar front jet and northward movement of subtropical jet simultaneously exist, it becomes prior signal of easy occurrence of SCR.