2012年1月浙江低温连阴雨的背景场与成因分析

Analysis on the Background and the Cause of the Cold and Rainy Weather in Zhejiang in January 2012

利用NCEP/NCAR再分析资料与NOAA资料,分析了2012年1月浙江低温连阴雨雪天气的背景场与相关成因。结果表明:大尺度环流异常是本次低温连阴雨天气的主要背景场:北极涛动较弱且在1月中下旬出现转折;乌拉尔山高压脊偏强并向极地伸展;西太平洋副热带高压较常年偏西偏强,保证冷暖空气在浙江上空交汇从而导致低温连阴雨的发生;中低层水汽通量场对连阴雨有较好的指示作用;低空能量锋区的变化与连阴雨过程也是基本同步的。拉尼娜事件的发展对我国冬季低温有显著的前期效应;北太平洋海温持续偏高有利于东亚冬季风偏强。

Based on the NCEP/NCAR reanalysis data and NOAA data, the background and the reason of the cold and rainy weather in January 2012 in Zhe jiang is analyzed, and the results show that the large scale abnormal circulation is the main background field： AO is weak and turned in late January; while Ural ridge is strong and stretches to the polar, and the western Pacific Subtropical high strengthens and shifts westward, ensure the intersection of cold and warm air over Zhejiang which leads to the cold and rainy weather; Low-rise vapor can well indict the rainy days and the low energy frontal zone changes synchronously with rainy periods. Development of La Nina has a significant effect on cold weather and the remaining high north Pacific SST is benefit for stronger east Asian winter monsoon.