盐城地区秋季连阴雨天气的环流特征及其成因分析

Analysis on Circulation Characteristic and Cause of Continuous Autumn Rain in Yancheng Area

摘要: 本文利用1953~2016年盐城地区逐日降水和日照资料，给出了盐城地区秋季连阴雨的定义，统计了盐城秋季连阴雨和不同级别(7~9 d、10~12 d和13 d及以上)秋季连阴雨的所有过程，并分析盐城地区秋季连阴雨期间和不同级别秋季连阴雨期间的大气环流特征。结果表明：在500 hPa，副热带高压位置是偏北的，中高纬的东亚大槽和乌拉尔山长波脊是加深的，有利于引导副高西北侧的偏南风与东亚大槽后的偏北气流在盐城地区交汇；850 hPa上来自北方的冷空气与南方的暖湿气流在此辐合，并受到异常低压切变控制，偏南气流异常强盛，有利于水汽的输送；贝加尔湖与巴尔喀什湖之间的阻塞高压是增强的，有利于北方冷空气持续南下；沿120˚E的经向垂直环流发现，盐城地区处在上升气流控制，低层上升运动明显。总之，这样的配置有利于盐城地区产生连阴雨天气。另外不同级别连阴雨期间也存在差异，主要表现在500 hPa上副热带高压越偏北，两大湖之间的阻塞高压偏弱，盐城地区垂直运动越旺盛，越有利于形成严重的连阴雨天气。

Abstract: Based on the daily precipitation and sunshine data of Yancheng area during 1953 and 2016, we formulate definition of continuous autumn rain in Yancheng area. Then we count all the processes of continuous autumn rain and continuous autumn rain of different levels (7 - 9 d, 10 - 12 d, and 13 d and above). The circulation characteristics of continuous autumn rain and continuous autumn rain of different levels are analyzed. The results show that: 1) During the continuous autumn rain in Yancheng area, in the 500 hPa geopotential height field, the position of the subtropical high is north and the East Asian trough and the long wave ridges in the Ural Mountains in the mid-high latitudes are deepened. They are all conducive to guiding the southerly winds on the northwest side of the subtropical high and the northerly airflow behind the East Asian trough to meet in the Yancheng area. On 850 hPa, the cold air from the north converges with the warm and humid air from the south, and this area is controlled by abnormal low-pressure shear. The southerly airflow is extremely strong, which is conducive to the transport of water vapor. The blocking high pressure between Lake Balkhash and Lake Baikal is enhanced, which is conducive to the continuous cold air in the north. Along the 120˚E meridional vertical circulation, it is found that the upper part of the Yancheng area is controlled by updraft, and its ascending motion is obvious. In short, such a configuration is conducive to the continuous rainy weather in Yancheng area. In addition, there are also differences in circulation between continuous autumn rain of different levels. Mainly, when the subtropical high is more northerly, the blocking pressure between the two great lakes is weaker, and the vertical motion above the Yancheng area is more vigorous, which are more conducive to the formation of severe continuous autumn rain in Yancheng area.