江苏夏季旱涝环流演变特征分析

Analysis of circulation patterns of Jiangsu province in summer drought/flood period

利用NCEP/NCAROLR月资料和北半球500hPa逐月高度场距平格点资料,讨论江苏夏季旱涝天气气候的环流特征。研究表明:菲律宾以西太平洋暖池区OLR低值区值强弱直接影响江苏夏季降水,OLR值越低,该区辐合越强,则其北部副热带高压偏强,有利于副高的北抬和西伸,使副高北侧的雨带偏东偏北,江苏易偏旱;反之江苏易偏涝。500hPa在东亚地区南北呈"+、-、+"的纬向分布,中高纬度乌拉尔山和鄂霍茨克海地区夏季500hPa高度距平场为明显的正距平区,在该地区形成双阻或单阻有利于形势的稳定,使降水持续,江苏夏季降水偏多。

This paper uses the monthly data of NCEP/NCAR OLR and the monthly data of the composite height anomaly fields at 500 hPa in summer to discuss the circulation pattern of Jiangsu province in drought/flood period. The study shows that intension of the low OLR region in warm area of Pacific Ocean to the west of Philippines directly affects the precipitation of Jiangsu in summer. The lower OLR is, the stronger the horizontal convergence will be, at the same time, the stronger the northern subtropical high becomes, which helps extend subtropical high to north and east and move the rain belt in the north of the subtropical high to west or north. Under this condition Jiangsu is easy to be drought, and on the contrary Jiangsu is easy to be flood. The distribution of 500 hPa in north and south part of Southeast Asia is ＂ ＋, -, ＋ ＂ The summer circulation in mid-high latitude Ural Mountains and Okhotsk Sea is the high center, and the patterns of blocking high help stabilize the situation and lead to a steady precipitation. As a result it rains lot in summer.