东移西南低涡空间结构的气候学特征  

Climatic Characteristics of the Spatial Structure of the Eastward-Moving Southwest Vortex

作　　者：潘旸[1,2,3] 李建[4] 宇如聪[5] 

机构地区：[1]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029 [2]国家气象信息中心,北京100081 [3]中国科学院研究生院,北京100049 [4]中国气象科学研究院,北京100081 [5]中国气象局,北京100081

出　　处：《气候与环境研究》2011年第1期60-70,共11页Climatic and Environmental Research

基　　金：国家重点基础研究发展计划2004CB418304;国家自然科学基金40625014;40705025

摘　　要：对1991～2004年夏季(6～8月)西南四川盆地的低涡活动进行统计分类,比较分析了移出型和停滞型两类西南低涡生成初期的合成环流场,总结出影响低涡东移的三维环流结构的气候学特征:东亚中纬度地区对流层中高层的冷空气入侵造成中高层气温偏低,位势高度降低,伴随冷偏差中心南侧20°N～30°N由对流层顶至850hPa都出现偏强西风,最大的西风偏差位于长江下游地区上空200hPa。一方面,高层风速差异的纬向梯度加强了长江中游地区的高空辐散,在西南低涡东部形成有利于降水和气旋性环流发展的动力抬升机制。另一方面,对流层低层的西风偏差在青藏高原南麓至我国东部长江以南形成一条异常的水汽输送带,加强了低涡南侧的偏西风水汽输送作用,为低涡东部的降水潜热反馈作用提供了充足的水汽。西南低涡在这样有利的环流形势和水汽条件下更容易移出盆地。Based on the statistical analyses,the vortices arising in summer （JJA） from 1991 to 2004 are divided into two categories,that is,the moving and stagnant ones. Based on the comparison of composite circulation in these two kinds of vortex cases,the three-dimensional structure of the background general circulation and the influence of the moisture condition on the development and movement of the southwest vortex are studied. The results show that in the moving vortex cases,the atmosphere in the middle and upper troposphere around middle latitudes over the eastern part of the Tibetan Plateau is much colder than that in the stagnant vortex cases caused by the cold air invading. The colder air leads to the lower geopotential height,on the south side of which,the stronger westerly winds prevail from the tropopause to 850 hPa,with the maximum on 200 hPa. The great gradient of the west wind velocity difference at the upper levels enhances the divergence and upflows over the eastern part of the Sichuan Basin. And the stronger westerly winds at the lower levels result in the stronger moisture transport in the southwestern part of the Sichuan Basin. It benefits the eastward movement of the southwest vortex.

关 键 词：西南低涡 合成分析 环流背景 三维结构 水汽输送 

分 类 号：P466[天文地球—大气科学及气象学]