登陆热带气旋引发云南强降水的环境场特征  

Ambient Field Characteristics of Westbound Landing Tropical Cyclones Impacting Rainfall Process of Yunnan

作　　者：郭荣芬 肖子牛[2] 鲁亚斌[3] 

机构地区：[1]云南省气象服务中心,昆明650034 [2]中国气象局气象干部培训学院,北京100081 [3]云南省气象台,昆明650034

出　　处：《气象》2013年第4期418-426,共9页Meteorological Monthly

基　　金：国家重点基础研究发展规划项目(2009CB421504);国家自然科学基金(40975032);云南省气象局预报员专项(YB200901)共同资助

摘　　要：应用《西北太平洋热带气旋年鉴检索系统》资料、NCEP/NCAR再分析资料及云南降水资料,对1959—2007年热带气旋(以下简称TC)西行登陆引发的云南强降水过程进行了分类统计,得到4类TC强降水环流模型,分别是TC低压环流型、TC低压外围或倒槽型、TC低压与低槽冷空气相互作用型和TC与两高辐合相互作用型。环境场特征显示,100 hPa南亚高压中心位置在90°E以西,高空东风急流提供了强大的辐散场,低空西南季风气流与TC环流相连接,高低层涡度差呈负值区分布,使TC低压环流在陆上维持或强度减弱缓慢;西南季风气流中的低空急流、副热带高压外围及TC低压东部的偏南急流共同作用,向云南输送充沛的水汽和能量,是登陆TC强降水产生的重要天气系统配置形势;强降水分布在低空急流左侧,TC低压或倒槽西北侧的正涡度中心附近;冷空气南下进入云南,增加了大气斜压不稳定,使TC外围降水增强。Using ＂the Northwest Pacific Tropical Cyclone Retrieval Yearbook System＂ data, NCEP/NCAR reanalysis data and Yunnan precipitation data, westbound landing tropical cyclones （TC） impacting the rainfall process of Yunnan during 1959--2007 are classified and analyzed in this paper. The results show that there are four types of circulation pattern including TC low circulation pattern, TC low outer circula- tion or inverted trough pattern, TC interacting with the two high-convergence pattern, and TC low pres- sure interacting with trough cold air pattern. The ambient field characteristics show that when 100 hPa high pressure in South Asia is positioned to the west of 90°E, the strong divergence zone offered by the up- per level easterly jet enhances the joining of the low level southwest monsoon flow with the TC circulation, and the difference of high- and low-level vorticities distributes negatively, making the TC low circulation maintained on land or slowing down the weakening. Abundant energy and moisture are provided for the rainstorms in Yunnan by the low-level jet of southwest monsoon, subtropical high as well as the south low level jet accompanying TC. Severe precipitation often occurs on the left side of low-level jet, near positive vorticity center of TC low or inverted trough. The atmospheric baroclinic instability increases with the advection of cold airs entering Yunnan, causing the enhancement of precipitation in the outer part of tropical cyclones.

关 键 词：西行热带气旋 强降水 分类统计 诊断分析 

分 类 号：P468[天文地球—大气科学及气象学]