青藏高原低涡活动对降水影响的统计分析

Statistical Analysis on Influence of Qinghai-Xizang Plateau Vortex Activity on Precipitation in China

利用1998—2004年逐日08:00(北京时,下同)和20:00 500hPa高空图、日雨量和青藏高原低涡(下称高原低涡)切变线年鉴资料,统计分析了冬、夏半年不同生命史的高原低涡对我国和四川盆地东、西部降水的影响。结果表明,冬、夏半年高原低涡以东部涡占多数,6-10月有三分之一的东部涡能移出高原。冬半年高原低涡出现次数少,约占全年的五分之一,但也可造成高原及其周边地区的雨雪天气,特别是生命史超过36h以上的高原低涡有近半数可移出高原,造成高原区域暴雨雪,四川盆地中雨,半数可造成云南大雨雪或暴雨雪。夏半年,随着低涡生命史的增长,高原低涡影响高原及其周边地区和我国其他地区的降水范围和强度在增大,生命史超过60h以上的高原低涡可造成高原暴雨、甘肃中雨以上、四川盆地暴雨或大暴雨及云南大部分地区大雨以上的降水,每年都有1～5次可影响到华中、华东地区产生大雨以上的降水。100°E以东的高原低涡,不论是否移出,均可造成四川盆地中雨以上的降水。影响四川盆地降水的高原低涡以偏东路径为主,但东南路径影响更强。

Based on the daily synoptic maps at 08：00 and 20：00 on 500 hPa from 1998 to 2004, the yearbook Qinghai-Xizang Plateau vortex, the activities of the plateau vortex in the winter half-year and the summer half-year, and the different life time of the plateau vortex influences on the rainfall in China and Sichuan basin are analyzed with the statistical-synoptic method. The results show that the eastern vortices appear in the most time during the summer half-year and the winter half-year. From June to October, one third of the vortices can move out of the plateau. The number of the plateau vortiex reduces in the winter half-year （about 1/5 of the whole year vertices）. However, those vortices in the winter half-year can cause the rain and snow weathers in Qinghai-Xizang Plateau and its neighboring regions. Especially, about half of the plateau vortices, which last for more than 36 h, move out of the Plateau and cause the snowstorm in the Qinghai-Xizang Plateau, the moderate rainfall in Sichuan Basin and snowstorm or heavy rain in Yunnan Province at the same time. Longer life time the Plateau vortices have in summer half-year, larger scope and intensity of precipitation in the Plateau and neighboring regions happen. The plateau vortices, which last for more than 60 h, can cause the heavy rain in the Qinghai-Xizang Plateau, the moderate rainfall in Gansu Province, the heavy rain or rain storm in Sichuan Province, and the half of heavy rainfall in Yunnan Prov- ince. Such vortices can even cause from moderate to heavy rain in the central and eastern China, one to five times per year. The plateau vortices, which move to the east of 100°E, can cause the moderate rain in Si- chuan Basin. These vortices moving tracks influence to the rainfalls in Sichuan Basin are mostly the eastern direction. However, those in the southeast direction normally have much influence on the rainfall in Si- chuan Basin.