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

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 Province.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 Sichuan 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 Sichuan Basin.