根据1966-2004年青藏高原中东部17个站点的降水、气温、地温资料,利用EOF分析以及相关分析方法研究了青藏高原中部地气温差对西藏中东部降水的影响.结果表明:西藏中东部6-9月降水EOF分析第一特征向量场的时间系数与安多的地气温差的相关系数可以达到0.7以上,而与高原中部地气温差的平均值的相关系数达到了0.8,推论青藏高原中部春末夏初的感热与西藏中东部的6-9月降水有较好的关系.其机理主要体现在两个方面:一是较强的高原中部感热可以增加空气在边界层的对流以及南北空气在高原中部的辐合;二是较强的感热可以促使高原低涡的形成,这一天气系统对青藏高原中东部的降水具有相当大的贡献,在1979年其贡献率达到50%以上.
Based on the data of daily precipitation,air temperature,ground temperature from 17 regular weather stations in the middle and east of Tibet Plateau,and by EOF analysis,the relationships between the difference of air and ground and the precipitation during June to September in middle and east Tibet were analyzed.The results show that the difference between the air and ground during May of over the central Qinghai-Xizang Plateau relates closely to the first eigenvector weight time series(EOF1) of the monsoon precipitation for the eastern part of the Plateau from June to September.At the Amdo site,the correlation coefficient exceeds 0.7,and the correlation between the EOF1 and the average of the difference at five sites(Amdo,Bange,Wudaoliang,Tuotuohe and Gaize) over the central Qinghai-Xizang Plateau can exceed 0.80.Due to sensible heat is closely related to the the difference between air and ground,this relationship suggests a mechanism of more the sensible heat flux in central Qinghai-Xizang Plateau during May causing stronger cyclonic flow and low vortices in this area,resulting in more precipitation during the monsoon season on the eastern Plateau.From May to August,1979,for example,this sensible heat effect can account for more than half of the precipitation.