Analyses on Changes of Surface Temperature over Qinghai-Xizang Plateau

The basic climate characteristics of winter,summer and annual mean surface temperatures were analyzed by using 86 stations over the Qinghai-Xizang Plateau(QXP) during the period from beginning to 2001, and the spatial anomaly structure and time evolution tendency have been systematically diagnosed by principal component analysis, a periodic function and a random function and power spectral analysis methods. The result shows that the surface temperature is a function of elevation above sea level and latitude. The higher the elevation above sea level and latitudes are, the lower the surface temperature is. The annual mean surface temperature is 14.9℃ inChayu of the Yaluzangbu River, and the maximum value of surface temperature in summer is 23.0℃in Germu of Chaidamu Basin. The minimum value of annual mean surface temperature in center of Plateau is -0.2, in winter, -14.2 ～-15.8℃, in summer, 9.8℃at Qingshuihe, The first loading vector of surface temperature anomaly over Plateau is with the same sign in whole Plateau. The second loading vectors have differences in the north and south. The variation of the first principal component had an obvious warming trend in the last 30 years, but the second principal components were weak cooling trend, and there are quasi-three to sixyear periodic oscillations for the interannual variation. The rates of linear temperature rising along north-and-south sections of railways are 0.42~0.58℃/10a, and the center is 0.32~0.39℃/10a.