Changes of the Differences between Ground and Air Temperature over the Qinghai-Xizang Plateau
青藏高原地气温差变化分析

The difference between ground soil and air temperature(Ts-Ta) was analyzed and studied by using the data of ground and air temperature of 99 stations over the Qinghai-Xizang(Tibet) Plateau from 1960 to 2000,and its spatial distribution and time changing tendency have been diagnosed by principal component analysis and power spectral analysis methods.The results show that the values of(Ts-Ta) are the biggest in June and the smallest in December.The first three loading eigenvectors reflecting the main spatially anomalous structure of(Ts-Ta) over the Qinghai-Xizang Plateau contains the contrary changing pattern between the northwestern and the southeastern regions,the pattern response of the sea level elevation and the geography,and the pattern response of the distribution of the permafrost.There are four patterns of time evolution including the patterns of monotonous increasing or decreasing trends,the basic stability pattern and the parabola pattern with the minimum value.(Ts-Ta) has a periodic variation of about 2 years.According to the spatial distribution of the third loading eigenvector of(Ts-Ta) over the Qinghai-Xizang Plateau in cool season,the permafrost response region and the seasonal frozen ground response region are identified.