中文摘要：

利用NCEP/NCAR位势高度再分析资料分析了1979～2005年青藏高原及其邻近地区30hPa、100hPa、300hPa和500hPa位势高度场变化趋势的时空特征。研究表明：（1）1979～2005年青藏高原区域平均位势高度场在对流层中层存在上升趋势,且主要发生在冷半年;随着等压面的升高,高度场上升趋势减弱;到平流层高度场呈显著降低趋势,且主要发生在暖半年。（2）从空间上看,平流层位势高度场年平均变化整体呈显著降低趋势,大致呈纬向分布,南部降低趋势强于北部,特别是高原东南、孟加拉湾北部降低趋势最强;对流层中层位势高度场变化趋势以上升为主,高原东北部上升趋势尤其显著。（3）尽管与高原各层位势高度值本身相比,变化趋势是一个小量,但国内外不同区域及不同空间尺度的研究都发现有类似现象,故对此应给予重视。今后应进一步加强青藏高原位势高度场时空变化趋势的驱动机制、影响及其对全球变暖的区域响应研究。（4）1979年以来NCEP/NCAR位势高度再分析资料用于青藏高原及其邻近地区的气候变化研究是有效的。

英文摘要：

With the adoption of Durbin-Watson（DW） Autocorrelation Test,Ordinary Least Squares（OLS） trend analysis and other related statistical methods,the spatial and temporal patterns for the tendency of variation in 30-,100-,300-and 500-hPa geopotential heights over the Qinghai-Tibet Plateau and its margins（70°～110°E,20°～45°N） during 1979 2005 are analyzed using the 2.5°×2.5°grid geopotential height data extracted from NCEP/NCAR Reanalysis.The main results and discussions are summarized as follows. The regional mean annual geopotential height showed an increasing tendency in the mid-troposphere,which mainly occurred in the winter half-year.With the elevation of isopiestic surface,the increasing trend would be weakened.And the regional mean annual geopotential height decreased significantly in the lower stratosphere particularly in the summer half-year.As for the spatial distribution of mean annual geopotential height,the remarkable declining trend was observed to be roughly latitudinal in the lower stratosphere（30-hPa）,which was stronger over the southern than the northern Plateau with the most significant decline over the southeastern Plateau and the northern Bengal Bay.On the contrary,the mid-troposphere（500-hPa） was dominated by the increasing trend of mean annual geopotential height in particular over the northeastern Plateau. Although the variation tendency is minor compared with the geopotential height itself at any level,similar phenomena have been detected in different regions and at different spatial scales,for which much more attention should be paid.The variation of geopotential height filed is related closely not only with the change of atmospheric circulation,but also probably with global warming,the increase of equatorial sea surface temperatures,ozone concentration changes,and so on.And the variation of geopotential height field over the Plateau is correlative intimately to the regional climate change.Consequently furthermore research should be strengthened on the driving mec