Spatial and temporal patterns for the tendency of geopotential height variation over the Qinghai-Tibet Plateau during 1979~2005
1979~2005年青藏高原位势高度场变化趋势的时空特征

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 mechanism and influence of the spatial and temporal tendency of geopotential height variation over the Plateau and its regional response to global warming.