摘要
利用青藏高原中东部地区1961～1990年2000m以上的66个台站夏季（6～8月）降水资料分析了其时空变化特征，发现高原南北降水具有反向变化的特点；结合500hPa高度场及风场资料，讨论了造成高原中东部降水异常的环流特征，指出北大西洋涛动变化可能是影响高原中东部降水的重要原因之一。与北大西洋涛动相联系的中纬度西风异常，通过对高原的西风环流的动力作用的改变，进而引起高原南北槽脊系统的同时加强或减弱，最终造成高原南北部降水的相反变化。
By using 1961 - 1990 summer (June-July-August) rainfall data from 66 stations located at more than 2000m above sea level on the central and eastern Qinghai-Xizang Plateau,the temporal evolutions and spatial structures of the summer rainfall are revealed through theempirical orthogonal function (EOF) analysis. It is found that the dominant spatial patternof the summer rainfall variation over the Plateau is a seesaw between the southern andnorthern parts and the temporal variation of the dominant pattern is closely correlated withthe North Atlantic Oscillation (NAO). A possible mechanism of the correlation is proposedon basis of statistical analyses with the geo-potential height and wind field data over theNorthern Hemisphere. In a summer when the NAO index is low, the westerlies in mid-latitudes from eastern Atlantic to western Europe increases- Enhanced westerlies will bringabout a strong flow around the Plateau when passing the Plateau and so the ridge or anticyclonic vorticity in the northern part and the trough or cyclonic vorticity are strengthened si-multaneously- In this case, the summer rainfall is usually above the normal in the southernPlateau but below the normal in the northern Plateau- In a summer with a high NAO index, the above processes are opposite.
出处
《气象学报》
CSCD
北大核心
1999年第5期561-570,共10页
Acta Meteorologica Sinica
基金
国家与中科院青藏研究项目!KZ951-A1-402
中科院"九五"重大项目!919980408
关键词
青藏高原
夏季
降水
经验正交函数
北大西洋涛动
Qinghai-Xizang Plateau, Summer rainfall, EOF, North Atlantic Oscillation, Westerly circulation
