北极涡年代际变化及其与我国春季降水的关系

基于NCEP/NCAR的500hPa再分析高度场资料计算出多年北半球及各分区的极涡面积和强度,利用线性倾向估计、小波分析及二项式滑动平均分析极涡及我国春季降水的年代际变化特征,并采用奇异值分解讨论同期及前期极涡对我国春季降水的影响。各季节极涡面积及强度均存在显著的年代际变化,在20世纪70年代中期之前有上升趋势,而后出现下降的趋势;但极涡面积总体上有显著的线性变小趋势。在60年代中前期极涡位置偏向亚欧大陆,在90年代中后期极涡位置有偏向太平洋和大西洋一带趋势。我国160站平均春季降水量经历较明显的3次上升过程和4次下降过程;华南、西南地区春季降水趋势与长江流域、黄河流域呈现两种相反的分布型;在20世纪60年代中前期、90年代初及末期,长江流域、黄河流域春季降水量偏多,而在80年代末期、90年代中期及本世纪初,华南、西南地区出现偏多。在春季,若II区(150°E～120°W)极涡面积异常大,I区(60～150°E)、III区(120～30°W)极涡强度异常弱,长江、黄河之间中游地区的降水出现负距平,广东、福建沿海降水出现正距平。前期冬季极涡比夏、秋季极涡对我国春季降水的影响更明显,特别是前冬北美区、大西洋欧洲区极涡面积的影响。

The Interdecadal Variation of North Polar Vortex and Its Relationships with Spring Precipitation in China

The area size and intensity of 500 hPa north polar vortex and four quadrants are estimated based upon 54-year NCEP/NCAR reanalysis monthly mean geopotential height data.By means of linear trend estimate,Morlet wavelet analysis and binomial coefficient smooth,the interdecadal variation characteristics of north polar vortex and spring precipitation in China are studied.The results show that:1)Seasonal average area and intensity of polar vortex exists obvious inter-decadal variation.Before the middle age of the 1970s,area size of north polar vortex trended to rise,and after that,it trended to minish,but during the size had a linear decline trend as a whole.The center of polar vortex mainly displaced towards Asia-Europe during the early and middle age of the 1960s,while trended to the Pacific and the Atlantic after the middle age of the 1990s.2)Spring average precipitation of the 160 station in China obviously increased thrice and decreased four times.The trend of spring precipitation in South and Southwest China is opposite to the Yangtze River and Yellow River valleys.During the early and middle age of the 1960s and in early and late period of the 1990s,the precipitation was more in the Yangtze River and Yellow River valleys,but during telophase of the 1980s,middle age of the 1990s and the beginning of the 21st century,the precipitation is more in South and Southwest China.3)If the area of polar vortex in quadrant II is bigger than normal,and intensity of polar vortex in quadrant I and III is weaker in spring,the precipitation is below the normal in the middle drainage area of between the Yangtze River and the Yellow River,and it exceeds the normal in the seaside area of Guangdong and Fujian.Polar vortex in winter influences more obviously next spring precipitation than the vortex of in summer and autumn,especially for polar vortex in North America and the Atlantic-Europe sections.