近51年500 hPa上北极涛动的时空变化特征分析

Spatial and Temporal Variation Characteristics of Arctic Oscillation on 500 hPa in Recent Fifty-One Years

对1951-2001年北半球500 hPa高度场月、季及年平均资料分别进行EOF分析.并对EOF分析得到的第一特征向量时间系数进行功率谱分析.结果发现:北极涛动是近51年北半球500 hPa高度场异常的第一特征,方差贡献率在10%～20%之间;极区中心具有明显的偏心结构,范围冬、春季大而向高纬伸展;夏、秋季小且向极区收缩.中高纬冬季中心区范围比夏季大且系统比较集中;极地到格陵兰岛附近、西南欧洲到地中海地区、贝加尔湖到日本海以及北美洲东南部地区是500 hPa高度场上环流异常的主要发生地区;北极涛动正位相时期,冬季在20世纪90年代,春季在70年代中期以前,夏季在60,70年代,秋季在80年代中后期到90年代前期;北极涛动负位相时期,冬季在50年代,春季在70年代中期以后,夏季在50,90年代,秋季在90年代后半期.另外,只有1998年相对来说为全年各月北极涛动强年,说明1998年是近51年来气候最异常的一年.

The monthly mean normalized data of 500 hPa geopotential height field over Northern Hemisphere in 1951_2001 is used to do the EOF analysis according to the each of 12 month, respectively, and then the power density spectrum is used to study the time coefficient changes of the first eigenvector of EOF. The result show that the Arctic Oscillation is the first character of 500 hPa geopontential field circulation anomaly over Northern Hemisphere in recent fifty|one years, and the variance contribution rate is between 10% and 20%. The center at polar area has a remarkable eccentric construction. The areas of the center extend to high latitude in winter and spring, are larger and that of the center in summer and autumn are smaller to polar contracting. The central area at middle-high latitude is also larger in winter than in summer. The regions of from polar to Greenland, from Southwest Europe to Etesian, from Baikal lake to the Japanese Sea and the Southeastern of North America are the major occurring areas of 500 hPa circulation anomaly over Northern Hemisphere. For positive periods of AO, winter is in 1990′s; spring, before the middle of 1970′s; summer, in 1960′s and 1970′s; autumn, in the mid-later period of 1980′s to the early 1990′s. For negative periods of AO winter are in 1950′s; spring, after middle period of 1970′s, 1950′s and 1990′s; autumn, the later half of 1990′s. And 1998 is the most notable year of AO.