北极涛动、极涡活动异常对北半球欧亚大陆冬季气温的影响

利用1951-2012年NCEP/NCAR全球月平均500 hPa高度场、气温场等再分析资料，北极涛动（AO）指数，北半球及其4个分区的极涡指数等资料，分析极涡和AO对北半球特别是欧亚大陆冬季气温异常分布的影响。北半球极涡面积指数与北半球气温相关场呈由北向南的“+、-”分布，显著正相关中心位于极区，显著负相关中心位于欧亚大陆中高纬度地区；AO指数与气温的相关场分布与此反位相。极涡各分区面积指数体现与各大洲气温显著相关的地域特征，尤其是亚洲极涡面积指数比AO的相关区域更偏向亚洲和中国东部及沿海地区，能表征亚洲大陆冬季风向中低纬度爆发的某些特征。2006年以来AO指数呈较明显的下降趋势，北半球、亚洲区极涡面积指数呈显著的上升趋势，这是有利于欧亚大陆近几年连续冬季气温异常偏低的年代际背景；2009-2011年北半球欧亚大陆冬季大范围低温事件，不仅与冬季AO负位相明显变强有关（2011年除外），与北半球以及亚洲区极涡面积指数偏大联系更为密切，亦表明该区域冬季变冷的自然变率明显增强。

Impacts of Arctic Oscillation and Polar Vortex Anomalies on Winter Temperature over Eurasian Continent

By using NCEP/NCAR monthly reanalysis dataset, Arctic Oscillation (AO) indices, the Northern Hemispheric (NH) and its four sectorial polar vortex (PV) area and intensity indices for the period 1951-2012, the relationships between PV, AO and the winter air temperature anomalies over NH continents, especially over Eurasian Continent were investigated. Results indicate that the correlation coefficients between AO index and the winter air temperature over NH showed a “-, +” pattern from the polar region to Eurasian Continent with the most significantly negative correlation center in the polar region and the significantly positive center in the Eurasian mid-high latitudes, but the correlation coefficients between NH’s polar vortex area indices and winter temperatures over NH exhibited a “+, -” pattern. In contrast to the AO index, the significant correlation area between Asian sector polar vortex area indices and winter temperatures expanded southeastward to eastern China, thus revealing some characteristics about the outbreak of the Asian winter monsoon from East Asian mid-high latitudes to the mid-low latitudes. The AO index has shown a decadal decreasing trend whereas both the NH’s and Asian sector polar vortex area indices have exhibited a decadal increasing trend since 2006, this decadal background provided the favorable conditions for the continuous anomalous low winter air temperature over the Eurasian Continent in recent years. The wide range of anomalous low winter air temperature during 2009-2011, was related to the enhancement of the negative phase of AO (except in 2011) and more closely related to the increase of NH’s and Asian sector polar vortex areas. This also indicates that the natural variability of winter cooling was obviously enhanced in Eurasian Continent.