北半球绕极涡的变异及其与我国气候异常的关系

VARIABILITY OF THE NORTHERN CIRCUMPOLAR VORTEX AND ITS ASSOCIATION WITH CLIMATE ANOMALY IN CHINA

本文利用近50a大气再分析资料和中国站点观测资料，通过定义绕极涡的总体面积指数，分析了北半球绕极涡的变异特征及其与我国气候异常的关系，通过考虑绕极涡的局地变异和利用SVD分析方法揭示了绕极涡的局地变异与我国气候变异的关系。结果表明：北半球绕极涡的总体面积变异表现为一致性的扩张或收缩变化特征，近50a来其总体面积具有收缩的趋势，这与全球增暖尤其是极区增暖有密切关系；叠加在这种趋势之上的既有年际变化又有年代际变化，主要周期大约是3～5a和8～12a。因此，研究绕极涡与我国气候的相关时分时间尺度来考虑更合理。北半球绕极涡的总体面积变异与我国气候异常的关系主要体现在年代际时间尺度上，当北半球绕极涡总体一致性收缩时，冬季我国大部分地区的气温都会随之变高，而降水偏多；夏季东北、华北、西南和华南地区气温偏高，降水偏少，而江淮流域气温偏低，降水偏多。反之亦然。北半球绕极涡的局地变异主要体现在西风带长波振幅的变异上，而其与我国气候异常的联系主要表现在年际时间尺度上，当东亚大槽减弱时，冬季我国中、东部大部分地区气温偏高，降水偏多；夏季江淮流域和四川盆地气温偏低，其它地区气温偏高，降水变化不明显。反之亦然。

The variability of the northern circumpolar vortex and its association with the climate anomaly in China is investigated with using near 50 a NCEP/NCAR reanalysis data of atmosphere and observation data of Chinese stations, by defining a total area index of the circumpolar vortex. By analyzing the local variation of circumpolar vortex and using SVD method, the relationship between the local variation of the circumpolar vortex and the climate anomaly in China is documented. The variability in total area of the northern circumpolar vortex is characterized by consistently expanding or contracting. The linear trend over last 50 years is found to be contracting, which is closely associated with global warming, especially with polar warming. Superimposed on this trend are the interannual to interdecadal variabilities with principal periods 3-5 years and 8-12 years. So, it would be rational to investigate relationship between the circumpolar vortex and the climate in China with different time scales. It is found that such a relationship is more evident on the interdecadal time scale. When the northern circumpolar vortex consistently contracts, most of China tends to be warmer and wetter during winter, while Northeast China, North China, Southwest China and South China are warmer and drier and Changjiang-Huaihe River valley is cooler and wetter during summer; and vice versa. The local variation of the northern circumpolar vortex is mainly associated with amplitude variations of the long wave in the midlatitude westerly belt. Its association with the climate anomaly in China is mainly on the interannual time scale. When East Asian trough weakens, east and central China are warmer and wetter during winter, while Changjiang-Huaihe River valley and Si- chuan Basin are cooler and no obvious relation is found in precioitation during summer;and vice versa