The connection of the Arctic Oscillation (AO) with the frequency of temperature extremes over East Asia during boreal winter has been documented by many studies. This study describes an asymmetry in the relationship between the January AO and the simultaneous cold extremes in Northeast China (NEC), and further reveals a breakdown of this relationship. It is demonstrated that the frequency of January cold extremes in NEC shows significant (insignificant) negative correlation with the simultaneous negative (positive) phase of the AO. One possible explanation for such an asymmetry is that the Arctic center of negative AO extends more southwards to Siberia compared with that of positive AO, conducive to a closer connection with the frequency of an extreme Siberian high. As a result, the frequency of January cold extremes in NEC shows a more significant relationship with the negative AO. The other related explanation is that, concurrent with the negative phase of the AO, there is an evident meridional stationary planetary wave in the upper troposphere around (30°N, 100–300 hPa), which disappears in the positive AO. Therefore, the negative AO could better reflect the fluctuation of the subtropical westerly wind and the synoptic-scale transient wave activity, which is closely related to the frequency of cold extremes in NEC. Along with a positive polarity of the AO trend since the mid-1980s, the connection between the cold extremes over NEC and the AO during January has been weakened.
大量研究表明，北极涛动与东亚冬季极端气温事件的频次存在显著的联系。本研究针对北极涛动正、负位相期间极端气温事件的发生频次，利用线性相关、合成分析等方法，发现了我国东北1月极端气温事件的频次与负（正）位相北极涛动呈显著（不显著）统计相关关系。机理分析表明，该不对称性与正、负位相北极涛动之间的空间结构差异、准定常行星波的传播差异有关