热带大气季内振荡对中国冬季持续低温事件的影响

利用1959—2011年中国522个站点冬季日平均温度资料,选出期间中国发生的持续低温事件,统计了MJO位于各位相时中国各区域发生持续低温事件的概率,并试图从垂直速度以及经向环流异常入手,研究MJO影响中国冬季持续低温事件的机制。统计研究表明,MJO位于2、3位相时,中国大部分地区发生持续低温事件的概率相对更高。中国北方部分地区在MJO位于5、6位相时,也有相对较高的概率触发持续低温事件。而MJO位于7位相时中国南方地区发生持续低温事件的概率较高。从影响机制看,MJO能够激发出西北向传播的Rossby波,引起局地Hadley环流异常,在副热带亚洲地区激发出大气异常显著的垂直运动,影响东亚地区大气环流形势,进而改变冷空气活动的路径或区域,导致中国冬季的持续低温事件发生概率的变化。

Influence of Madden-Julian Oscillation on winter persistent cold events in China

Persistent cold events (PCEs) are picked out from winter daily mean temperature datasets of 522 stations in China from 1959-2011. The frequency of PCEs occurrence was calculated when MJO was in different phases and the influence of MJO on winter PCEs in China was investigated from viewpoints of vertical motion and meridional circulation anomaly. Statistical result shows that PCEs occur more frequently in most regions of China when MJO is in phase 2 and 3. When MJO moves to phase 5 and 6, PCEs occurrence regions are confined to northern China and when MJO is in phase 7, southern China has a higher probability of PCEs occurrence. Furthermore, the possible mechanisms was investigated and indicated that MJO can lead to the local Hadley cell anomaly through exciting Rossby wave, then it is possible to affect the significant vertical motion anomalies in east Asia, finally MIO can change the paths or regions of cold air movement because of evolution of atmospheric circulation there.