南半球环流异常与长江中下游夏季旱涝的关系

Atmospheric circulation anomalies in the Southern Hemisphere and summer rainfall over Yangtze River Valley

本文对长江中下游夏季旱涝年前期(34、、5月的季节平均)和同期(6、7、8月的季节平均)的南半球环流作对比分析,探讨南半球环流异常与长江中下游夏季旱涝的关系.结果表明前期和同期南半球环流均有显著差异,春季南极涛动对长江中下游旱涝的影响较夏季显著,南半球副热带高压在春、夏两季中有很好季节持续性.因此,春季南半球环流异常可以作为长江中下游夏季旱涝主要短期气候预测因子.南、北半球中高纬环流相互作用是长江中下游夏季降水的一个重要因素,其可能的联系机制是从南半球高纬到北半球东亚沿岸经向分布的正压遥相关.研究中还发现在长江中下游的涝年,整个对流层中南半球春、夏两季有持续增温,这说明了南北半球的温度梯度减弱也是东亚夏季风减弱的原因之一.

The relationship between the Southern Hemisphere （SH） atmospheric circulation anomalies and the summer rainfall over the Yangtze River Valley is analyzed. The results show that Antarctic Oscillation （AAO） in spring （MAM） is much remarkable than that in summer. The Subtropical High in SH has good seasonal persistence from spring to summer. Therefore, the spring SH circulation anomaly is one of important short-term climate predictors for summer rainfall over the Yangtze River Valley. The interaction of circulation at high latitudes between the Southern and Northern Hemispheres impacts the summer rainfall over the Yangtze River Valley. One possible physical mechanism for it is barotropical wave train distributed from high latitude in the SH to coasts of East Asia. Another reason is that the inter-hemispheric temperature gradient decreases due to the SH temperature increase in the whole troposphere from spring to summer, consequently causing the weaker summer Asian monsoon and more summer rainfall over the Yangtze River Valley.