热带印度洋SST海盆模态的“充电/放电”作用--对夏季南亚高压的影响

The "charge/discharge" roles of the basin-wide mode of the Indian Ocean SST anomaly——influence on the South Asian High in summer

根据观测资料和海气耦合模式初值试验结果,通过比较分析热带太平洋SST主模态（ENSO模）和热带印度洋SST主模态（海盆模）对夏季南亚高压的影响,揭示了印度洋海盆模的“充电/放电”作用：赤道中东太平洋海温异常首先对印度洋进行“充电”,形成热带印度洋SST对太平洋EN-SO的响应模态——海盆模。该模态在ENSO发生翌年春季达到峰值位相,而且有很好的持续性,可以从春季持续到夏季,该暖（冷）模态可以引起大气的“Matsuno-Gill pattern”响应,并通过亚洲夏季平均西南季风的异常水汽输送等使得夏季南亚高压偏强（弱）,即为“放电”过程。而赤道中东太平洋海温异常对夏季南亚高压的直接影响并不显著,并指出了夏季南亚高压和超前3-12个月Ni o3指数之间高的显著正相关关系只是一个表象,并不是太平洋海温异常对南亚高压的直接影响结果,而是通过印度洋海盆模态的“充电/放电”作用引起的。

Based on observational data and ocean-atmosphere coupled model experiments, by analyzing the influence of the sea surface temperature （SST） anomaly main mode of the tropical Pacific ENSO and the Indian Ocean basin-wide mode （IOBM） on the South Asian High （SAH） in boreal summer, the ＂charge/ discharge＂ roles of the IOBM are revealed. Firstly, the SST anomaly in the mid-east equatorial of the Pacific charges to the Indian Ocean and induces the IOBM. Being the responding mode of the Pacific ENSO, the IOBM reaches its peak phase in the next spring of the ENSO developing year and can persist from the spring to the summer. Then, the warm （cool） SST anomaly of IOBM in the spring and the summer can in turn influence the atmospheric circulation and make SAH in summer stronger （weaker） through atmospheric response of ＂Matsuno-Gill pattern＂ and water vapor transportation anomaly by mean southwest wind of Asian summer monsoon circulation, this process is called ＂discharge＂. While the direct influence of the SST anomaly of the mid-east equatorial Pacific on SAH in summer is not significant, and it is pointed out that the high positive significant correlation between the SAH in summer and the leading 3 - 12 months Nino3 index is only a superficies, and not the result from the direct influence of the ENSO but from the ＂charge/discharge＂ role of the Indian Ocean.