东亚夏季风的年际到年代际变化及其与全球大气环流和海表温度的联系

摘要

The East Asian summer monsoon (EASM) underwent an interdecadal variation with interannual variations during the period from 1958 to 1997, its index tended to decline from a higher stage in the mid-1960＇s until it reached a lower stage after 1980＇s. Correlation analysis reveals that EASM is closely related with the global atmospheric circulation and sea surface temperature (SST). The differences between the weak and strong stage of EASM shows that, the summer monsoon circulation over East Asia and North Africa is sharply weakened, in the meantime, the westerlies in high latitudes and the trade--wind over the tropical ocean are also changed significantly. Over the most regions south of the northern subtropics, both air temperature in the lower troposphere and SST tended to rise compared with the strong stage of EASM. It is also revealed that the ocean-atmosphere interaction over the western Pacific and Indian Ocean plays a key role in interannual to interdecadal variation of EASM, most probably, the subtropical Indian Ocean is more important. On the other hand, the ENSO event is less related to EASM at least during the concerned period.%伴随着年际变化过程，东亚夏季风在1958年到1997年期间经历了一次年代际变化，其指数从60年代中期的高值期持续下降，80年代之后达到低值期。相关分析显示东亚夏季风与全球大气环流和海表温度有密切关系。东亚夏季风弱与强时期之差表明，东亚和非夏季风环流有很大减弱，同时，高纬西风带和热带海洋上的信风也有很大变化。在北半球副热带以南的大部分地区，对流层低层气温和海表温度均有升高趋势。研究结果还表明，西太平洋和印度洋地区的海气相互作用对东亚夏季风的年际到年代际变化起到关键作用，并且，副热带印度洋有可能更重要。但至少在上述时间尺度上，ENSO事件似乎与东亚夏季风关系不大。