A STUDY OFTHE INTERACTION BETWEEN THEASIAN SUMMER MONSOONAND EL NINO-SOUTHERN OSCILLATION

利用海洋环流模式（OGCM）和NCEP/NCAR再分析，我们得到了两个主要的影响（即，厄尔尼诺-南方涛动（ENSO）对南亚夏季风年际变化的影响。在印度洋和太平洋，类似热带涛动的厄尔尼诺/南方涛动现象占主导地位，在1960年代至1970年代中期，这种影响往往占主导地位。在热带印度洋上空，可以看到与ENSO发展有关的异常步行者环流的东移。与此相关的是，在夏末印度洋西部和东部之间的纬向非对称SST异常的突出。从夏季到秋季，印度洋上空的赤道低层孪生环流异常与印度的季风降水异常有着密切的联系，尤其是在夏末，印度洋上空的北方孪生环流与印度的季风降水异常有着密切的联系。如果类似TBO的ENSO体制具有精确的两年周期， 关于我们 相反，EA的影响需要延长ENSO，不终止于北方春季，因为持续异常对流加热在菲律宾附近的前一个冬天到晚春触发WES反馈制度在印度洋。由于长期冷暖事件的频繁发生，70年代后期以后，ENSO衰减阶段的EA影响变得显著。在20世纪70年代后期之前，ENSO增长阶段的环境影响导致了ENSO与季风的强烈耦合，而在20世纪70年代后期之后，延长的ENSO的发生导致了ENSO衰减阶段的环境影响，这种影响在季风季节的早期阶段是显著的。与ES的影响相比，EA的影响是间接的，并且不会持续到夏末。70年代后期以后的季风往往同时经历ENSO的ES和EA影响，但ES影响变得不那么明显。我们的结论是，这些功能导致的ENSO季风关系的下降后，20世纪70年代末。少

Using an ocean general circulation model (OGCM) and NCEP/NCAR reanalysis, we obtained two major impacts (i.e., ES and EA impacts) of El Nino-Southern Oscillation (ENSO) on the South Asian summer monsoon interannual variability. The ES impact, which is dominated by TBO-like ENSO in the Indian Ocean and the Pacific Ocean, tends to prevail during the period from the 1960s to mid-1970s. Eastward migration of anomalous Walker circulation relevant to the growth of ENSO can be seen over the tropical Indian Ocean. Associated with this is the prominence of zonally asymmetric SST anomalies between the western and eastern parts of the Indian Ocean in late summer. Low-level twins anomalous circulation across the equator is induced over the Indian Ocean from summer to fall and its northern counterpart is dynamically linked with anomalous monsoon rainfall over India especially in late summer. If the TBO-like ENSO regime has a precise biennial periodicity, the summer monsoon season always corresponds … More to the growth phase of ENSO, which means that the monsoon is always affected by the ES impact.By contrast, the EA impact requires the prolonged ENSO that does not terminate in boreal spring because persistent anomalous convective heating in the vicinity of the Philippines from the preceding winter to late spring triggers a WES feedback regime in the Indian Ocean. Due to the frequent occurrence of the prolonged warm and cold events, the EA impact at the decay phase of ENSO becomes significant after the late 1970s. The ES impact at the growth phase of TBO-like ENSO brings about the strong ENSO-monsoon coupling prior to the late 1970s, while the occurrence of the prolonged ENSO after the late 1970s induces the EA impact on the monsoon at the decay phase of ENSO that is significant at the early stage of the monsoon season. Compared to the ES impact, the EA impact is indirect and not persistent until late summer. Furthermore, the monsoon after the late 1970s tends to experience both the ES and EA impacts of ENSO although the ES impact becomes less clear. We conclude that these features lead to the decline of the ENSO-monsoon relationship after the late 1970s. Less