印度洋偶极子向海盆一致模转变的年代际变化及成因
投稿时间:2019-10-28  修订日期:2020-02-11  点此下载全文
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作者单位E-mail
郭品文 大气科学学院 guo@nuist.edu.cn 
吴清传 大气科学学院  
中文摘要:本文利用三种百年时间尺度的海温资料,探讨了21世纪印度洋偶极子(IOD)向海盆一致模(IOB)年际转变的年代际变化,结果发现在1940~1970期间几乎不存在这一转变现象,1970年以后则显著出现。研究表明,这种年代际变化是IOD与ENSO之间海气耦合作用出现年代际变化的结果,1940~1970年间IOD与ENSO之间发生发展相互独立,而1970年以后联系密切。通过进一步对物理量场的诊断分析,本文揭示了其中主要的动力机理:1970年以前,热带印度洋上空形成的季风环流异常无法与热带太平洋的反沃克环流进行耦合,IOD事件发生时无法与热带太平洋产生联系。反之,1970年以后,热带两大洋上空两个纬圈环流异常之间耦合作用强烈,正(负)IOD事件发生时,通过海气相互作用,促进正(负)El Ni?o的发生发展,印度洋又会受到来自ENSO的正反馈。因此这种“齿轮式”耦合模型能一直持续到冬季和次年春季,热带印度洋上空持续受到东(西)风异常的影响和低层环流的引导,西印度洋有次表层暖水的流入(出),加上印度洋本身海盆尺度较小,西边的暖(冷)水区显著增大,东西海温异常差异迅速减小并向海盆一致变暖(冷)转变,导致了后期冬季、春季正(负)IOB事件的出现。
中文关键词:印度洋偶极子(IOD)  印度洋单极子(IOB)  年际转变  年代际变化  ENSO
 
The Cause of the Interdecadal Variation of the Transition from the Indian Ocean Dipole to the Indian Ocean Basin Mode
Abstract:In this paper, the interdecadal variation of the interannual transition from Indian Ocean Dipole (IOD) to Indian Ocean Basin Mode (IOB) during the 21st century was investigated using three centennial SST datasets. The results shown that the transition is almost non-exist from 1940s to 1970s, and it appeared again after 1970s. And it was found that this interdecadal variation above is the result of the interdecadal variation of the air-sea coupling between IOD and ENSO during the same period. The occurrence and development of IOD and ENSO was independently from 1940s to 1970s, but after 1970s, the relationship between IOD and ENSO became close. Through further diagnostic analysis of the physical field, this paper reveals the main dynamic mechanism among. Before 1970s, the anomalous monsoon circulation over the tropical Indian Ocean could not be coupled with the anti-walker circulation over the tropical Pacific Ocean, the IOD event occurred when there was no connection to the tropical Pacific. On the contrary, after 1970s, the coupling is strong between the two latitudinal circulation anomalies over the two tropical oceans. When the positive(negative) IOD event occurs, the positive(negative) El Ni?o will be promoted through the air-sea interaction, and the positive feedback from ENSO will be received. Therefore, this "geared-like" coupled model could last until winter and the following spring, and the tropical Indian Ocean continues to be influenced by easterly(westerly) anomalies and low-level circulation. So there was an inflow(outflow) of subsurface warm water in western Indian Ocean, coupled with the small basin size of the Indian Ocean itself, the western warm(cold) water area increased significantly, and the difference between the east and west SST anomalies rapidly decreased and changed to a uniform warming(cold) of the basin, which led to the late winter and spring positive(negative) IOB events.
keywords:Indian Ocean Dipole (IOD)  Indian Ocean Basin Mode (IOB)  Interannual transition  Interdecadal variation  ENSO
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