Equatorially Symmetric Impact of the El Nino-Southern Oscillation on the South Asian Summer Monsoon System
Equatorially Symmetric Impact of the El Nino-Southern Oscillation on the South Asian Summer Monsoon System
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DOI：
10.2151/jmsj.81.1329
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发表时间：
2003
影响因子：
3.1
通讯作者：
R. Kawamura;Tomonori Matsuura;S. Iizuka
中科院分区：
文献类型：
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作者：
R. Kawamura;Tomonori Matsuura;S. Iizuka
利用美国国家环境预报中心/美国国家大气研究中心再分析的海洋环流模式，确定了厄尔尼诺-南方涛动（ENSO）对南亚夏季风年际变率的主要影响。它有一个赤道对称的结构，并在20世纪60年代至70年代中期，当对流层两年期振荡（TBO）的ENSO占主导地位的ENSO在夏末的增长阶段最明显。随着ENSO的发展，热带印度洋和太平洋上空的一个异常步行者环流系统由夏季的单环流系统转变为秋季的双环流系统。与此同时，赤道对称结构的降水异常引起热带印度洋，伴随着南北孪生环流异常的对流层低层。北方环流与印度异常季风降水有着密切的动态联系，特别是在夏末。研究结果表明，印度洋风-蒸发反馈和热带太平洋海洋动力学的共同作用对与TBO型ENSO相关的异常步行者环流系统的体制转换至关重要。由于ENSO循环的季节性在70年代后期前后发生了变化，ENSO影响在其增长和衰减阶段的差异可能影响了ENSO-季风关系，并导致其年代际变化。
A dominant impact of the El Nino-Southern Oscillation (ENSO) on the South Asian summer monsoon interannual variability is identified using the National Centers for Environmental Prediction /National Center for Atmospheric Research reanalysis aided by an ocean general circulation model. It has an equatorially symmetric structure and is most pronounced at the growth phase of ENSO in late summer during the period from the 1960s to mid-1970s when tropospheric biennial oscillation (TBO)-like ENSO dominates. As ENSO develops, an anomalous Walker circulation system over the tropical Indian and Pacific oceans changes from a single-cell regime in summer to a double-cell regime in fall. Meanwhile, rainfall anomalies of an equatorially symmetric structure are induced over the tropical Indian Ocean, accompanied by north-south twin circulation anomalies in the lower troposphere. The northern circulation is dynamically linked with anomalous monsoon rainfall over India especially in late summer. This research suggests that a combination of the wind-evaporation feedback in the Indian Ocean and ocean dynamics in the tropical Pacific is crucial for the regime transition of the anomalous Walker circulation system associated with the TBO-like ENSO. As the seasonality of the ENSO cycle changes before and after the late 1970s, the difference in ENSO impacts between its growth and decay phases may have influenced the ENSO-monsoon relationship and caused its interdecadal change.