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INTERDECADAL MODULATION OF TROPICAL BIENNIAL OSCILLATION AND EL NINO-SOUTHERN OSCILLATION

热带两年期振荡和厄尔尼诺-南方涛动的年代际调制

基本信息

批准号：
14540406
负责人：
KAWAMURA Ryuichi
金额：
$ 2.05万
依托单位：
TOYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540406/
关键词：
BIENNIAL OSCILLATION ENSO ELNINO ONSOON

项目摘要

A dominant impact of 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. In the meantime, 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. It is suggested 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 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.

利用国家环境预测中心/国家大气研究中心在海洋环流模式辅助下的再分析，确定了厄尔尼诺-南方涛动（ENSO）对南亚夏季风年际变化的主要影响。它具有赤道对称结构，在20世纪60年代至70年代中期ENSO的夏末生长期最为明显，而对流层双年振荡（TBO）型ENSO占主导地位。随着ENSO的发展，热带印度洋和太平洋上空的异常沃克环流系统从夏季的单细胞状态转变为秋季的双细胞状态。与此同时，热带印度洋上空出现赤道对称结构的降水异常，对流层下层出现南北双环流异常。特别是在夏末，北部环流与印度的异常季风性降雨有动态联系。印度洋风蒸发反馈和热带太平洋海洋动力的结合对与tbo样ENSO相关的异常Walker环流系统的状态转变至关重要。由于70年代末前后ENSO周期的季节性变化，ENSO增长期和衰减期影响的差异可能影响了ENSO-季风关系并导致其年代际变化。