Evolution of Indian Ocean dipole and its forcing mechanisms in the absence of ENSO
Evolution of Indian Ocean dipole and its forcing mechanisms in the absence of ENSO
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DOI：
10.1007/s00382-016-2977-y
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发表时间：
2016-01
期刊：
影响因子：
4.6
通讯作者：
Hui Wang;R. Murtugudde;Arun Kumar
中科院分区：
文献类型：
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作者：
Hui Wang;R. Murtugudde;Arun Kumar
通过对耦合模式模拟结果的分析，研究了印度洋偶极子（IOD）的演变及其强迫机制，分析了ENSO（厄尔尼诺-南方涛动）模式对印度洋偶极子的影响。即使没有ENSO，该模型也能再现IOD最显著的观测特征，包括东西两极在地表和次表层的关系，以及它们的季节性。这表明ENSO不是IOD存在的根本原因。它表明，冷（暖）海表面温度（SST）异常在东印度洋与IOD可以启动春季印尼降水不足（盈余）通过当地的地面风响应。SST异常的增长依赖于初始的局部次表层条件。海-气相互作用和地表-次表层相互作用对IOD的发展都有贡献。IOD的演变可以用两个主导的扩展经验正交函数（EEOF）模式来表示：一个是平稳的，另一个是非平稳的。IOD的开始、增长和终止，以及向相反相的转变，可以解释为非传播模式（EEOF 1）和向东传播的开尔文波（EEOF 2）之间的交替。IOD的演变也伴随着一个向西传播的Rossby波被捕获在EEOF 1的thessubtropicalsurf-subsurface印度洋温度。因此，Bjerknes反馈和一个延迟振荡器在IOD的演变过程中，在没有ENSO也。
The evolution of Indian Ocean dipole (IOD) and its forcing mechanisms are examined based on the analysis of coupled model simulations that allow or suppress the El Niño-Southern Oscillation (ENSO) mode of variability. The model can reproduce the most salient observed features of IOD even without ENSO, including the relationships between the eastern and western poles at both the surface and subsurface, as well as their seasonality. This suggests that ENSO is not fundamental for the existence of IOD. It is demonstrated that cold (warm) sea surface temperature (SST) anomalies in the eastern Indian Ocean associated with IOD can be initiated by springtime Indonesian rainfall deficit (surplus) through local surface wind response. The growth of the SST anomalies depends on the initial local subsurface condition. Both the air–sea interaction and surface–subsurface interaction contribute to the development of IOD. The evolution of IOD can be represented by two leading extended empirical orthogonal function (EEOF) modes oftropicalsurface–subsurface Indian Ocean temperatures; one stationary and the other non-stationary. The onset, growth, and termination of IOD, as well as the transition to an opposite phase, can be interpreted as alternations between the non-propagating mode (EEOF1) and the eastward-propagating Kelvin wave (EEOF2). The evolution of IOD is also accompanied by a westward-propagating Rossby wave which is captured in the EEOF1 of thesubtropicalsurface–subsurface Indian Ocean temperatures. Therefore, both Bjerknes feedback and a delayed oscillator operate during the evolution of IOD in the absence of ENSO also.