Causes of the El Niño and La Niña Amplitude Asymmetry in the Equatorial Eastern Pacific
Causes of the El Niño and La Niña Amplitude Asymmetry in the Equatorial Eastern Pacific
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DOI：
10.1175/2009jcli2894.1
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发表时间：
2010-02
影响因子：
4.9
通讯作者：
Jingzhi Su;Renhe Zhang;Tim Li;X. Rong;J. Kug;C. Hong
中科院分区：
文献类型：
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作者：
Jingzhi Su;Renhe Zhang;Tim Li;X. Rong;J. Kug;C. Hong
利用三种海洋同化产品：简单海洋数据同化(SODA)2.0.2、SODA 1.4.2和全球海洋数据同化系统(GODAS)诊断ENSO发展阶段的混合层热量收支，研究了厄尔尼诺和拉尼娜之间的幅度不对称性。结果表明，纬向和经向海温的非线性平流是造成远东太平洋海温不对称性的主要因素，而垂直非线性平流的作用则相反。纬向流异常以地转流为主，伴随着温跃层深度的变化。经向流异常主要是由风应力驱动的Ekman流引起的。由此产生的异常水平流导致厄尔尼诺和拉尼娜事件期间的暖非线性平流，从而增强(减弱)厄尔尼诺(拉尼娜)的幅度。在此过程中，异常地转混合层流的辐合(散度)也发生了变化。
Abstract The amplitude asymmetry between El Nino and La Nina is investigated by diagnosing the mixed-layer heat budget during the ENSO developing phase by using the three ocean assimilation products: Simple Ocean Data Assimilation (SODA) 2.0.2, SODA 1.4.2, and the Global Ocean Data Assimilation System (GODAS). It is found that the nonlinear zonal and meridional ocean temperature advections are essential to cause the asymmetry in the far eastern Pacific, whereas the vertical nonlinear advection has the opposite effect. The zonal current anomaly is dominated by the geostrophic current in association with the thermocline depth variation. The meridional current anomaly is primarily attributed to the Ekman current driven by wind stress forcing. The resulting induced anomalous horizontal currents lead to warm nonlinear advection during both El Nino and La Nina episodes and thus strengthen (weaken) the El Nino (La Nina) amplitude. The convergence (divergence) of the anomalous geostrophic mixed-layer currents dur...