Analysis of the non-linearity in the pattern and time evolution of El Nio southern oscillation
Analysis of the non-linearity in the pattern and time evolution of El Nio southern oscillation
复制标题
DOI：
10.1007/s00382-012-1475-0
复制
发表时间：
2013-06-01
期刊：
影响因子：
4.6
通讯作者：
Frauen, Claudia
中科院分区：
文献类型：
--
作者：
Dommenget, Dietmar;Bayr, Tobias;Frauen, Claudia
本文分析了厄尔尼诺南方涛动（ENSO）事件空间分布和时间演变的非线性特征。结果表明，ENSO偏度不仅是事件振幅（厄尔尼诺强于拉尼娜）的一个特征，而且是事件空间分布和时间演变的一个特征。结果表明，这些非线性可能与纬向风对海表温度（SST）异常的非线性响应有关。观测资料和耦合模式模拟结果表明，正（El Nio）与负（La Nia）、强与弱事件在空间分布上存在显著差异，这主要反映了中太平洋与东太平洋事件的差异。中太平洋事件倾向于弱厄尔尼诺或强拉尼娜事件。反过来东太平洋事件往往是强厄尔尼诺或弱拉尼娜事件。两个主要的经验正交函数模式的旋转表明，厄尔尼诺和拉尼娜极端事件更可能比预期的正态分布。在观测和耦合模式模拟中，强厄尔尼诺/南方涛动事件的Bjerknes反馈和时间演变也显示出强烈的不对称性，强厄尔尼诺现象受纬向风的强迫比温跃层深度异常更强，其次是拉尼娜事件。反过来，强烈的拉尼娜事件之前，厄尔尼诺事件，更强烈地迫使温跃层深度异常比风异常。此外，强El Ni o事件期间纬向风对海温异常的响应较强，并相对于强La Ni a事件向东偏移，支持El Ni o事件的东移型和时间演变的不对称性。利用简化的混合耦合RECHOZ模式，分析了海温异常对纬向风场的非线性响应，结果表明，海温异常对ENSO事件的非对称强迫是造成ENSO事件的主要原因。这也意味着，强厄尔尼诺主要是风驱动的，可预测性较低，强拉尼娜主要是温跃层深度驱动的，可预测性较好，这是由一组100个完美的模型预测合奏证明。
In this study the observed non-linearity in the spatial pattern and time evolution of El Nio Southern Oscillation (ENSO) events is analyzed. It is shown that ENSO skewness is not only a characteristic of the amplitude of events (El Nios being stronger than La Nias) but also of the spatial pattern and time evolution. It is demonstrated that these non-linearities can be related to the non-linear response of the zonal winds to sea surface temperature (SST) anomalies. It is shown in observations as well as in coupled model simulations that significant differences in the spatial pattern between positive (El Nio) versus negative (La Nia) and strong versus weak events exist, which is mostly describing the difference between central and east Pacific events. Central Pacific events tend to be weak El Nio or strong La Nia events. In turn east Pacific events tend to be strong El Nio or weak La Nia events. A rotation of the two leading empirical orthogonal function modes illustrates that for both El Nio and La Nia extreme events are more likely than expected from a normal distribution. The Bjerknes feedbacks and time evolution of strong ENSO events in observations as well as in coupled model simulations also show strong asymmetries, with strong El Nios being forced more strongly by zonal wind than by thermocline depth anomalies and are followed by La Nia events. In turn strong La Nia events are preceded by El Nio events and are more strongly forced by thermocline depth anomalies than by wind anomalies. Further, the zonal wind response to sea surface temperature anomalies during strong El Nio events is stronger and shifted to the east relative to strong La Nia events, supporting the eastward shifted El Nio pattern and the asymmetric time evolution. Based on the simplified hybrid coupled RECHOZ model of ENSO it can be shown that the non-linear zonal wind response to SST anomalies causes the asymmetric forcings of ENSO events. This also implies that strong El Nios are mostly wind driven and less predictable and strong La Nias are mostly thermocline depth driven and better predictable, which is demonstrated by a set of 100 perfect model forecast ensembles.