ENSO in the Mid-Holocene according to CSM and HadCM3
ENSO in the Mid-Holocene according to CSM and HadCM3
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DOI：
10.1175/jcli-d-13-00251.1
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发表时间：
2014-01
影响因子：
4.9
通讯作者：
W. Roberts;D. Battisti;A. Tudhope
中科院分区：
文献类型：
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作者：
W. Roberts;D. Battisti;A. Tudhope
离线线性化海洋大气模式（LOAM）是为了量化气候平均状态对厄尔尼诺振荡（ENSO）变率的影响而开发的，它被用来解释在使用NCAR气候系统模式（CSM）和Hadley中心耦合模式第三版（HadCM 3）的两个气候模拟研究中，ENSO在现代和全新世早期/中期之间变化的原因。LOAM再现了气候模式模拟的时空变率，并显示了ENSO方差的减少和方差空间结构的变化，在早/中全新世期间，每个模式中重要的平均状态变化是不同的，在这两种情况下，也不同于描述这些模拟的原始论文中假设的重要变化。在CSM模拟中，ENSO模是由SST的平均冷却来稳定的。这减少了大气加热异常，反过来又使风应力异常变小，从而削弱了Bjerknes反馈。在海洋内部，温跃层结构的变化改变了方差的空间格局，使峰值方差向东移动，但并没有减少ENSO方差的总体幅度。在HadCM 3中，ENSO模态是由较弱的温跃层和减弱的水平表面流的组合稳定的。这两种方法都通过减少海洋对风应力强迫的SST响应来减少Bjerknes反馈。这项研究表明了考虑平均状态变化对耦合海洋-大气系统的综合影响的重要性：如果只考虑一个模型组件，则两个模型都会得到相互矛盾和错误的结果。
The offline linearized ocean‐atmosphere model (LOAM), which was developed to quantify the impact of the climatological mean state on the variability of the El Ni~ Oscillation (ENSO), is used to illuminate why ENSO changed between the modern-day and early/mid-Holocene simulations in two climate modeling studies using the NCAR Climate System Model (CSM) and the Hadley Centre Coupled Model, version 3 (HadCM3). LOAM reproduces the spatiotemporal variability simulated by the climate models and shows both the reduction in the variance of ENSO and the changes in the spatial structure of the variance duringtheearly/mid-Holocene.Themeanstatechangesthatareimportantin eachmodel aredifferentand,in both cases, are also different from those hypothesized to be important in the original papers describing these simulations. In the CSM simulations, the ENSO mode is stabilized by the mean cooling of the SST. This reduces atmospheric heating anomalies that in turn give smaller wind stress anomalies, thus weakening the Bjerknes feedback. Within the ocean, a change in the thermocline structure alters the spatial pattern of the variance,shiftingthepeakvariancefarthereast,but doesnot reducetheoverallamountofENSOvariance.In HadCM3, the ENSO mode is stabilized by a combination of a weaker thermocline and weakened horizontal surface currents. Both of these reduce the Bjerknes feedback by reducing the ocean’s SST response to wind stress forcing. This study demonstrates the importance of considering the combined effect of a mean state change on the coupled ocean‐atmosphere system: conflicting and erroneous results are obtained for both models if only one model component is considered in isolation.