Tropical Pacific decadal variability and ENSO amplitude modulation in a CGCM
Tropical Pacific decadal variability and ENSO amplitude modulation in a CGCM
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DOI：
10.1029/2004jc002442
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发表时间：
2004-11
影响因子：
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通讯作者：
S. Yeh;B. Kirtman
中科院分区：
文献类型：
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作者：
S. Yeh;B. Kirtman
[1]利用一个耦合大气环流模式(CGCM)的三个运行，研究了热带太平洋平均状态的年代际变化与厄尔尼诺-南方涛动(ENSO)年代际调制之间的联系。三种模式之间的差异，即标准耦合模式(一个AGCM耦合到一个OGCM)和两个交互集合模式(六个或十二个AGCM耦合到一个OGCM)之间的差异仅限于内部大气变率的幅度。这三个模拟都具有相同的热带太平洋盆地尺度SST模式，该模式主导着低频变化，这是由第一个EOF模式识别的。这种低频模式在很大程度上独立于模拟的ENSO，既不是十年制ENSO调制的残余物，也不产生任何ENSO的低频调制。这里的分析表明，这种低频模式是由大气噪声随机驱动的。然而，热带太平洋平均状态存在与ENSO年代际调制有关的低频变化。与ENSO振幅相关的平均状态在海温和风应力异常中具有不同的结构，与第一个EOF所确定的热带太平洋平均状态不同。热带太平洋平均状态，明确地与ENSO年代际调制有关，在两个相互作用的集合模式中与第二个EOF SST模非常相似，但在标准耦合模式模拟中很难检测到。这些结果表明，ENSO变率中有一个分量不能用线性、阻尼性和随机强迫过程来解释。
[1] Connections between decadal changes in the tropical Pacific mean state and El Nino–Southern Oscillation (ENSO) decadal modulation are examined using three runs of a coupled general circulation model (CGCM). The differences between the three simulations, i.e., a standard coupled model (one AGCM is coupled to a single OGCM) and two interactive ensemble models (six or twelve AGCMs are coupled to a single OGCM), are confined to the amplitude of internal atmospheric variability. All three simulations have the same tropical Pacific basin scale SST mode that dominates the low-frequency variability, which is identified by the first EOF mode. This low-frequency mode is largely independent of the simulated ENSO and is neither a residual of the decadal ENSO modulation nor does it produce any low-frequency modulation of ENSO. The analysis presented here suggests that this low-frequency mode is stochastically driven by atmosphere noise. There are, however, low-frequency changes in the tropical Pacific mean state that are connected to ENSO decadal modulation. The mean state associated with ENSO amplitude has different structures in the SST and wind stress anomalies than does the dominant tropical Pacific mean state identified by the first EOF. The tropical Pacific mean state that is unambiguously associated with ENSO decadal modulation, which is remarkably similar to the second EOF SST mode in two interactive ensemble models, but is difficult to detect in a standard coupled model simulation. These results argue that there is a component of ENSO variability that cannot be explained by a linear, damped and stochastically forced process.