Linear interference and the Northern Annular Mode response to tropical SST forcing: Sensitivity to model configuration
Linear interference and the Northern Annular Mode response to tropical SST forcing: Sensitivity to model configuration
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DOI：
10.1002/jgrd.50385
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发表时间：
2013-05
期刊：
影响因子：
--
通讯作者：
C. Fletcher;P. Kushner
中科院分区：
文献类型：
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作者：
C. Fletcher;P. Kushner
与厄尔尼诺-南方涛动相关的热带海表温度（SST）的年际变化与北方环状模态（NAM）的遥相关有关。以往的研究表明，NAM对热带SST的响应的符号和振幅受进入副极地平流层的总波活动的控制，而这取决于行星波异常与气候定常波场的线性干扰。本研究使用多种配置的大气环流模式，以评估这些联系的鲁棒性的热带SST强迫和模式配置的细节。在23例与理想的SST强迫，热带和热带外波响应的振幅被发现与强迫强度近似线性缩放。但是，波振幅本身不足以预测NAM响应。相反，在所有情况下，波响应的空间结构（以及线性干扰）提供了NAM响应的最佳解释。即使在非线性贡献较强的情况下，线性干扰也解释了大部分的总波活动响应，这是由于准稳态波非线性和瞬态波引起的非线性之间的一致抵消。在这组有限的实验中，没有证据表明NAM对平流层水平分辨率或垂直分辨率的响应具有一致的敏感性。这些研究结果表明，线性干扰提供了一个强大的和可重复的机制，连接中纬度波响应纬向平均环流（NAM）的响应在各种各样的强迫情况下。
Interannual variability in tropical sea surface temperatures (SSTs) associated with the El Niño–Southern Oscillation is linked to teleconnections with the Northern Annular Mode (NAM). Previous work highlighted that the sign and amplitude of the NAM response to tropical SSTs are controlled by the total wave activity entering the subpolar stratosphere, which depends on the linear interference of planetary wave anomalies with the climatological stationary wave field. This study uses multiple configurations of atmospheric general circulation models to assess the robustness of these linkages to details of the tropical SST forcing and model configuration. Across 23 cases with idealized SST forcing, the amplitudes of the tropical and extratropical wave responses are found to scale approximately linearly with forcing strength. But wave amplitude alone is not sufficient to predict the NAM response. Instead, the spatial structure of the wave response (and hence the linear interference) provides the best explanation of the NAM response in all cases. Linear interference explains most of the total wave activity response even in cases with stronger nonlinear contributions, due to consistent cancellation between quasi‐stationary wave nonlinearity and nonlinearity arising from transient waves. Within this limited set of experiments, there is no evidence for a consistent sensitivity of the NAM response to horizontal resolution or to vertical resolution in the stratosphere. These findings reveal that linear interference provides a robust and reproducible mechanism linking midlatitude wave responses to zonal mean circulation (NAM) responses across a wide variety of forcing cases.