Global SST influence on twentieth century NAO variability
Global SST influence on twentieth century NAO variability
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全球海温对二十世纪 NAO 变化的影响
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
A. Hense
中科院分区：
文献类型：
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作者：
H. Paeth;M. Latif;A. Hense
抽象的。
最近的研究表明，海表温度（SST）是北大西洋涛动（NAO）变率的一个重要来源。本文从四个方面对这一问题进行了研究：（1）研究了这一海洋影响的特征时间尺度，（2）根据SST驱动的大气环流模式（AGCM）集合，对20世纪北大西洋涛动的后报潜势进行了定量分析，并对北大西洋涛动的后报潜势与尺度的关系进行了研究。（3）识别相关海洋区域，定义了相应的SST指数，并利用互谱分析方法评价了它们与NAO的关系;我们的结果进行了比较与长期耦合控制实验与不同的海洋模式，以确保是否SST区域和NAO之间的光谱关系是一个内在的模式的耦合气候系统，涉及深海环流，而不是人为的单边SST强迫。观测到的NAO年际波动几乎不受SST的影响。在年代际时间尺度上，观测到的北大西洋涛动的主要波动被20世纪世纪中期以来的各种集合很好地再现，包括20世纪60年代的负状态和之后的部分正趋势。一个六人ECHAM 4-T42集合显示，SST边界条件影响整个世纪总的十年平均值和十年间趋势NAO变率的25%。与北大西洋涛动有关的最连贯的海温特征是著名的北大西洋三极。南太平洋和低纬度印度洋可能也有贡献。耦合气候模式控制运行表明，只有北大西洋SST-NAO关系是耦合气候系统的一个真正特征。观测和耦合模拟的相干性和相位谱非常一致，证实了这种十年尺度北大西洋海气耦合模式的鲁棒性。
Abstract.
Recent studies have suggested that sea surface temperature (SST) is an important source of variability of the North Atlantic Oscillation (NAO). Here, we deal with four basic aspects contributing to this issue: (1) we investigate the characteristic time scales of this oceanic influence; (2) quantify the scale-dependent hindcast potential of the NAO during the twentieth century as derived from SST-driven atmospheric general circulation model (AGCM) ensembles; (3) the relevant oceanic regions are identified, corresponding SST indices are defined and their relationship to the NAO are evaluated by means of cross spectral analysis and (4) our results are compared with long-term coupled control experiments with different ocean models in order to ensure whether the spectral relationship between the SST regions and the NAO is an intrinsic mode of the coupled climate system, involving the deep ocean circulation, rather than an artefact of the unilateral SST forcing. The observed year-to-year NAO fluctuations are barely influenced by the SST. On the decadal time scales the major swings of the observed NAO are well reproduced by various ensembles from the middle of the twentieth century onward, including the negative state in the 1960s and part of the positive trend afterwards. A six-member ECHAM4-T42 ensemble reveals that the SST boundary condition affects 25% of total decadal-mean and interdecadal-trend NAO variability throughout the twentieth century. The most coherent NAO-related SST feature is the well-known North Atlantic tripole. Additional contributions may arise from the southern Pacific and the low-latitude Indian Ocean. The coupled climate model control runs suggest only the North Atlantic SST-NAO relationship as being a true characteristic of the coupled climate system. The coherence and phase spectra of observations and coupled simulations are in excellent agreement, confirming the robustness of this decadal-scale North Atlantic air–sea coupled mode.