Does the North Atlantic Oscillation show unusual persistence on intraseasonal timescales?
Does the North Atlantic Oscillation show unusual persistence on intraseasonal timescales?
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DOI：
10.1029/2009gl040367
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发表时间：
2009-11-26
影响因子：
5.2
通讯作者：
Shaffrey, L. C.
中科院分区：
文献类型：
--
作者：
Keeley, S. P. E.;Sutton, R. T.;Shaffrey, L. C.
先前的研究认为，冬季北大西洋涛动（NAO）指数的自相关提供了异常持续的季节内动态的证据。我们证明，10-30 天的季节内时间尺度上的自相关对年际变化的存在很敏感，其中一部分来自季节内变化的采样，其余部分我们认为是“外部强迫”的。将 NAO 的季节内变率建模为红噪声过程，我们估计，对于冬季，类似 70% 的年际变率是外部强制的，而对于夏季采样则几乎解释了所有年际变率。校正外部强迫的年际变化对冬季的自相关函数有重大影响。当考虑外部强制年际变化时，NAO 的内在持续性在夏季和冬季非常相似（类似于 5 天）。这一发现对于理解 NAO 的动态具有重要意义。引用：Keeley, S. P. E.、R. T. Sutton 和 L. C. Shaffrey (2009)，北大西洋涛动在季节内时间尺度上是否表现出不寻常的持续性？，地球物理学。资源。快报，36，L22706，doi：10.1029/2009GL040367。
Previous studies have argued that the autocorrelation of the winter North Atlantic Oscillation (NAO) index provides evidence of unusually persistent intraseasonal dynamics. We demonstrate that the autocorrelation on intraseasonal time-scales of 10-30 days is sensitive to the presence of interannual variability, part of which arises from the sampling of intraseasonal variability and the remainder of which we consider to be "externally forced". Modelling the intraseasonal variability of the NAO as a red noise process we estimate, for winter, similar to 70% of the interannual variability is externally forced, whereas for summer sampling accounts for almost all of the interannual variability. Correcting for the externally forced interannual variability has a major impact on the autocorrelation function for winter. When externally forced interannual variability is taken into account the intrinsic persistence of the NAO is very similar in summer and winter (similar to 5 days). This finding has implications for understanding the dynamics of the NAO. Citation: Keeley, S. P. E., R. T. Sutton, and L. C. Shaffrey (2009), Does the North Atlantic Oscillation show unusual persistence on intraseasonal timescales?, Geophys. Res. Lett., 36, L22706, doi: 10.1029/2009GL040367.