The Importance of Past MJO Activity in Determining the Future State of the Midlatitude Circulation
The Importance of Past MJO Activity in Determining the Future State of the Midlatitude Circulation
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DOI：
10.1175/jcli-d-19-0512.1
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发表时间：
2020-02
影响因子：
4.9
通讯作者：
Kai‐Chih Tseng;E. Barnes;E. Maloney
中科院分区：
文献类型：
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作者：
Kai‐Chih Tseng;E. Barnes;E. Maloney
Madden-Julian振荡(MJO)是从亚季节到季节(S2S)时间尺度上最重要的可预报性来源之一。许多以前的研究探索了MJO的现状对温带天气模式的未来演变和可预报性的影响。然而，尚不清楚的是，过去MJO活动对这些结果的累积影响的重要性。在这项研究中，利用线性斜压模型(LBM)和最简单的机器学习算法之一：Logistic回归，研究了过去MJO活动在确定未来温带环流状态中的重要性。通过增加关于MJO过去活动的附加信息来增加Logistic回归模型的复杂性，证明了过去15天在决定未来15天以后MJO遥相关状态方面起主导作用。这一结论得到了LBM数值模拟的支持。它进一步表明，过去15天的额外信息只对某些MJO阶段/交货期重要，而对其他阶段不重要，并探讨了这一结果的物理基础。
The Madden–Julian oscillation (MJO) is one of the most important sources of predictability on subseasonal to seasonal (S2S) time scales. Many previous studies have explored the impact of the present state of the MJO on the future evolution and predictability of extratropical weather patterns. What is still unclear, however, is the importance of the accumulated influence of past MJO activity on these results. In this study, the importance of past MJO activity in determining the future state of extratropical circulations is examined by using a linear baroclinic model (LBM) and one of the simplest machine learning algorithms: logistic regression. By increasing the complexity of the logistic regression model with additional information about the past activity of the MJO, it is demonstrated that the past 15 days play a dominant role in determining the state of MJO teleconnections more than 15 days into the future. This conclusion is supported by numerical LBM simulations. It is further shown that the past 15 days of additional information are only important for some MJO phases/lead times and not others, and the physical basis for this result is explored.