Utilizing three different sets of reanalysis data, this study examines the long- and short-lived observed positive North Atlantic Oscillation (NAO) events (referred to as NAO+_LE and NAO+_SE) and long- and short-lived observed negative NAO events (referred to as NAO−_LE and NAO−_SE). Composite results indicate that the NAO-like circulation anomalies associated with the long-lived NAO events can reach the stratosphere, while they are primarily confined to the troposphere in the short-lived NAO events. Thus, the coupling/connection of stratospheric and tropospheric circulation anomalies is much better (worse) in the long-lived (short-lived) NAO events. A series of modified stratospheric initial-value experiments conducted with a simplified model indicate that a better (worse) connection between stratospheric and tropospheric circulation anomalies in the initial-value fields tend to gradually induce the NAO-like tropospheric circulation anomalies in the troposphere on the subsequent days, and thus naturally elongate (reduce) the lifetimes of the original NAO events by altering the tropospheric synoptic eddy vorticity flux over the North Atlantic region.

中文翻译：

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观测到的长期和短期北大西洋振荡事件：平流层的作用

本研究利用三组不同的再分析数据，检查了长期和短期观察到的北大西洋涛动 (NAO) 正事件（称为 NAO+_LE 和 NAO+_SE）以及长期和短期观察到的负 NAO 事件（称为 NAO-_LE 和 NAO-_SE）。综合结果表明，与长寿命 NAO 事件相关的类 NAO 环流异常可以到达平流层，而在短寿命 NAO 事件中它们主要局限于对流层。因此，在长寿命（短寿命）NAO 事件中，平流层和对流层环流异常的耦合/连接要好得多（更糟）。