Sudden Stratospheric Warmings and Anomalous Upward Wave Activity Flux
Sudden Stratospheric Warmings and Anomalous Upward Wave Activity Flux
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DOI：
10.2151/sola.13a-002
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发表时间：
2017-01-01
期刊：
影响因子：
1.9
通讯作者：
Albers, John R.
中科院分区：
文献类型：
--
作者：
Birner, Thomas;Albers, John R.
极地冬季平流层环流的突然崩溃，比如平流层突然增温（SSWs），是向上传播的行星波与平均气流之间强烈双向相互作用的一种表现。长期以来，人们已经认识到来自对流层足够的向上波活动通量以及平流层环流之前的状态在引发类似平流层突然增温事件中的重要性。过去基于理想化数值模拟的研究表明，在产生极端平流层事件方面，平流层的状态可能比来自对流层的异常向上波通量更为重要。其他研究则强调了对流层先兆事件的作用。在此，再分析数据被用于定义平流层平均气流极端减速事件（平流层突然增温是其中一部分）以及对流层下部向上行星波活动通量极端事件。尽管导致类似平流层突然增温事件的波通量最终源于地表附近，但与这些事件相关的异常向上波活动通量主要出现在平流层内。引发类似平流层突然增温事件的关键动力学似乎发生在对流层顶上方的过渡层。来自对流层下部的异常向上波通量可能在某些事件中起作用，但对于大多数事件来说似乎不太重要。
Abrupt breakdowns of the polar winter stratospheric circulation such as sudden stratospheric warmings (SSWs) are a manifestation of strong two-way interactions between upward propagating planetary waves and the mean flow. The importance of sufficient upward wave activity fluxes from the troposphere and the preceding state of the stratospheric circulation in forcing SSW-like events have long been recognized. Past research based on idealized numerical simulations has suggested that the state of the stratosphere may be more important in generating extreme stratospheric events than anomalous upward wave fluxes from the troposphere. Other studies have emphasized the role of tropospheric precursor events. Here reanalysis data are used to define events of extreme stratospheric mean flow deceleration (SSWs being a subset) and events of extreme lower tropospheric upward planetary wave activity flux. While the wave fluxes leading to SSW-like events ultimately originate near the surface, the anomalous upward wave activity fluxes associated with these events primarily occur within the stratosphere. The crucial dynamics for forcing SSW-like events appear to take place in the communication layer just above the tropopause. Anomalous upward wave fluxes from the lower troposphere may play a role for some events, but seem less important for the majority of them.