The Life Cycle of the North Atlantic Storm Track
The Life Cycle of the North Atlantic Storm Track
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DOI：
10.1175/jas-d-14-0082.1
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发表时间：
2015-02-01
影响因子：
3.1
通讯作者：
Tailleux, Remi
中科院分区：
文献类型：
--
作者：
Novak, Lenka;Ambaum, Maarten H. P.;Tailleux, Remi
北大西洋涡旋驱动的急流表现出纬度的变化，有证据表明有三个首选的纬度位置：南、中、北。在这里，作者研究了这种可变性的驱动因素以及相关风暴路径的可变性。作者研究了这三个急流位置的风暴路径特征的变化，并提出了一种机制，通过这种机制，通过上游热通量测量的风暴路径活动的增强，是急流向下周期性纬向移动的原因。这一机制是基于经向温度梯度增强(从而斜压性)和经向高频(周期小于10天)涡旋热通量之间的非线性振子关系。斜压性和热通量的这种振荡导致涡旋各向异性的变化，这与主要的波破裂类型的变化和急流的不同纬度偏转有关。作者的结果表明，高热流有利于急流向北偏转，而低热流则有利于纬向急流。这种急流偏转效应被发现在风暴路径最大值的下游最显著，而风暴路径和急流仍然锚定在风暴路径开始时的固定纬度位置。风暴路径特征的这些周期性变化可以视为风暴路径时空生命周期的不同阶段。
The North Atlantic eddy-driven jet exhibits latitudinal variability with evidence of three preferred latitudinal locations: south, middle, and north. Here the authors examine the drivers of this variability and the variability of the associated storm track. The authors investigate the changes in the storm-track characteristics for the three jet locations and propose a mechanism by which enhanced storm-track activity, as measured by upstream heat flux, is responsible for cyclical downstream latitudinal shifts in the jet. This mechanism is based on a nonlinear oscillator relationship between the enhanced meridional temperature gradient (and thus baroclinicity) and the meridional high-frequency (periods of shorter than 10 days) eddy heat flux. Such oscillations in baroclinicity and heat flux induce variability in eddy anisotropy, which is associated with the changes in the dominant type of wave breaking and a different latitudinal deflection of the jet. The authors' results suggest that high heat flux is conducive to a northward deflection of the jet, whereas low heat flux is conducive to a more zonal jet. This jet-deflecting effect was found to operate most prominently downstream of the storm-track maximum, while the storm track and the jet remain anchored at a fixed latitudinal location at the beginning of the storm track. These cyclical changes in storm-track characteristics can be viewed as different stages of the storm track's spatiotemporal life cycle.