Characteristics of long-track tropopause polar vortices
Characteristics of long-track tropopause polar vortices
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DOI：
10.5194/wcd-3-251-2022
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发表时间：
2022-03-10
影响因子：
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通讯作者：
Cavallo, Steven M.
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文献类型：
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作者：
Bray, Matthew T.;Cavallo, Steven M.
对流层顶极涡（TPVs）是以对流层顶为中心形成并主要存在于高纬度地区的闭合环流。由于其伴随的气流，tpv已被证明会影响地面天气特征，因此，对这些特征的动力学的更深入了解可能会提高我们预测有影响的天气事件的能力。在本研究中，我们关注的是寿命超过2周的TPV子集（1979年至2018年期间所有TPV病例的第95百分位）；这些长寿命的涡旋为研究tpv增强的条件和分析涡旋形成和运动的模式提供了一个独特的机会。利用ERA-Interim数据，以及从同样的再分析中得到的TPV轨迹，我们研究了这些长寿命涡旋的形成、运动和发展。我们发现这些TPV明显更强，更经常发生在夏季，并且比平均TPV更倾向于保持两极。同样，这些TPVs显示在比平均水平更高的纬度形成。长寿命的tpv主要是通过从现有的涡旋中分裂而形成的，但也有少数人似乎是在没有现有tpv的情况下通过动态过程产生的。这些不太可能的分裂成因事件被发现发生在特定的地理区域，由罗斯比波的增长和破裂驱动。长寿命涡旋的生命周期出现季节性变化；值得注意的是，冬季tpv向赤道方向移动，通常振幅更强。这些长寿的热带气旋似乎也像任何热带气旋一样，有可能离开北极，进入中纬度地区，通过两条主要途径：通过加拿大或西伯利亚。
Tropopause polar vortices (TPVs) are closed circulations centered on the tropopause that form and predominately reside in high latitudes. Due to their attendant flow, TPVs have been shown to influence surface weather features, and thus, a greater understanding of the dynamics of these features may improve our ability to forecast impactful weather events. In this study, we focus on the subset of TPVs that have lifetimes of longer than 2 weeks (the 95th percentile of all TPV cases between 1979 and 2018); these long-lived vortices offer a unique opportunity to study the conditions under which TPVs strengthen and analyze patterns of vortex formation and movement. Using ERA-Interim data, along with TPV tracks derived from the same reanalysis, we investigate the formation, motion, and development of these long-lived vortices. We find that these TPVs are significantly stronger, occur more often in the summer, and tend to remain more poleward than an average TPV. Similarly, these TPVs are shown to form at higher latitudes than average. Long-lived TPVs form predominately by splitting from existing vortices, but a notable minority seem to generate via dynamic processes in the absence of pre-existing TPVs. These non-likely split genesis events are found to occur in select geographic regions, driven by Rossby wave growth and breaking. Seasonal variations emerge in the life cycles of long-lived vortices; notably, winter TPVs progress more equatorward and generally grow to stronger amplitudes. These long-lived TPVs also appear as likely as any TPV to exit the Arctic and move into the mid-latitudes, doing so via two primary pathways: through Canada or Siberia.