Abstract

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 which have lifetimes of longer than two weeks (the ninety-fifth 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 long-track 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. Notable differences emerge between the lifecycles of long-lived vortices in the summer and winter, specifically with regards to equatorward progression and amplitude. These long-lived TPVs also appear as likely as any TPV to exit the Arctic and move into the mid-latitudes, though this often occurs late in the vortex lifetime, immediately preceding vortex lysis in most cases.

Highlights

  • Tropopause polar vortices (TPVs) are a well-studied feature of the upper troposphere and lower stratosphere in high-latitude regions

  • Long-track TPVs show a 130 clear preference towards the summer, with a peak in occurrence in June and July. This trend is expected as summers will tend to have lower wind shear across the Arctic and fewer features propagating from the mid-latitudes that may disrupt radiative TPV strengthening

  • Though, the tails of each distribution extending into the mid-latitudes match up almost exactly, indicating that while long-track TPVs may spend a greater amount of their lifetime in the high Arctic, they are about as likely as any TPV to exit the Arctic eventually

Read more

Summary

Introduction

Tropopause polar vortices (TPVs) are a well-studied feature of the upper troposphere and lower stratosphere in high-latitude regions. Previous climatological studies of cyclonic PV anomalies near the tropopause (not necessarily using the TPV definition employed here) have found these vortices to be widespread across the Arctic, with especially high preference for regions over high terrain and near recurrent storm tracks (Hakim and Canavan, 2005; Kew et al, 2010; Cavallo and Hakim, 2009). Based on established characteristics of TPVs, these long track vortices are expected to form via dynamic processes and occur in especially low-shear environments (e.g., in the summer and in the high Arctic away from mid-latitude jets) These long-track TPVs are expected to possess behaviors somewhat different from an average TPV, they provide a more manageable case set through which to study the processes of vortex formation and movement. We hope that the results of this study will prove useful for improved physical knowledge and for forecasting applications in the future

Data and methods
Long-track TPV selection and statistical methods
Characteristics and spatial distributions of long-track TPVs
Long-track TPV genesis
Long-track TPV development and motion
Conclusions

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.