Matthew Bray- December 1

Weather and Climate Systems

Characteristics of Long-track Tropopause Polar Vortices

Matthew Bray

Wednesday, December 1

3:00 PM

Join Google Meet:

https://meet.google.com/joz-jnzu-cgr

Tropopause polar vortices (TPVs) are closed, cyclonic circulations centered on the tropopause that form and mostly reside in high latitudes. TPVs have been shown to influence surface features, and so a greater understanding of their governing processes 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 as these long-lived vortices offer a unique opportunity to study the conditions under which TPVs strengthen and examine their evolution over time. 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 long-track TPVs are stronger, more likely to occur in the summer, and generally located more poleward than an average TPV. Long-lived TPVs form predominately by splitting from existing vortices, but a notable minority generate via Rossby wave growth and breaking in the absence of pre-existing TPVs. Seasonal differences emerge in the lifecycles of long-lived vortices, specifically with regard to equatorward progression and amplitude. Long-lived TPVs also appear as likely as any TPV to exit the Arctic and move into the mid-latitudes, following one of two major exit pathways.