Anticyclonic tropopause polar vortices and poleward-breaking Rossby waves

Tropopause polar vortices (TPVs) are sub-synoptic, long-lived, closed circulation features located in the upper-troposphere and lower-stratosphere (UTLS) region. The formation of TPVs is unique to polar regions, and due to the relatively limited role of latent heating, these features are generated by long wave radiative cooling. Although TPV circulations can be cyclonic or anticyclonic, most previous studies have focused on cyclonic TPVs due to their direct influence on surface weather features, including Arctic cyclones. Cyclonic TPVs also occur more numerously than their anticyclonic counterparts. However, any TPV may interact with the polar jet stream, and anticyclonic TPVs, in particular, can lead to synoptic-scale blocking patterns with potential implications on forecast skill on timescales ranging from medium range (up to 10-14 days) to sub-seasonal (weeks). This study characterizes anticyclonic TPVs with the hypothesis that anticyclonic TPVs can often form from a poleward-breaking Rossby wave originating in the midlatitudes.

Using ERA5 data from 1979-2019, a climatology of anticyclonic TPV tracks is created, and their basic properties are analyzed. A focus is placed on anticyclonic TPV genesis locations to determine whether these locations coincide with regions of known Rossby wave breaking, and their subsequent lifecycles are characterized. Results shed new information on the origins of anticyclonic TPVs and whether they exhibit preferred pathways between the Arctic and midlatitudes so that future predictability studies based on these features can be designed.