November 3, 2021 - 3:00 pm
November 3, 2021 - 4:00 pm
CategoriesWeather and Climate Systems
Weather and Climate Systems
Characteristics and Lifecycles of Northern Hemisphere Anticyclonic Tropopause Polar Vortices
Wednesday, November 3
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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 maintained by longwave radiative cooling. Although TPV circulations can be cyclonic or anticyclonic, most previous studies have focused on cyclonic TPVs and their contributions to Arctic cyclogenesis. More recent studies have illustrated the role of cyclonic TPVs in triggering extreme weather events (i.e., cold air outbreaks, severe convection) in middle latitudes. However, any TPV may interact with the polar jet stream, and anticyclonic TPVs in particular can lead to synoptic-scale blocking patterns. This study characterizes anticyclonic TPVs with the hypothesis that anticyclonic TPVs can often form from poleward-breaking Rossby waves and are related to blocking patterns in the midlatitudes. Since the onset of blocking events are often poorly predicted in global models, a motivation for this study is that advancing knowledge of the interaction between anticyclonic TPVs and the jet stream has the potential to benefit forecast skill on timescales ranging from medium range (up to 10-14 days) to subseasonal (weeks). Another motivation for this study is that Rossby wave breaking has been linked to extreme precipitation events. Using ERA5 data from 1980-2009 a climatology of Northern Hemisphere anticyclonic TPV tracks is compiled, allowing their basic properties to be analyzed. A focus is placed on anticyclonic TPV motion and track length, as well as their lifecycle. Results shed new information on the origins and movement 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.