| Summary: | Tropopause polar vortices (TPVs) are coherent, closed tropopause-based vortices that spend at least 60% of their lifetime poleward of 65° latitude. TPVs are identified by a local minima in potential temperature and height, and a local maxima in potential vorticity on the dynamic tropopause. TPVs are most common in the Arctic, where they are often associated with the intensification of Arctic cyclones (ACs), but on occasion exit the Arctic into the midlatitudes where they are often associated with cold air outbreaks (CAOs). This dissertation investigates TPV linkages to ACs, CAOs, and polar lows (PLs), focusing on systematic TPV-AC linkages and case studies of TPV intensity linkages to an AC case, a PL case, and a major CAO. Rapidly deepening ACs are commonly associated with an upstream TPV which becomes vertically aligned with the AC by the end of the rapid deepening episode. Summer cases are associated with closer proximity to the closest TPV and less lower-tropospheric baroclinic instability than winter cases, with summer cases often over the central Arctic Ocean and winter cases often in the North Atlantic into the Barents and Kara seas. Additionally, ACs whose rapid deepening episode coincides with cyclogenesis are less likely to be over the central Arctic Ocean and are farther from the closest TPV relative to ACs that develop at least 24 h prior to the onset of rapid deepening. Numerical simulations designed to modify the intensity of two TPVs associated with the August 2012 ``Great Arctic Cyclone" show that stronger TPVs are associated with a faster peak deepening rate and earlier peak intensity of the cyclone, but with the closer TPV to the AC exhibiting a greater impact on the intensification rate of the AC, and the farther TPV exhibiting a greater impact on the track of the AC. The increased intensification rate is primarily associated with stronger differential cyclonic vorticity advection downstream of the TPVs. Weakening the broader upper-tropospheric trough within which the closer TPV is embedded in ...
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