Life cycles of tropopause polar vortices

Tropopause vortices are ubiquitous disturbances that play an active role in extratropical weather. Despite their abundance, particularly over polar latitudes, there remain a number of fundamental questions regarding their origin and dynamics. Over the arctic in particular, surface arctic cyclones are relatively better documented than are tropopause polar vortices (TPVs). Observations have shown that TPVs can drift from polar regions into jet stream regions enhancing the possibility of surface cyclogenesis. This study examines the life cycles of observed TPVs to gain a better understanding of the physical processes that govern their growth and decay. We first survey historical data to located regions with highest vortex genesis, and then use numerical model simulations to test a hypothesis that diabatic effects play a significant role in the structure and lifecycle of TPVs.

The observational aspect of this study reveals that the greatest genesis density of tropopause polar cyclones is found over northeastern Canada around the Baffin Island region, whereas for anticyclones the main genesis regions are found over central Greenland as well as in the Arctic Ocean just north of the Bering Straight. Simulations of individual cases were obtained using the Weather Research and Forecasting (WRF) model for cases of tropopause cyclones in order to examine the physical mechanisms affecting their intensity. Both the model simulations and observations reveal saturated conditions and light precipitation in the core of cyclonic vortices, despite the absence of surface cyclones. The affect of these diabatic affects on vortex intensity will be discussed.