Subseasonal-to-Seasonal Stratospheric Variability and Tropopause Polar Vortices
Variability in the high-latitude stratospheric flow can produce anomalous conditions near the tropopause that can persist on subseasonal-to-seasonal (S2S) timescales (two weeks to two months). These anomalous conditions can impact the evolution and dynamics of weather in the troposphere. This talk considers first considers the mechanisms by which the anomalous stratospheric flow can develop then examines the impacts of the anomalous stratospheric conditions on weather in the troposphere.
Since the anomalous stratospheric conditions linger near the tropopause, the tropospheric impacts are investigated by considering the duration, track, and amplitude of tropopause polar vortices (TPVs). TPVs are tropopause-based cyclonic features that can persist in the within the high-latitude regions for weeks. TPVs are known not only to be precursors to Arctic cyclones, but also to interact with the midlatitude jet stream and tropospheric Rossby wave trains, resulting in high-impact weather. Given the S2S timescales of both the TPV lifespan and high-latitude stratospheric variability, the interaction between the two phenomena is hypothesized to represent a pathway for extratropical variability on S2S timescales.
