Investigating the Relationship between Tropopause Polar Vortices and Arctic Cyclone Longevity

Tropopause polar vortices (TPVs) are unique to polar regions partly because the colder environmental temperatures allow radiative processes to dominate over latent heating. The atmospheric flow in polar regions is furthermore characterized by vortices rather than waves that are favored in midlatitudes. TPVs are an important precursor to Arctic Cyclones (ACs), and they have radii up to ~1000 km and lifetimes of up to several months. Meanwhile, the processes that control the size and longevity of Arctic Cyclones (ACs) remain unclear, with some ACs reaching diameters of up to 5000 km and lifetimes sometimes over two weeks. The size and longevity of ACs are far larger than expected for balanced flows from theory based on the Rossby radius, where theory predicts smaller, subsynoptic-scale cyclones that are more consistent with polar lows. Given the significant role that TPVs have in the development and evolution of ACs, this study investigates the hypothesis that AC lifetimes can be extended due to multiple TPV interactions rather than just one single interaction.

ERA5 data is used with TPVTrack (TPV tracker) and Sprenger et al. 2017 (surface cyclone tracker) to match TPVs to ACs from 1979-2022. The longest-lived ACs are considered for the analysis (top 10^th percentile of lifetimes) in order to test the hypothesis on the longevity of ACs. Results show that as the number of TPV interactions with the Arctic Cyclone increase, the lifetimes of ACs tend to increase. Furthermore, there is no clear preferential direction for where a TPV may lie with respect to an Arctic Cyclone, supporting the notion that vortex-vortex interactions are a dominant process. Other results will be presented, showing statistical associations of TPVs with ACs, such as distance from AC, the strength of TPVs, and other TPV characteristics, which will motivate future directions of this research.