[A-AS04] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS04-P02] Auroral Gravity Waves Contributing to Conditional Symmetric Instability Release and Severe Mesoscale Weather

*Paul Prikryl¹, Vojto Rušin² (1.Physics Department University of New Brunswick, 2.Astronomical Institute, Slovak Academy of Sciences)

Keywords:Conditional symmetric instability, Winter storms, Flash floods, Auroral atmospheric gravity waves, Solar wind

We consider possible influence on severe mesoscale weather occurrence by solar wind coupling to the magnetosphere-ionosphere-atmosphere system, mediated by aurorally generated atmospheric gravity waves. Solar wind high-speed streams from coronal holes cause intensifications of ionospheric currents at high latitudes launching gravity waves globally propagating in the atmosphere [1]. While these gravity waves reach the troposphere with much attenuated amplitudes, they can contribute to conditional symmetric instability release [2], leading to slantwise convection and intensification of storms [3]. The ERA5 re-analysis is used to evaluate slantwise convective available potential energy (SCAPE) to assess the likelihood of slantwise convection in frontal zones of extratropical cyclones. The low-level southerly winds and high wind shears in these regions are favourable conditions for over-reflection of gravity waves from auroral sources. It is observed that severe weather events, including winter storms, heavy rainfall, and flash floods, tend to follow arrivals of solar wind high-speed streams.

[1] Mayr H.G., et al., Space Sci. Rev. 54, 297–375, 1990. doi:10.1007/BF00177800
[2] Chen T.-C., et al., J. Atmos. Sci. 75, 2425–2443. doi:10.1175/JAS-D-17-0221.1
[3] Prikryl P. & Rušin V., Front. Astron. Space Sci. 10, 2023. doi.org/10.3389/fspas.2023.1196231