[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)

キーワード：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