Heavy Rainfall and Flash Floods Triggered by Aurorally Generated Atmospheric Gravity Waves?

Abstract:

Tropical and extratropical cyclones can lead to destructive weather causing heavy rainfall and flooding. Rapid intensification of such weather systems has been examined in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system. It has been shown [1,2] that explosive extratropical cyclones and rapid intensification of tropical cyclones tend to follow arrivals of high-speed solar wind. The coupling generates atmospheric gravity waves (AGWs) that propagate from the high-latitude lower thermosphere both upward and downward [3,4]. In the upper atmosphere, these AGWs are observed as traveling ionospheric disturbances. In the lower atmosphere, they can reach the troposphere and be ducted [4] to low latitudes. Despite significantly reduced wave amplitude, but subject to amplification upon over-reflection in the upper troposphere, these AGWs can trigger/release moist instabilities leading to convection and latent heat release, the energy driving the storms. The occurrence of severe weather, including severe winter storms, heavy snowfall and rainfall events, shows a tendency to follow arrivals of solar wind high-speed streams from coronal holes. In this presentation we provide further evidence to support these results. This includes heavy rainfall and flash floods, with the goal to identify sources of AGWs at high latitudes that may play a role in triggering such events.

[1] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 149, 219–231, 2016.

[2] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 183, 36–60, 2019.

[3] Prikryl P., et al., Ann. Geophys., 23, 401–417, 2005.

[4] Mayr H.G., et al., J. Geophys. Res., 89, 10929–10959, 1984.

[5] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 171, 94–110, 2018.