Severe weather influenced by aurorally excited gravity waves contributing to release of conditional symmetric instability?

Forecasting weather has significantly improved but continues to present challenges, such as prediction of flash floods, tornado outbreaks, and rapid intensification of tropical cyclones. We consider a possible influence on severe weather occurrence through solar wind coupling to the magnetosphere-ionosphere-atmosphere system, mediated by aurorally excited atmospheric gravity waves. Solar wind disturbances, including high-speed streams, high-density plasma adjacent to the heliospheric current sheet, and interplanetary coronal mass ejections, 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 are subject to amplification when encountering opposing winds and vertical wind shears. They may contribute to release of conditional symmetric instabilities [2] leading to slantwise convection, latent heat release and intensification of storms. The ERA5 re-analysis is used to evaluate slantwise convective available potential energy (SCAPE) that is of importance in the development of storms. It has been shown that significant weather events, including explosive extratropical cyclones [3,4], rapid intensification of tropical cyclones [5], and heavy rainfall causing floods and flash floods [6,7] tend to occur following arrivals of solar wind high-speed streams from coronal holes. Further evidence is provided by superposed-epoch analysis of high-rate precipitation occurrence obtained from satellite-based precipitation data sets. To support the published results, the occurrence of heavy-rainfall-induced floods and cool season precipitation events in Canada, as well as large tornado outbreaks in the United States are studied in the context of solar wind. 

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