Direct Observational Evidence of Altered Mesosphere Lower Thermosphere Mean Circulation From a Major Sudden Stratospheric Warming
Federico Gasperini, McArthur Jones, Brian J. Harding, T. J. Immel
Abstract
Abstract Sudden stratospheric warmings (SSWs) are large‐scale phenomena characterized by dramatic dynamic disruptions in the stratospheric winter polar regions. Previous studies, especially those employing whole atmosphere models, indicate that SSWs have strong impacts on the circulation of the mesosphere lower thermosphere (MLT) and drive a reversal in the mean meridional circulation (MMC) near 90–125 km altitude. However, the robustness of these effects and the roles of SSW‐induced changes in global‐scale wave activity to drive the reversal have been difficult to observe simultaneously. This work employs horizontal lower thermospheric (∼93–106 km altitude) winds near 10°S‐40°N latitude from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging instrument onboard the Ionospheric Connection Explorer (ICON) to present observational evidence of a prominent MLT MMC reversal associated with the January 2021 major SSW event and to demonstrate connections to semidiurnal tidal activity and possible associations with a ∼3‐day ultra‐fast Kevin wave.