Dynamical Response of the Middle and Upper Atmosphere to the February 2018 Sudden Stratospheric Warming Revealed by MERRA-2 and SABER

Abstract

The middle and upper atmosphere plays a critical role in linking the lower atmosphere forcing with ionospheric variability, especially during strong atmospheric activities. This study examines the dynamical response in the altitude range from ∼20 to 80 km to a major Sudden Stratospheric Warming (SSW) event peaking on 11 February 2018. We compare the reanalysis product of the Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) from the Goddard Earth Observing System (GEOS) to the satellite observations by Thermosphere Ionosphere and Mesosphere Electric Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) TIMED/SABER that are not assimilated in MERRA-2. Our study shows that the zonal mean wind and temperature and planetary wave 1 and 2 variations are generally consistent between the reanalysis and observations. We also identify a strong ∼6 day wave propagating both westward and eastward with zonal wavenumber-1 with the westward propagating component likely generated by baroclinic/barotropic instability. However, important disagreements arise specifically above ∼60 km, where the wind and temperature are not well represented in MERRA-2, causing differences in the day-to-day development of 6 day wave. This study highlights the need for additional assimilation of mesospheric data and development of high-altitude vertically extended GEOS model.