Wind Variations in the Mesosphere and Lower Thermosphere Near 60°S Latitude During the 2019 Antarctic Sudden Stratospheric Warming

Abstract

Sudden stratospheric warmings (SSWs) could act as an important mediator in the vertical coupling of atmospheric regions and dramatic variations in the mesosphere and lower thermosphere (MLT) in response to SSWs have been documented. However, due to rare occurrences, SSWs in the Southern Hemisphere (SH) and their impacts on the MLT dynamics are not well understood. This study presents an analysis of MLT winds at similar to 80-98 km altitudes measured by meteor radars located at Tierra del Fuego (53.7 degrees S, 67.7 degrees W), King Edward Point (54.3 degrees S, 36.5 degrees W) and King Sejong Station (62.2 degrees S, 58.8 degrees W) near 60 degrees S latitude during the Antarctic winter. Eastward zonal winds from these stations are observed to decrease significantly near the peak date of the 2019 Antarctic SSW, and both zonal and meridional winds in 2019 exhibit considerable differences to the mean winds averaged over other non-SSW years. A quasi 6-day oscillation is observed at all three radar locations, being consistent with the presence of the westward propagating zonal wave-1 planetary wave. The vertical wavelength of this wave is estimated to be similar to 55 km, and the enhancement of the wave amplitude during this SSW is noticeable. Evidence of the interaction between the 6-day wave and the semidiurnal diurnal tide is provided, which suggests a possible mechanism for SSWs to impact the upper atmosphere. This study reports the large-scale variations in winds in the MLT region at SH midlatitudes to high latitudes in a key dynamic but largely unexplored latitudinal band in response to the 2019 Antarctic SSW.