Wind Variations in the Mesosphere and Lower Thermosphere Near 60°S Latitude During the 2019 Antarctic Sudden Stratospheric Warming. Issue 5 (7th May 2021)

• Record Type: Journal Article
• Authors: Liu, Guiping; Janches, Diego; Lieberman, Ruth S.; Moffat‐Griffin, Tracy; Mitchell, Nicholas J.; Kim, Jeong‐Han; Lee, Changsup
• Is Part Of: Journal of geophysical research. Volume 126:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-07
• Subjects: mesosphere and lower thermosphere -- mesospheric wind -- planetary wave -- planetary wave‐tide interaction -- tides -- upper atmosphere; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028909
• Languages: English
• ISSNs: 2169-9380

Abstract

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 ∼80–98 km altitudes measured by meteor radars located at Tierra del Fuego (53.7°S, 67.7°W), King Edward Point (54.3°S, 36.5°W) and King Sejong Station (62.2°S, 58.8°W) near 60°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 ∼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. Plain Language Summary: Sudden stratospheric warmings (SSWs) manifest dynamic disruptions in the polar winter stratosphere, characterized as rapid changes in temperature and wind within a few days. Although SSWs are by definition a stratospheric phenomenon, they have significant impacts throughout the middle and upper atmosphere. Many studies of the SSW impacts on the mesosphere and lower thermosphere (MLT) have been performed, mostly for the Northern Hemisphere (NH). In the Southern Hemisphere (SH), SSW events are rare and thus the Antarctic SSWs are not well known. An unusual SSW occurred in the SH during September 2019, and the work presented here focuses on studying the MLT winds observed by three meteor radars located at Tierra del Fuego (53.7°S, 67.7°W) in Argentina, King Edward Point (54.3°S, 36.5°W) on South Georgia Island, and King Sejong Station (62.2°S, 58.8°W) in King George Island. These observations are over a key dynamic but largely unexplored region around the Drake Passage. This study presents the large‐scale variations in the MLT winds at SH midlatitudes to high latitudes which are believed to be in response to the 2019 Antarctic SSW. Possible mechanisms for SSWs to impact the upper atmosphere are discussed. Key Points: Large wind disturbances are observed at ∼80–98 km altitude ∼60°S by three meteor radars during the 2019 Antarctic stratospheric warming A quasi 6‐day oscillation is observed at different longitudes indicating the presence of the westward propagating zonal wave‐1 wave This study provides observational evidence of the nonlinear interaction between the 6‐day planetary wave and the semidiurnal tide