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Abstract:
Analysis of the long-term (2005-2020) winds acquired from Skiymet meteor radar located at Rothera (67.5°S, 68.1°W), Antarctica reveals large interannual variability in monthly mean zonal winds in the upper mesosphere lower thermosphere (UMLT) region (82-98 km) during austral summer months (November-December). Large westward UMLT winds in summer are observed during the years 2006–2011, 2015, 2018, and 2020, when there is polar stratospheric ozone loss. Similarly, winds in the stratosphere obtained from ERA-5 reanalysis datasets exhibit large interannual variability in the prevailing eastward winds during November. The reduced stratospheric meridional heat flux in those years, due primarily to the planetary wave (PW) of zonal wavenumber 1 (k=1), decreases the polar stratospheric temperature. This provides a favorable condition for the increased polar stratospheric clouds (PSCs) formation that results in ozone loss. The ozone loss leads to a large horizontal temperature gradient, which may generate strong stratospheric eastward wind with height due to thermal wind balance. These winds may filter the upward propagating waves having westward phase speed and lead to the deposition of westward momentum into the background flow. Further, the ozone loss is found to control the migrating semi-diurnal (SW2) tidal variabilities at the UMLT heights, with low activity during the years of more ozone loss. Results in this study thus provide observational evidence for the long-term impact of stratospheric meridional heat flux changes on the catalytic destruction of ozone over the Antarctic peninsula, which may govern the winds and tidal variabilities in the UMLT region.
