Enhancement of Quasi-6-Day Wave during the 2019 Southern Hemisphere (SH) sudden stratospheric warming and its influence on diurnal tides and gravity waves observed by two meteor radars at SH midlatitudes

A westward-propagating wavenumber 1 Quasi-6-Day Wave (Q6DW) activity occurring prior to and during the 2019 southern hemispheric minor sudden stratospheric warming (SSW) is determined by wind measurements in the 80-100 km region from Buckland Park meteor radar (34.6S,138.5E) in Australia and a newly established multi-static meteor radar network CONDOR (31.2S,70.0W) in Chile. Along with this Q6DW enhancement, the CONDOR wind measurements also showed a strong 6-day periodicity in both diurnal tide amplitude and gravity wave (GW) variance in meridional wind, computed by 3DVAR algorithm. This algorithm creates a tomographic reconstruction of the 3D wind field based on optimal estimation technique and Bayesian statistics, and is particularly suitable for investigating GW dynamics on regional scales. Additionally, the CONDOR wind and temperature measurement were combined to derive the EliassonPalm (EP) flux of Q6DW during this period. The EP flux showed that there was strong equatorward eddy heat flux and potential planetary wave breaking during this period. The radar-measured Q6DW EP flux was also compared with WACCAM simulations which provide a global context of the Q6DW enhancement. The observational results demonstrated that the SH mid-latitude MLT region had a significant response to this Q6DW activity which was believed to be associated with the SH SSW. This work also demonstrated the capability of the CONDOR meteor radar network in resolving oscillations over a broad range of periods, and for calculating EP flux of planetary waves.