Understanding the Excitation of Quasi‐6‐Day Waves in Both Hemispheres During the September 2019 Antarctic SSW

Responses of quasi‐6‐day waves (Q6DWs) to the extreme 2019 Antarctic stratospheric sudden warming (SSW) have been widely reported in the ionosphere, while the excitation mechanism of the global Q6DWs is still unclear in the mesosphere and lower thermosphere (MLT) region. According to the Aura satellite measurements, the amplitudes of the Q6DWs in the upper MLT region are found to be higher than their climatological activities from 2005 to 2020 at mid‐latitudes in both Northern and Southern Hemispheres. Combined with the Modern‐Era Retrospective Analysis for Research and Applications, version 2 data, the trigger mechanisms of the global enhanced Q6DWs are investigated by tracing their sources and propagations. Our analysis indicates that the equatorward propagation induced by the SSW is the main reason for the enhanced Q6DWs in the upper MLT at mid‐latitudes in the Southern Hemisphere, and the main source of the Q6DWs in the Northern Hemisphere is the seasonal variability. Besides, interhemispheric propagations also contribute to the amplification of Q6DWs during the 2019 Antarctic SSW. Key Points The sources and propagations of the global extremely excited quasi‐6‐day waves (Q6DWs) in September 2019 are revealed The Antarctic warming and climatology are respectively responsible for the enhanced Q6DWs in the Southern and Northern Hemispheres Interhemispheric propagations have additional contributions to the global enhanced Q6DWs