Observations of Eastward Propagating Quasi 6‐Day Waves From the Troposphere to the Lower Thermosphere During SSWs in Early 2016

There are few reports on quasi 6-day wave (Q6DW) during stratospheric sudden warming (SSW) events, especially the eastward propagating one. By using observations from three meteor radars and three radiosondes combined with reanalysis data from January to March 2016, we study the eastward propagating Q6DWs during the SSWs from the troposphere to the mesosphere and lower thermosphere (MLT). There are SSW and stratospheric final warming (SFW) events around February and March in the northern hemisphere, respectively. The polar mean temperature rises by about 45 and 36 K at 10-hPa level and the mean zonal wind decreases by about 38 and 49 ms(-1) during the SSW and SFW, respectively. Large-scale zonal wind reversal happens during the SSWs. Radar observations and reanalysis data show that two Q6DWs corresponding to the SSWs are robust from the troposphere to the MLT. They are eastward traveling waves with zonal wavenumbers 1-2. The Q6DWs propagate downward in the stratosphere and upward in the MLT, implying that the source of the Q6DWs is in the mesosphere. The meridional gradient of quasi-geostrophic potential vorticity and Eliassen-Palm flux divergence show that the instabilities possibly occur in the mesosphere, which likely in situ excite and strengthen the Q6DWs. The instabilities are also found in the stratosphere and may amplify the Q6DWs in the stratosphere at the three stations especially during the SSW.