Numerical modelling is used to simulate atmospheric circulation and calculate residual mean meridional circulation (RMC) during sudden stratospheric warming (SSW) events. Calculating the RMC is used to take into account wave effects on the transport of atmospheric quantities and gas species in the meridional plane. The results show that RMC undergoes significant changes at different stages of SSW and contributes to SSW development.

One of the fundamental tasks of atmospheric physics is the study of the processes of vertical interaction of atmospheric layers. We carried out observations with a Fabry–Perot interferometer at an altitude of 90–100 km. We have shown that sudden stratospheric warming and active planetary waves have an impact on the dynamics of the upper atmosphere. That is, the green line airglow decreases and the temperature rises. Major warming causes the reversal of the zonal wind in the upper atmosphere.

Temperatures obtained from FORMOSAT-3 and COSMIC observations in the stratosphere are analysed for tidal variations. It is seen that non-migrating tides are not very significant in the high-latitude winter stratosphere. It is shown that the observed amplitudes of these tides in earlier studies are most probably a result of aliasing and are not geophysical in nature. Thus, the process of non-linear interactions through which it was believed that they are produced seems to be unimportant.

The aim of this study is to bring local variabilities into a global context. To qualitatively study the impact of global waves on local measurements in winter, we combine local lidar measurements with global MERRA-2 reanalysis data. Our results show that about 98 % of the local day-to-day variability can be explained by the variability of waves with zonal wave numbers 1, 2 and 3. Thus locally measured effects which are not based on global wave variability can be investigated much better.

Interannual variabilities of the zonal mean wind and temperature related to the Rossby wave forcing in the winter stratosphere of the Southern Hemisphere are studied using 38-year reanalysis data. Correlation of the mean fields to the wave forcing is extended to the subtropics of the Northern Hemisphere. This interhemispheric link is caused by the wave forcing which reduces the meridional gradient of the angular momentum and drives the meridional circulation over the Equator in the stratosphere.