We find a sudden stratospheric warming (SSW) effect in the F2 critical frequency (foF2) series for Okinawa. Across 29 SSW events, the amplitude of the semidiurnal cycle of foF2 peaks at the SSW onset in the SSW years. In these years, we find, for the first time, a lunar terdiurnal component with a relative amplitude of about 5 %, and lunar diurnal and semidiurnal components have relative amplitudes of about 10 %. The periods of lunar ionospheric tidal variations align with those of ocean tides.

Investigation of winds is important to understand atmospheric dynamics. In the summer mesosphere and lower thermosphere, there are three main wind flows: the mesospheric westward, the mesopause southward (equatorward), and the lower-thermospheric eastward wind. Combining almost 2 decades of measurements from different radars, we study the trend, their interannual oscillations, and the effects of the geomagnetic activity over these wind maxima.

The geomagnetic and solar effect on Es is studied. The negative correlation between Es and geomagnetic activity at mid-latitude is related to the decreased meteor rate during storm period. The increased Es occurrence in high latitude relates to the changing electric field. The positive correlation between Es and solar activity at high latitude is due to the enhanced IMF in solar maximum. The negative correlation in mid and low latitudes relates to the decreased meteor rate during solar activity.

We use long term radar data and the WACCM-X model to study the impact of dynamical phenomena, including the 11-year solar cycle, ENSO, QBO and SAM, on Antarctic mesospheric winds. We find that in summer, the zonal wind (both observationally and in the model) is strongly correlated with the solar cycle. We also see important differences in the results from the other processes. In addition we find important and large biases in the winter model zonal winds relative to the observations.

In order to have confidence in atmospheric predictions, it is important to know how well different numerical model simulations of the Earth’s atmosphere agree with one another. This work compares four different data assimilation models that extend to or beyond the mesosphere. Results shown here demonstrate that while the models are in close agreement below ~50 km, large differences arise at higher altitudes in the mesosphere and lower thermosphere that will need to be reconciled in the future.

Little is known about the climate change of wind systems in the mesosphere and lower thermosphere at the edge of space at altitudes from 70–110 km. Meteor radars represent a well-accepted remote sensing technique to measure winds at these altitudes. Here we present a state-of-the-art climatological interhemispheric comparison using continuous and long-lasting observations from worldwide distributed meteor radars from the Arctic to the Antarctic and sophisticated general circulation models.

With global warming, water vapour increases in the atmosphere. Water vapour is an important gas because it is a natural greenhouse gas and affects the formation of clouds, rain and snow. How much water vapour increases can vary in different regions of the world. To verify if it increases as expected on a regional scale, we analysed water vapour measurements in Switzerland. We found that water vapour generally increases as expected from temperature changes, except in winter.

We measured middle-atmospheric ozone, water vapour and zonal and meridional wind with two ground-based microwave radiometers which are located at Ny-Alesund, Svalbard, in the Arctic. In this article we present measurements of the small-scale horizontal ozone gradients during winter 2018/2019. We found a distinct seasonal variation of the ozone gradients which is linked to the planetary wave activity. We further present the signatures of the SSW in the ozone, water vapour and wind measurements.