The Hunga Tonga–Hunga Ha‘apai volcanic eruption was one of the most vigorous volcanic explosions in the last centuries. The eruption launched many atmospheric waves traveling around the Earth. In this study, we identify these volcanic waves at the edge of space in the mesosphere/lower-thermosphere, leveraging wind observations conducted with multi-static meteor radars in northern Europe and with the Chilean Observation Network De Meteor Radars (CONDOR).

The layer of sodium atoms is generally located above 80 km. This study reports the significant enhancements of the sodium layer below 75 km where sodium atoms are short-lived. The neutral chemical reactions were suggested as making a critical contribution. The reported results provide clear observational evidence for the role of planetary waves in the variation of metal layers, and have implications for the response of the metal layers to perturbations in the lower atmosphere.

Precise and accurate measurements of vertical winds at the mesosphere and lower thermosphere are rare. Although meteor radars have been used for decades to observe horizontal winds, their ability to derive reliable vertical wind measurements was always questioned. In this article, we provide mathematical concepts to retrieve mathematically and physically consistent solutions, which are compared to the state-of-the-art non-hydrostatic model UA-ICON.

Wind observations at the edge to space, 70–110 km altitude, are challenging. Meteor radars have become a widely used instrument to obtain mean wind profiles above an instrument for these heights. We describe an advanced mathematical concept and present a tomographic analysis using several meteor radars located in Finland, Sweden and Norway, as well as Chile, to derive the three-dimensional flow field. We show an example of a gravity wave decelerating the mean flow.

In the past, additional sodium peaks occurring above the main sodium layer of the upper mesosphere were discussed. Here, formation of an additional sodium peak below the main sodium layer peak is discussed in detail. The event coincided with passage of multiple mesospheric bores, which are step-like disturbances occurring in the upper mesosphere. Hence, this work highlights the importance of such mesospheric bores in causing significant changes to the minor species concentration in a short time.