Mountain waves penetrating into the mesosphere observed by airborne lidar

We present observations by airborne lidar which were obtained over the southern Andes during the SOUTHTRAC campaign in September 2019. Operated onboard the German research aircraft HALO, the Airborne LIdar for Middle Atmosphere research (ALIMA) acquired high resolution temperature profiles in the altitude range 20-80 km. The data show signatures of mountain waves located at the mountain ridges, but often these signatures also extend several hundred kilometer downstream. While during the first days of the campaign mountain waves were able to penetrate into the mesosphere, observations obtained in the following weeks indicate a downward shift of the breaking zone from the mesosphere to the stratosphere which is consistent with the early breakdown of the polar vortex. Our data also indicate evidence for generation of secondary gravity waves within the breaking zone of the mountain waves.