Gravity waves are primarily excited in the lower atmosphere, e.g. by flow over mountains. They propagate horizontally and vertically and transport energy and momentum over large distances. Gravity waves also interact with the background flow, and seasonal variations in the atmospheric wind field modulate gravity wave propagation. The deposition of energy and momentum in the atmosphere by breaking gravity waves modifies the thermal structure of the atmosphere as well as the circulation. In the summer mesopause region, breaking of gravity waves causes the background flow to accelerate. Air rises to about 100 km and is transported to the winter pole where it descends into the polar vortex. The upwelling of air leads to adiabatic cooling, making the summer mesopause the coldest region on Earth, reaching temperatures as low as -160 °C despite permanent solar irradiation. Thus, in climate models, the detailed representation of all gravity wave related processes such as generation, propagation and dissipation of waves is the indispensable precondition for an accurate description of the dynamic state of the atmosphere. The treatment of gravity waves in current models is, however, mostly limited to crude parametrizations. For this reason, the study of atmospheric gravity waves is still an active topic in atmospheric research.
Lidar is so far the only technology which allows the measurement of dynamic parameters such as temperature and wind in the middle atmosphere at altitudes from 10 to 100 km. Three lidar systems designed for gravity wave studies in the middle atmosphere are currently in development at the institute of atmospheric physics. ALIMA is an iron resonance and Rayleigh lidar which is slated for first operation onboard a research aircraft in 2017. TELMA and CORAL are two mobile ground-based lidar systems.