Middle Atmosphere

Above the troposphere that is home to our daily weather, we find the stratosphere, the mesosphere and the thermosphere. These layers, that are defined based on their thermal structure, are coupled by atmospheric waves. Waves transport energy and momentum over large distances, redistributing these quantities in our atmosphere. This can lead to substantial deviations from radiative equilibrium, for example at the very cold polar summer mesopause, and induces a global circulation. Atmospheric tides generate winds of up to 100 metres per second in the mesosphere. In the stratosphere, winds are decelerated by the breaking of gravity waves generated e.g. by wind overflowing mountains in wintertime. The thermosphere connects our atmosphere to space, and inflowing solar wind is known to induce storms. The propagation of atmospheric waves is influenced by a variety of processes, such as their interaction with winds or other waves. Secondary and higher-order waves can be generated that again propagate in all directions. Breaking waves create a variety of instabilities and turbulence through a cascade down to smaller scales. Observing the atmosphere and identifying and studying the dynamic processes at the various scales is essential to gaining an understanding of our atmosphere as a whole.

Questions to be addressed

  • Investigation of the entire life cycle of atmospheric gravity waves, including generation, horizontal and vertical propagation, and dissipation with momentum transfer from the waves to the mean flow and resulting acceleration or decleration of the flow
  • Investigation of the role of jet streams acting as wave guides for gravity waves
  • Study of processes which lead to breaking of gravity waves, the generation of higher-order waves and turbulence
  • Investigation of the interdependency between gravity waves among themselves, as well as between gravity waves and planetary waves and tides
  • The influence of the dynamics of the neutral atmosphere on space weather

For this research we combine in-situ and remote sensing measurements of atmospheric parameters obtained from ground as well as from aircrafts, balloons, sounding rockets and satellites with idealized numerical simulations, numerical weather prediction and climate models. We develop powerful and novel lidar instruments, which we deploy in extended field measurement campaigns to specifically target selected dynamics processes.

The research aircraft HALO during testing of the novel ALIMA lidar before the start of the  SouthTRAC campaign in southern Argentina. With ALIMA, atmospheric temperature and gravity waves are measured from flight altitude to 100 km altitude at one minute resolution. (Photo: ©bigair)

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