Gravity waves are periodic oscillations of temperature, air density, pressure, und wind. They are observed in the whole middle atmosphere. The periods of these oscillations are between a few minutes and several hours, horizontal wave lengths range from 10 km to some thousands of kilometers, and vertical wavelenghts from a few kilometers to 30 km. Gravity waves are generated, among others, by orography, at strong convection cells (e.g., like thunder storms), or at the jet stream in the tropopause region.
Gravity waves are an important driver on the atmospheric circulation. They transport energy and momentum from the place of their generation upward to the middle atmosphere where they break. There, energy and momentum are transfered to the background atmosphere. In this manner gravity waves drive the residual circulation. This circulation from the summer pole to the winter pole is the reason for the cold summer mesopause.
Gravity waves in wind and temperatur data and in noctilucent clouds (NLC) are studied by lidar measurements. Wind measurements above Andenes allow for the first time to derive the potential and the kinetic gravity-wave energy simultaneously. Since temperatures of the mesosphere above Kühlungsborn and Andenes are measured since several years, seasonal variations of the wave activity can be studied.
While the temporal resolution of these data is mostly about one hour, the strong backscatter signal from NLC allows the observation of short-periodic gravity waves.
The two-dimensional structure of gravity waves in airglow (OH layer at about 87 km) is observed by special cameras. The deduced temperatures are compared to vertical temperature profiles derived by lidar.
- Baumgarten, K., M. Gerding, G. Baumgarten, and F.-J. Lübken Temporal variability of tidal and gravity waves during a record long 10 day continuous lidar sounding, Atmos. Chem. Phys., 18, 371–384, doi:10.5194/acp-18-371-2018, 2018
- Baumgarten, K., M. Gerding, and F.-J. Lübken, Seasonal variation of gravity wave parameters using different filter methods with daylight lidar measurements at mid-latitudes, J. Geophys. Res., 122, doi:10.1002/2016JD025916, 2017
- G. Baumgarten und D. C. Fritts, Quantifying Kelvin-Helmholtz instability dynamics observed in Noctilucent Clouds: 1. methods and observations, J. Geophys. Res., 9324–9337, doi:10.1002/2014JD021832, 2014.
- N. Kaifler, G. Baumgarten, J. Fiedler und F.-J. Lübken, Quantification of waves in lidar observations of noctilucent clouds at scales from seconds to minutes, Atmos. Chem. Phys., 13, 11757-11768, doi:10.5194/acp-13-11757-2013, 2013.
- N. Kaifler, G. Baumgarten, A. R. Klekociuk, S. P. Alexander, J. Fiedler und F.-J. Lübken, Small scale structures of NLC observed by lidar at 69°N/69°S and their possible relation to gravity waves, J. Atmos. Solar-Terr. Phys., 104, 244-252, doi:10.1016/j.jastp.2013.01.004, 2013.
- S. Suzuki, F.-J. Lübken, G. Baumgarten, N. Kaifler, R. Eixmann, B. P. Williams und T. Nakamura, Vertical propagation of mesoscale gravity wave from the lower to the upper atmosphere, J. Atmos. Solar-Terr. Phys., 97, 29-36, doi:10.1016/j.jastp.2013.01.012, 2013.
- H. Wilms, M. Rapp, P. Hoffmann, J. Fiedler und G. Baumgarten, Gravity wave influence on NLC: Experimental results from ALOMAR, 69°N, Atmos. Chem. Phys., 13, 11951-11963, doi:10.5194/acp-13-11951-2013, 2013.
- J. Hildebrand, G. Baumgarten, J. Fiedler, U.-P. Hoppe, B. Kaifler, F.-J. Lübken und B. P. Williams, Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere, Atmos. Meas. Tech., 5, 2433-2445, doi:10.5194/amt-5-2433-2012, 2012
Dr. Jens Hildebrand
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