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- Title
Local Time Dependence of Polar Mesospheric Clouds: A model study.
- Authors
Schmidt, Francie; Baumgarten, Gerd; Berger, Uwe; Fiedler, Jens; Lübken, Franz-Josef
- Abstract
The Mesospheric Ice Microphysics And tranSport model (MIMAS) is used to study local time (LT) variations of polar mesospheric clouds (PMC) in the northern hemisphere during the period from 1979 to 2013. We investigate the tidal behavior of brightness, altitude and occurrence frequency and find a good agreement between model and lidar observations. Mean ice water content (IWC) values from MIMAS also match those from satellite observations. In the latitudinal band of 67.5° 70.5° N the IWC maximum throughout the day occurs at about 3 LT and the minimum around 18 LT with a ratio of maximum to minimum of 10. At the peak of the PMC layer the ice particle size varies by about 30% while the median number density varies by a factor of 2 throughout the day. Furthermore, the absolute tidal variation of IWC generally increases towards higher latitudes and the time of maximum IWC changes from about 4 to 0 LT for latitudes from 63° N to 81° N. In the period from 1979 to 2013 we find an increase of the tidal amplitudes. The linear trend terms of diurnal and semidiurnal variations are calculated to be 3.4 and 1.4 g/km²/dec. The persistent features of strong tidal modulations are caused by tidal structures in background parameters. The temperature varies by about 2 K and water vapor by about 3 ppmv at the altitude of ice particle sublimation near 81.5 km.
- Subjects
NOCTILUCENT clouds; MESOSPHERIC circulation; ATMOSPHERIC circulation; ATMOSPHERIC water vapor; SUBLIMATION (Chemistry)
- Publication
Atmospheric Chemistry & Physics Discussions, 2017, p1
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acp-2017-772