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Ann. Geophys., 15, 1187-1197, 1997
www.ann-geophys.net/15/1187/1997/
© European Geosciences Union 1997
SMLTM simulations of the diurnal tide: comparison with UARS observations
R. A. Akmaev1, V. A. Yudin2, and D. A. Ortland3
1Department of Aerospace Engineering Sciences, Campus Box 429, University of Colorado, Boulder, CO 80309-0429, USA
2Institute for Terrestrial and Planetary Atmospheres, State University of New York at Stony Brook, Stony Brook, NY 11794-5000, USA
3Space Physics Research Laboratory, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA
Abstract. Wind and temperature observations in the
mesosphere and lower thermosphere (MLT) from the Upper Atmosphere Research
Satellite (UARS) reveal strong seasonal variations of tides, a dominant
component of the MLT dynamics. Simulations with the Spectral mesosphere/lower
thermosphere model (SMLTM) for equinox and solstice conditions are presented and
compared with the observations. The diurnal tide is generated by forcing
specified at the model lower boundary and by in situ absorption of solar
radiation. The model incorporates realistic parameterizations of physical
processes including various dissipation processes important for propagation of
tidal waves in the MLT. A discrete multi-component gravity-wave parameterization
has been modified to account for seasonal variations of the background
temperature. Eddy diffusion is calculated depending on the gravity-wave energy
deposition rate and stability of the background flow. It is shown that seasonal
variations of the diurnal-tide amplitudes are consistent with observed
variations of gravity-wave sources in the lower atmosphere.
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