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| Titel |
Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere |
| VerfasserIn |
X. Liu, J. Xu, J. Yue, S. L. Vadas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 31, no. 1 ; Nr. 31, no. 1 (2013-01-03), S.1-14 |
| Datensatznummer |
250017313
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1-2013.pdf |
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| Zusammenfassung |
| We study the momentum deposition in the thermosphere from the dissipation of
small amplitude gravity waves (GWs) within a wave packet using a fully
nonlinear two-dimensional compressible numerical model. The model solves the
nonlinear propagation and dissipation of a GW packet from the stratosphere
into the thermosphere with realistic molecular viscosity and thermal
diffusivity for various Prandtl numbers. The numerical simulations are
performed for GW packets with initial vertical wavelengths (λz)
ranging from 5 to 50 km. We show that λz decreases in
time as a GW packet dissipates in the thermosphere, in agreement with the
ray trace results of Vadas and Fritts (2005) (VF05). We also find good
agreement for the peak height of the momentum flux (zdiss) between our
simulations and VF05 for GWs with initial λz ≤ 2π H in
an isothermal, windless background, where H is the density scale height. We
also confirm that zdiss increases with increasing Prandtl number. We
include eddy diffusion in the model, and find that the momentum deposition
occurs at lower altitudes and has two separate peaks for GW packets with
small initial λz. We also simulate GW packets in a
non-isothermal atmosphere. The net λz profile is a competition
between its decrease from viscosity and its increase from the increasing
background temperature. We find that the wave packet disperses more in the
non-isothermal atmosphere, and causes changes to the momentum flux and
λz spectra at both early and late times for GW packets with
initial λz ≥ 10 km. These effects are caused by the
increase in T in the thermosphere, and the decrease in T near the mesopause. |
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