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| Titel |
Kelvin-Helmholtz billows and their effects on mean state during gravity wave propagation |
| VerfasserIn |
X. Liu, J. Xu, H. Gao, G. Chen |
| 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 ; 27, no. 7 ; Nr. 27, no. 7 (2009-07-14), S.2789-2798 |
| Datensatznummer |
250016589
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| Publikation (Nr.) |
 copernicus.org/angeo-27-2789-2009.pdf |
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| Zusammenfassung |
| The Kelvin-Helmholtz (KH) billows which appear in the process of gravity
wave (GW) propagation are simulated directly by using a compressible
nonlinear two-dimensional gravity wave model. The differences between our
model and others include: the background field has no special initial
configuration and there is no initial triggering mechanism needed in the
mesosphere and lower thermosphere (MLT) region to excite the KH billows.
However, the initial triggering mechanism is performed in the lower
atmosphere through GW, which then propagate into the MLT region and form
billows. The braid structures and overturning of KH billows, caused by
nonlinear interactions between GWs and mean flow, can be resolved precisely
by the model. These results support the findings in airglow studies that GWs
propagating from below into the MLT region are important sources of KH
billows. The onset of small scale waves and the wave energy transfer induce
the shallower vertical wave number power spectral densities (PSD). However,
most of the slopes are steeper than the expected kz−3 power law,
which indicates that GWs with 10 km vertical wavelength are still a dominant
mode. The results also show that the evolution of mean wind vary
substantially between the different processes of GWs propagation. Before the
KH billows evolve, the mean wind is accelerated greatly by GWs. By contrast,
as the KH billows evolve and mix with mean flow, the mean wind and its peak
value decrease. |
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