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| Titel |
The instability of internal gravity waves to localised disturbances |
| VerfasserIn |
J. Vanneste |
| 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 ; 13, no. 2 ; Nr. 13, no. 2, S.196-210 |
| Datensatznummer |
250011749
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| Publikation (Nr.) |
 copernicus.org/angeo-13-196-1995.pdf |
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| Zusammenfassung |
| The instability of an internal gravity wave
due to nonlinear wave-wave interaction is studied theoretically and numerically.
Three different aspects of this phenomenon are examined. 1. The influence of
dissipation on both the resonant and the nonresonant interactions is analysed
using a normal mode expansion of the basic equations. In particular, the
modifications induced in the interaction domain are calculated and as a result
some modes are shown to be destabilised by dissipation. 2. The evolution of an
initial unstable disturbance of finite vertical extent is described as the
growth of two secondary wave packets travelling at the same group velocity. A
quasi-linear correction to the basic primary wave is calculated, corresponding
to a localised amplitude decrease due to the disturbance growth. 3. Numerical
experiments are carried out to study the effect of a basic shear on wave
instability. It appears that the growing secondary waves can have a frequency
larger than that of the primary wave, provided that the shear is sufficient. The
instability of waves with large amplitude and long period, such as tides or
planetary waves, could therefore be invoked as a possible mechanism for the
generation of gravity waves with shorter period in the middle atmosphere. |
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