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| Titel |
Frequency variations of gravity waves interacting with a time-varying tide |
| VerfasserIn |
C. M. Huang, S. D. Zhang, F. Yi, K. M. Huang, Y. H. Zhang, Q. Gan, Y. Gong |
| 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. 10 ; Nr. 31, no. 10 (2013-10-18), S.1731-1743 |
| Datensatznummer |
250086125
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1731-2013.pdf |
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| Zusammenfassung |
| Using a nonlinear, 2-D time-dependent numerical model, we simulate the
propagation of gravity waves (GWs) in a time-varying tide. Our simulations
show that when a GW packet propagates in a time-varying tidal-wind
environment, not only its intrinsic frequency but also its ground-based
frequency would change significantly. The tidal horizontal-wind acceleration
dominates the GW frequency variation. Positive (negative) accelerations
induce frequency increases (decreases) with time. More interestingly,
tidal-wind acceleration near the critical layers always causes the GW
frequency to increase, which may partially explain the observations that
high-frequency GW components are more dominant in the middle and upper
atmosphere than in the lower atmosphere. The combination of the increased
ground-based frequency of propagating GWs in a time-varying tidal-wind field
and the transient nature of the critical layer induced by a time-varying
tidal zonal wind creates favorable conditions for GWs to penetrate their
originally expected critical layers. Consequently, GWs have an impact on the
background atmosphere at much higher altitudes than expected, which indicates
that the dynamical effects of tidal–GW interactions are more complicated
than usually taken into account by GW parameterizations in global models. |
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