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| Titel |
The interaction between Gravity Waves and Solar Tides: results from 4D Ray Tracing coupled to a Linear Tidal Model |
| VerfasserIn |
Bruno Ribstein, Ulrich Achatz, Fabian Senf |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250105435
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| Publikation (Nr.) |
 EGU/EGU2015-4959.pdf |
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| Zusammenfassung |
| Internal gravity waves contribute to an important part in the variability of the Stratosphere -
Mesosphere - lower - Thermosphere. Numerous General Circulation Model do not
present (for exemple) a Quasi-biennale Oscillation. Moreover, Internal gravity waves
parameterizations often neglect time and horizontal dependence of the background flow
(“column approximation”).
Interactions between internal gravity waves and large scale flow, specially Solar
tide waves, are studied here. Thermally driven global scaled waves, Solar tides
describe the large-scale modulation (at sub-daily period) of all middle atmosphere
fields.
Gravity waves propagate in a time and spatially varying background flow, composed by a
climatological mean, stationary planetary waves and diurnal Solar tides. Global
three-dimensional propagation of internal gravity waves is performed by a new W. K. B.
gravity wave model (ray tracer scheme), where waves propagate in position-wavenumber
phase-space in order to prevent the crossing of rays. Propagation of Solar tides is modeled by
linearising a General Circulation Model over a climatological mean and a stationnary
planetary waves reference.
Gravity wave deposition of momentum and buoyancy are calculated. Characterizing
the daily evolution, Rayleigh-friction and temperature-relaxation coefficients are
calculated. They approximately describe the internal gravity wave forcing on the diurnal
Solar tides propagation and are so used for it. The extracted diurnal Solar tides
are then used for a new computation of the gravity wave fluxes. This is iterated
a few times to obtain a converged result on gravity wave deposition and on tidal
field.
Internal gravity waves are shown to influence both Solar tides amplitude and phase.
Seasonal cycle of migrating and non-migrating tidal components is studied, as it is the
seasonal cycle of gravity wave deposition. Gravity wave deposition and tidal fields are also
obtained under the “column approximation”. They show a clear rise in gravity wave
deposition.
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Key words: Middle-Atmosphere dynamics, Solar Tides, Internal Gravity Waves
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