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| Titel |
Spontaneous emission of gravity waves in idealized flows |
| VerfasserIn |
Riwal Plougonven, Chris Snyder |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040996
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| Zusammenfassung |
| The coupling mechanisms between balanced motions and gravity waves have been an
outstanding issue in research on the limitaions of balanced motions and on the
sources of gravity waves for two decades. Some recent advances have come from the
study of certain idealized flows simple enough for an explanation of the generation
mechanism to be proposed. More precisely, simulations of idealized baroclinic life cycles
have shown that waves generated by upper-level jets appeared in regions of strong
strain and vertical shear. Simulations of dipoles have confirmed the importance
of such regions (jet exit regions), but are simpler because the background flow is
nearly stationary in the appropriate frame of reference (frame moving with the
dipole).
The mechanism for the emission of inertia-gravity waves in the jet exit region of
a dipole is explained using primitive equation simulations of a dipole and linear
simulations of the evolution of perturbations to a balanced dipole. The background
flow on which the linearization is made is crucial to determine the structure and
characteristics of the emitted waves. The calculation of the forcing, coming from residual
tendencies which appear when balanced fields are injected into the primitive equations,
is crucial to determine the amplitude of the waves. Using the linear model and
information coming only from the balanced dipole, we obtain an estimate of the
emitted waves that compares well with those obtained in the full primitive equation
simulations.
Based on the example of the dipole, diagnostics that give indications regarding the
location and amplitude of spontaneously emitted waves are derived and tested in simulations
of idealized baroclinic life cycles. Their use for applications and parameterizations is
discussed. |
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