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| Titel |
The interaction between atmospheric gravity waves and large-scale flows: an efficient description beyond the non-acceleration paradigm |
| VerfasserIn |
Gergely Bölöni, Bruno Ribstein, Jewgenija Muraschko, Christine Sgoff, Junhong Wei, Ulrich Achatz |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138663
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| Publikation (Nr.) |
 EGU/EGU2017-1757.pdf |
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| Zusammenfassung |
| With the aim of contributing to the improvement of subgrid-scale gravity wave (GW)
parameterizations in numerical-weather-prediction and climate models, the comparative
relevance in GW drag of direct GW-mean-flow interactions and turbulent wave breakdown
are investigated. Of equal interest is how well Wentzel-Kramer-Brillouin (WKB) theory can
capture direct wave-mean-flow interactions, that are excluded by applying the steady-state
approximation. WKB is implemented in a very efficient Lagrangian ray-tracing approach that
considers wave action density in phase-space, thereby avoiding numerical instabilities due to
caustics (Muraschko et al., 2015, Quart. J. Roy. Meteor. Soc., 141, 676–697). It is
supplemented by a simple wave-breaking scheme based on a static-instability saturation
criterion. Idealized test cases of horizontally homogeneous GW packets are considered where
wave-resolving Large-Eddy Simulations (LES) provide the reference. In all of theses cases
the WKB simulations including direct GW-mean-flow interactions reproduce the LES data, to
a good accuracy, already without wave-breaking scheme. The latter provides a
next-order correction that is useful for fully capturing the total-energy balance between
wave and mean flow. Moreover, a steady-state WKB implementation, as used in
present GW parameterizations, and where turbulence provides, by the non-interaction
paradigm, the only possibility to affect the mean flow, is much less able to yield
reliable results. The GW energy is damped too strongly and induces an oversimplified
mean flow. This argues for WKB approaches to GW parameterization that take
wave transience into account (Bölöni et al., 2016 J. Atmos. Sci., 73, 4833–4852). |
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