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| Titel |
A review of the theoretical basis for bulk mass flux convective parameterization |
| VerfasserIn |
R. S. Plant |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 8 ; Nr. 10, no. 8 (2010-04-16), S.3529-3544 |
| Datensatznummer |
250008356
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| Publikation (Nr.) |
 copernicus.org/acp-10-3529-2010.pdf |
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| Zusammenfassung |
| Most parameterizations for precipitating convection in use today are bulk schemes, in which
an ensemble of cumulus elements with different properties is modelled as a single,
representative entraining-detraining plume. We review the underpinning mathematical model
for such parameterizations, in particular by comparing it with spectral models in which
elements are not combined into the representative plume. The chief merit of a bulk model is
that the representative plume can be described by an equation set with the same structure as
that which describes each element in a spectral model. The equivalence relies on an ansatz
for detrained condensate introduced by Yanai et al. (1973) and on a simplified microphysics. There
are also conceptual differences in the closure of bulk and spectral parameterizations. In
particular, we show that the convective quasi-equilibrium closure of Arakawa and Schubert (1974) for
spectral parameterizations cannot be carried over to a bulk parameterization in
a straightforward way. Quasi-equilibrium of the cloud work function assumes a timescale
separation between a slow forcing process and a rapid convective response. But, for the
natural bulk analogue to the cloud-work function, the relevant forcing is
characterised by a different timescale, and so its quasi-equilibrium entails a different
physical constraint. Closures of bulk parameterizations that use a parcel
value of CAPE do not suffer from this timescale issue. However, the Yanai et al. (1973) ansatz
must be invoked as a necessary ingredient of those closures. |
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