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| Titel |
Turbulent collision-coalescence in maritime shallow convection |
| VerfasserIn |
A. A. Wyszogrodzki, W. W. Grabowski, L.-P. Wang, O. Ayala |
| 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 ; 13, no. 16 ; Nr. 13, no. 16 (2013-08-27), S.8471-8487 |
| Datensatznummer |
250085653
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| Publikation (Nr.) |
 copernicus.org/acp-13-8471-2013.pdf |
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| Zusammenfassung |
| This paper discusses cloud simulations aiming at quantitative
assessment of the effects of cloud turbulence on rain development
in shallow ice-free convective clouds. Cloud fields from large-eddy
simulations (LES) applying bin microphysics with the collection
kernel enhanced by cloud turbulence are compared to those with the
standard gravitational collection kernel. Simulations for a range
of cloud condensation nuclei (CCN) concentrations are contrasted.
Details on how the parameterized turbulent collection kernel is used
in LES simulations
are presented. Because of the disparity in spatial scales between
the bottom-up numerical studies guiding the turbulent kernel
development and the top-down LES simulations of cloud dynamics, we
address the consequence of the turbulence intermittency in the
unresolved range of scales on the mean collection kernel applied
in LES. We show that intermittency effects are unlikely to play an
important role in the current simulations. Highly-idealized
single-cloud simulations are used to illustrate two mechanisms that
operate in cloud field simulations. First, the microphysical
enhancement leads to earlier formation of drizzle through faster
autoconversion of cloud water into drizzle, as suggested by previous
studies. Second, more efficient removal of condensed water from
cloudy volumes when a turbulent collection kernel is used leads to
an increased cloud buoyancy and enables clouds to reach higher
levels. This is the dynamical enhancement. Both mechanisms operate
in the cloud field simulations. The microphysical enhancement leads
to the increased drizzle and rain inside clouds in simulations with
high CCN. In low-CCN simulations with significant surface rainfall,
dynamical enhancement leads to a larger contribution of deeper
clouds to the entire cloud population, and results in a dramatically
increased mean surface rain accumulation. These results call for
future modeling and observational studies to corroborate the findings. |
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