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| Titel |
Macroscopic impacts of cloud and precipitation processes on maritime shallow convection as simulated by a large eddy simulation model with bin microphysics |
| VerfasserIn |
W. W. Grabowski, L.-P. Wang, T. V. Prabha |
| 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 ; 15, no. 2 ; Nr. 15, no. 2 (2015-01-27), S.913-926 |
| Datensatznummer |
250119347
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| Publikation (Nr.) |
 copernicus.org/acp-15-913-2015.pdf |
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| Zusammenfassung |
| This paper discusses impacts of cloud and precipitation processes
on macrophysical properties of shallow convective clouds as simulated
by a large eddy model applying warm-rain bin microphysics. Simulations
with and without collision–coalescence are considered with cloud condensation
nuclei (CCN) concentrations of 30, 60, 120, and 240 mg−1. Simulations
with collision–coalescence include either the standard gravitational
collision kernel or a novel kernel that includes enhancements due
to the small-scale cloud turbulence. Simulations with droplet
collisions were discussed in Wyszogrodzki et al. (2013) focusing
on the impact of the turbulent collision kernel. The current paper
expands that analysis and puts model results in the context of
previous studies. Despite a significant increase of the drizzle/rain
with the decrease of CCN concentration, enhanced by the effects of
the small-scale turbulence, impacts on the macroscopic cloud field
characteristics are relatively minor. Model results show a systematic
shift in the cloud-top height distributions, with an increasing
contribution of deeper clouds for stronger precipitating cases. We
show that this is consistent with the explanation suggested in
Wyszogrodzki et al. (2013); namely, the increase of drizzle/rain
leads to a more efficient condensate offloading in the upper
parts of the cloud field. A second effect involves suppression of
the cloud droplet evaporation near cloud edges in low-CCN simulations,
as documented in previous studies (e.g., Xue and Feingold, 2006).
We pose the question whether the effects of cloud turbulence on
drizzle/rain formation in shallow cumuli
can be corroborated by remote sensing
observations, for instance, from space. Although a clear signal is
extracted from model results, we argue that the answer is negative
due to uncertainties caused by the temporal variability of the
shallow convective cloud field, sampling and spatial resolution of
the satellite data, and overall accuracy of remote sensing retrievals. |
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