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| Titel |
Dependence of aerosol-precipitation interactions on humidity in a multiple-cloud system |
| VerfasserIn |
S. S. Lee |
| 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 ; 11, no. 5 ; Nr. 11, no. 5 (2011-03-11), S.2179-2196 |
| Datensatznummer |
250009454
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| Publikation (Nr.) |
 copernicus.org/acp-11-2179-2011.pdf |
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| Zusammenfassung |
This study examines the dependence of aerosol-precipitation interactions on
environmental humidity in a mesoscale cloud ensemble (MCE) which is composed
of convective and stratiform clouds. The author found that increases in
aerosol concentration enhance evaporative cooling, which raises not only the
intensity of vorticity and entrainment but also that of downdrafts and
low-level convergence. The increase in vorticity tends to suppress
precipitation. The increase in low-level convergence tends to enhance
precipitation by generating more secondary clouds in a muptiple-cloud system
simulated here.
At high humidity, the effect of the increased vorticity on cloud-liquid mass
and, thus, precipitation is outweighed by that of the increased low-level
convergence. This leads to the precipitation enhancement induced by the
increase in aerosol concentration. When humidity lowers to mid humidity, the
effect of aerosol on low-level convergence still dominates that on
entrainment, leading to the precipitation enhancement with the increased
aerosol concentration. With the lowest humidity in the current work, the
effect of aerosol on entrainment dominates that on low-level convergence,
leading to the precipitation suppression with the increased aerosol
concentration. Hence, there is not only a competition between the effect of
evaporation on vorticity and that on low-level convergence at a given
humidity level but also the variation of the competition with the varying
humidity. This competition and variation are absent in a single-cloud system
where the effect of low-level convergence on secondary clouds is absent.
This exemplifies a difference in the mechanism which controls
aerosol-precipitation interactions between a single-cloud system and a
multiple-cloud system. |
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