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| Titel |
Numerical evidence for cloud droplet nucleation at the cloud-environment interface |
| VerfasserIn |
J. Sun, H. Leighton, M. K. Yau, P. Ariya |
| 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 ; 12, no. 24 ; Nr. 12, no. 24 (2012-12-21), S.12155-12164 |
| Datensatznummer |
250011684
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| Publikation (Nr.) |
 copernicus.org/acp-12-12155-2012.pdf |
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| Zusammenfassung |
| Cumulus clouds have long been recognized as being the results of ascending
moist air from below the cloud base. Cloud droplet nucleation is understood
to take place near the cloud base and inside accelerating rising cloudy air.
Here we describe circumstances under which cloud droplet nucleation takes
place at the interface of ascending cloudy air and clear air. Evaporation is
normally expected to occur at this interface. However, continuity of moving
air requires cloud-free air above the boundary of rising cloudy air to move
upwards in response to the gradient force of perturbation pressure. We used a
one and half dimensional non-hydrostatic cloud model and the Weather Research
and Forecast model to investigate the impacts of this force on the evolution
of cloud spectra. Our study shows that expansion and cooling of ascending
moist air above the cloud top causes it to become supersaturated with
condensation rather than evaporation occurring at the interface. We also
confirm that Eulerian models can describe the cloud droplet activation and
prohibit spurious activation at this interface. The continuous feeding of
newly activated cloud droplets at the cloud summit may accelerate warm rain
formation. |
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