Preprints
https://doi.org/10.5194/acpd-11-10557-2011
https://doi.org/10.5194/acpd-11-10557-2011
05 Apr 2011
 | 05 Apr 2011
Status: this preprint was under review for the journal ACP but the revision was not accepted.

Initiation of coalescence in a cumulus cloud: a beneficial influence of entrainment and mixing

W. A. Cooper, S. G. Lasher-Trapp, and A. M. Blyth

Abstract. Although rain has been observed to form in warm cumulus clouds within about twenty minutes, calculations that represent condensation and coalescence accurately in such clouds have had difficulty producing rainfall in such a short time except via processes involving giant cloud condensation nuclei (with diameters larger than 2 μm). This model-based study explores a different possible mechanism for accelerating the production of warm rain, one that depends on the variability in droplet trajectories arriving at a given location and time in a cumulus cloud. In the presence of entrainment such droplets experience different growth histories, and the result is broadening of the droplet size distribution. That broadening favours coalescence, leading to embryos that grow to raindrops. These calculations do lead to production of rain that is within the lower range of observations for clouds of Florida, USA, the location on which the input conditions were based. The process emphasized in this study, the formation of drizzle via collisions among droplets in the main peak of the droplet size distribution, complements the growth of precipitation on giant nuclei, which is also an important source of the first rain in the case studied. The results indicate that the mechanism developed here should be considered an important influence on the formation of rain in warm clouds.

W. A. Cooper, S. G. Lasher-Trapp, and A. M. Blyth
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
W. A. Cooper, S. G. Lasher-Trapp, and A. M. Blyth
W. A. Cooper, S. G. Lasher-Trapp, and A. M. Blyth

Viewed

Total article views: 1,711 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
1,203 389 119 1,711 97 93
  • HTML: 1,203
  • PDF: 389
  • XML: 119
  • Total: 1,711
  • BibTeX: 97
  • EndNote: 93
Views and downloads (calculated since 01 Feb 2013)
Cumulative views and downloads (calculated since 01 Feb 2013)

Cited

Saved

Latest update: 28 Mar 2024
Download
Altmetrics