The Open UniversitySkip to content

Caustic activation of rain showers

Wilkinson, Michael; Mehlig, Bernhard and Bezuglyy, Vlad (2006). Caustic activation of rain showers. Physical Review Letters, 97 048501.

DOI (Digital Object Identifier) Link:
Google Scholar: Look up in Google Scholar


We show quantitatively how the collision rate of droplets of visible moisture in turbulent air increases very abruptly as the intensity of the turbulence passes a threshold, due to the formation of fold caustics in their velocity field. The formation of caustics is an activated process, in which a measure of the intensity of the turbulence, termed the Stokes number St, is analogous to temperature in a chemical reaction: the rate of collision contains a factor exp(-C/St). Our results are relevant to the long-standing problem of explaining the rapid onset of rainfall from convecting clouds. Our theory does not involve spatial clustering of particles.

Item Type: Journal Article
ISSN: 0031-9007
Keywords: caustics; rain; turbulence; aerosol; kinetics
Academic Unit/Department: Mathematics, Computing and Technology > Mathematics and Statistics
Item ID: 9340
Depositing User: Michael Wilkinson
Date Deposited: 27 Sep 2007
Last Modified: 02 Dec 2010 20:04
Share this page:


Scopus Citations

Actions (login may be required)

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340