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Caustic activation of rain showers

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

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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: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Mathematics and Statistics
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 9340
Depositing User: Michael Wilkinson
Date Deposited: 27 Sep 2007
Last Modified: 04 Oct 2016 10:05
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