A coarsening model for self-organization of tropical convection
Article first published online: 20 AUG 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 16, pages 8761–8769, 27 August 2013
How to Cite
2013), A coarsening model for self-organization of tropical convection, J. Geophys. Res. Atmos., 118, 8761–8769, doi:10.1002/jgrd.50674., and (
- Issue published online: 18 SEP 2013
- Article first published online: 20 AUG 2013
- Accepted manuscript online: 26 JUL 2013 01:40AM EST
- Manuscript Accepted: 18 JUL 2013
- Manuscript Revised: 23 JUN 2013
- Manuscript Received: 12 FEB 2013
 If the influence of humidity on cumulus convection causes moist regions of the tropical troposphere to become moister and dry regions to become drier, and if horizontal mixing of moisture is not rapid enough to overcome this tendency, then the atmosphere will tend to separate into increasingly large moist and dry regions through a process of coarsening. We present a simple model for the moisture budget of the free troposphere, including subsidence drying, convective moistening, and horizontal mixing, and a constraint on total precipitation representing radiative-convective equilibrium. When initialized with a spatially uncorrelated moisture distribution, the model shows self-organization of precipitation with two main stages: A coarsening stage where the correlation length grows proportional to time to the power 1/2 and a droplet stage where precipitation is confined to a decreasing number of circular moist regions. A potential function is introduced to characterize the tendency for self-organization, which could be a useful diagnostic for analyzing cloud-resolving model simulations.