Physics Commons^™

The Texture Of Clouds, A. R. Jameson, Alexander Kostinski, R A. Black

Department of Physics Publications

Using a precise definition of clustering, it is shown that in two tropical cumulus clouds, droplets appear to be bunched over distances ranging from at least a kilometer or more down to several centimeters. A statistical framework is proposed for quantifying clustering in terms of a Poisson probability mixture. While these observations require further substantiation in many different clouds, droplet clustering may play a role in diverse phenomena from the coalescence growth of raindrops to the scattering of radiation by clouds.

Fluctuation Properties Of Precipitation. Part Ii: Reconsideration Of The Meaning And Measurement Of Raindrop Size Distributions, A. R. Jameson, Alexander Kostinski

Department of Physics Publications

For M drop size categories, rain is frequently viewed simply as the superposition of M,statistically independent Poisson-distributed drop fluxes each described by its own mean concentration. Implicit in such a Poissonian model is the assumption of uncorrelated counts among the drops. However, it is well known that drop size distributions are the result of the processes of collision, coalescence, and breakup, which should lead to correlations.

This inconsistency is resolved in this work. Using 1-min disdrometer measurements, two-point cross-correlation functions are used to show that drop counts at different sizes are correlated rather than independent. Moreover, it is argued …