Theoretical aspects of the size distribution of fog particles

Abstract Following some very interesting work by Houghton and Radford on the determination of size distribution of drops in fogs and clouds, a theory is here presented to account for the experimental results obtained. The basis of the theory is that due to Brownian movement, to turbulence, and to the influence of gravity, collisions between the drops take place and thet upon collision coalescence results. There will thus be a gradual increase in the average size of the drops consutling the fog due to these collisions, and the problem with which one is confornted is to detemine what the resultant size distribution of the drops will be. In a simple case, where it is assumed that the frequency of distribution curve. The result thus obtained shows very satisfactory agreement with the experimental values given by Houghton and Radford. It has also been found possible to obtain an approximate theoretical value for the rate of growth of the “most preferred” drop sizes, but it would appear that in nature the rate of growth is several times more rapid than the theoretical value. The theory might prove useful in showing how research should be directed in order to arrive at a full understanding of the mechanism by which fogs and clouds are formed.