Drop‐size distribution in cloud and fog

Experimental data relating to drop‐size distribution in cloud and fog are examined and it is shown that in many cases the size distribution can be represented by the formula where F is the fraction of liquid water in the air comprised by drops with diameter less than x. The constant a increases with the liquid water content of the cloud. It is not clear what governs the value of the constant n but a reasonable mean value is about 3.3.

It is shown that, if the drop‐size distribution can be described by the equation quoted above the median volume diameter is the most suitable parameter for describing the average size of the cloud particles when the value of n is not known.