Lognormal cloud-size distribution
From AMS Glossary
lognormal cloud-size distribution
The logarithm of cumulus cloud diameters and cloud thicknesses is normally (Gaussian) distributed, according to many observations.
where x is cloud size, Δx is a small range of cloud sizes (i.e., bin width), f(x) is the fraction of clouds with sizes between x - 0.5Δx and x + 0.5Δx, Lx is a location parameter, and sx is a dimensionless spread parameter.
Stull, R. B. 1995. Meteorology Today for Scientists and Engineers. 385 pp.