The Size Distribution of Cumulus Clouds in Representative Florida Populations

The cumulus cloud populations of the Florida peninsula were photographed periodically and comprehensively on 19 days in August and September 1957, using multiple, high-flying aircraft. Particular sets of these photographs, called population samples, were selected which showed representative examples of the cumulus populations of customary, widespread occurrence of the various days and hours. These were analyzed to determine the size distribution characteristics of the cumuli and the time trends. The analyses revealed 1) that the number density of the cumuli decreased nearly exponentially with increasing cloud-size, 2) that a definite maximum-size-class of the cumuli existed in the populations, which increased in size diurnally in a regular fashion, 3) that there was considerable variance, both within single populations and with the time of day, in the relationships of the vertical and horizontal dimensions of the clouds, 4) that particular modal classes of the cumuli, of intermediate size, existed in the populations which were the primary contributors to the population sky cover and cloudy volume, and 5) that group structures occurred in the populations which began forming noticeably about mid-morning and which were an important developmental feature of the cumulus convection. The equations of a cumulus population model were developed on the results of the Florida sampling.These equations were employed to facilitate comparisons of the Florida data with other population data previously reported by Blackmer and Serebreny. They were also applied in other ways, as are pointed out.