Some Aspects of Rain Formation in Warm Cloud (I) Salinity of Individual Raindrops and Other Quantities concerning Rainfall

Abstract

Calculations of droplet growth are made based on a model of cloud, through the cloud base of which upward current does not enter. If raindrops form on large sea-salt particles in this cloud, it can be shown that the larger raindrops form on the larger sea-salt particles. Using this model of cloud, functional relations are presented between the size distribution of large sea-salt particles and various quantities concerning the rainfall from a warm cloud.
The rainfall intensity, the flux density distribution of raindrops with respect to radius, the salinity of rain water in bulk, and the salinity of individual raindrops are deduced. The function expressing the salinity of raindrops is found to have a minimum at a certain radius. This may be considered to show one of the tentative explanations for the appearance of minimum value of raindrop salinity found by Turner (1955) in the case of warm rains. Derived raindrop spectrum changes with rainfall intensity in a manner for some aspects resembling that found by Blanchard (1953) in Hawaii.
The present calculations seem to be useful to some extent for quantitative estimations on some features of rainfall from orographic warm clouds.