Precipitation Streaks and Raindrop Size-distributions

Abstract

An analysis is made of a continuous record of raindrop sizedistributions, obtained at the ground, and an explanation is given in terms of the theory of precipitation streak. The maxima and the minima of the space concentrations for large drops preceded those for smaller drops. The observed time-lags agree well with those computed from upper-wind data, except for very small drops. From the observed surface distributions, an attempt is made to deduce probable size-distributions in the generating cell. Considering the effects of evaporation and collision during fall, and also an effect resulting from the drop-counting technique, in which drops are classified by size, the size distributions of raindrops in the generating cell are presumed to be very narrow, with many small drops and few large drops, compared with those usually observed at ground level in a continuous rain. They are very similar to those obtained by BLANCHARD (1953) in Hawaiian orographic rain-clouds.