Equilibrium Raindrop Size Distributions in Tropical Rain

Observations of raindrop size distributions in Brazil were analyzed. For long lasting records and during periods when there was no evidence of rain falling through updraft, the observations indicate that equilibrium between the coalescence and the breakup processes leads to a generic shape of the distribution such that distributions for different rain rates are proportional to each other. This is in agreement with numerical solutions to the stochastic equation. In cases where there is indication that updraft was present, the drop size distributions were markedly different. The proportionality between distributions is observed in these cases as well.