Raindrop Size Distribution with Collision Breakup in an Axisymmetric Warm Cloud Model

Abstract

Abstract The effect of the collision breakup process, as described by McTaggart-Cowan and List (1975), on the raindrop size distribution and rainfall intensity in warm clouds was studied using an axisymmetric cloud model (Takahashi, 1977). The cloud model demonstrates that with collision breakup the raindrop concentration decreases sharply in the large raindrop size range and exhibits a pronounced secondary maximum, at a drop size defined as the “peak drop” size, within the normal raindrop size range. The concentration at the peak raindrop size is consistent with that measured in natural warm cloud rainfall, and is much larger than the concentration obtained from computer simulations which do not include the collision breakup process.