On the Collection Efficiency of Snow Crystals for Cloud Droplets

Abstract

The collection efficiency of circular disks, hexagonal plates and plates with broad branches simulated to snow crystals for water droplets was experimentally obtained. The capture of supercooled droplets by the models of snow crystals was examined in the free falling state of them through a layer of droplets in order to make the experiment analogous to natural condition. The collection efficiency of natural snow crystals of hexagonal plate type was also obtained by the same method.
The collection efficiencies of models were generally smaller than Ranz and Wong's theoretical value based on the assumption of simplified flow around the circular disk except the region of their dimensionless parameter Ψ_??_0.9, where Ψ is a measure of the inertia of droplets. In the region of Ψ_??_1/16, where the theoretical collection efficiency of circular disk becomes zero, experimental values were finite.
The collection efficiencies of natural snow crystals were smaller than values of models in the region of Ψ>0.3.