On the Collecting Efficiency of Cloud Particles by Snow Crystals

Abstract

Cloud droplets collected on snow crystals were observed by means of microscopic photograph method simultaneously with the measurement of size distribution of cloud particles which were suspended in free air at the top of Mt. Teine, Hokkaido in the winter seasons of 1959, 60 and 61. The falling path of snow crystals of various types ware estimated by the use of the vertical profile of air temperature and humidity and by the use of Nakaya's Ta-s diagram. The mean density and size distribution of cloud particles in the cloud through which the particles fell were assumed to be uniform with those which were observed at the mountain.From the data measured, following conclusions were reached : 1) The size distribution of cloud droplets collected on snow crystals always was larger than that in the free air.2) The efficiency of collection of cloud particles by snow crystals seemed to be much smaller than that calculated by Langmuir method.3) snow crystals of needle type showed fairly good efficiency of collection.The discrepancy in the collecting efficiency is considered to be due to the fact that the size distribution was not observed throughout a whole cloud layer but only near the cloud base.