Scavenging of Atmospheric Particles by Ice Crystals

Ice crystals growing in supercooled clouds were studied in a Nakaya chamber to determine their ability to include foreign particles in their structure. In a series of experiments on wash-out ratios of condensing water and growing ice, ice crystals proved to be 16 times more efficient than water in capturing atmospheric particles. The existence of Facy's “dust-free space” around evaporating surfaces was confirmed. The dust-free space around supercooled droplets is considered, in connection with Stefan flow, to be an important mechanism in bringing particles toward ice surfaces, and may account for the observed wash-out efficiency of ice crystals.