A Wind Tunnel and Theoretical Study of the Melting Behavior of Atmospheric Ice Particles. I: A Wind Tunnel Study of Frozen Drops of Radius < 500 μm

Abstract

A study has been made on the melting behavior of frozen drops suspended freely at terminal velocity in the UCLA Cloud Tunnel. The relative humidity of the air ranged between 25 and 95%. The warming rates of the tunnel air stream ranged from 2 to 5°C min?1, which for the studied ice particles of radius between 200 and 500 ?m, corresponded to warming rates of 0.8 to 5.2°C per 100 m of fall. The rate of melting of the frozen drops and their fall behavior during melting were continually monitored by motion picture. From these observations the dimensions of the ice core inside the melting drop was determined as a function of time, and from the latter the total melting time was found. The present wind tunnel observations were compared with the theoretical predictions of Mason (1956). Considerable disagreement with Mason's theory was found. This disagreement was attributed to the pronounced asymmetric melting and the internal circulation in the melt water, both of which were disregarded in Mason's theory.