Field and Laboratory Observations of Ice Crystal Growth from the Vapor

Abstract

Abstract The temperature dependence of the habit of ice crystals growing in a water vapor diffusion chamber is related to the growth rate of ice crystals in a supercooled cloud. The rates of growth occurring between −4 and −6C as needles or between −12 and −16C as dendrites may be in excess of those at intermediate temperatures by as much as a factor of 100. The effect of seeding a supercooled cloud will therefore depend critically on its temperature. Growth of crystals at large supersaturation between −4 and −6C takes place as spikes growing along a direction 25° to the c axis. These crystals have been observed in the diffusion chamber, and also as frost near hot springs in Yellowstone Park. The molecular processes responsible for these habit changes are discussed.