Observations of Diffusional Ice Crystal Growth in Clouds

Abstract

The observed size of ice crystals obtained by sampling in Formvar is compared to the theoretical size an ice crystal should attain when growing by diffusion. The variables which are not fixed by environmental conditions are adjusted for the best fit. For reasonable values of these parameters the agreement between observation and calculation is good, except in the case where phloroglucinol was the nucleating agent. The sizes of the ice crystals sampled after the same apparent time and under the same growth conditions varied over a range of 4 to 1; this range is discussed. The observations, all in natural cloud conditions, are not in complete accord with diffusional growth. The differences are discussed with respect to weather modification.