Some Observations Suggesting Ice Multiplication in the Atmosphere

Abstract

Data on the composition of stratocumulus and nimbostratus clouds having temperatures warmer than ?9C reveal, in some instances, high concentrations of ice particles (to approximately 400 liter?1 of cloud). On the basis of measurements of the concentration of ice-forming nuclei reported in the literature, it is concluded that some multiplication process was responsible for the observed concentrations of ice particles. Since moderately large drops were present in the glaciating clouds, the data are consistent with a process whereby drops are frozen and splintered; however, in view of other evidence casting doubt on the validity of this process in the free atmosphere, alternative hypotheses are examined. Freezing of drops by a stochastic process is untenable, but a mechanical fracturing process seems possible and merits additional study.