The Influence of Environmental Parameters on the Freezing and Fragmentation of Suspended Water Drops

Abstract

The fragmentation of freezing water droplets in natural clouds has been postulated by several workers, and this phenomenon has been observed in numerous laboratory investigations. However, the profound effect that environmental conditions can have on fragmentation has not been fully appreciated. In the first part of this paper the factors that might affect the freezing behavior and fragmentation of a water drop are discussed, and, where possible, are analyzed in detail. In the second part of the paper results are presented of laboratory experiments on the freezing of suspended water drops 1 mm in diameter. Drops nucleated in air under equilibrium conditions were never observed to shatter and only one drop in ten ejected an ice splinter. The shattering and large splinter counts from suspended drops nucleated in air which have been reported by other workers are attributed to the contamination of the drops by carbon dioxide and nucleation under non-equilibrium conditions. Drops frozen in hydrogen shattered frequently if the temperature was lower than ?9C. Drops frozen in helium at ?10 to ?12C shattered on occasions. In a mixture of air and carbon dioxide the shattering behavior was very dependent on the concentration of carbon dioxide. Large numbers of ice splinters were detected only if a drop shattered.