A New Look at Homogeneous Ice Nucleation in Supercooled Water Drops

Abstract

The classical theory for homogeneous ice nucleation in supercooled water is investigated in the light of recent data published in various physico-chemical journal on the physical properties of supercooled water and in the light of recent evidence that the cooperative nature of the hydrogen bonds between water molecules is responsible for a singularity behavior of pure supercooled water at ?45°C. Recent rates for homogeneous ice nucleation in supercooled water drops field from field experiments at the cirrus cloud level and from cloud chamber studies were shown to be quantitatively in agreement with the laboratory-derived lowest temperatures to which ultrapure water drops of a given size have been supercooled. Using these verified nucleation rates together with the recent physical property data for supercooled water, the activation energy for the transfer of water molecules across the ice-water interface was computed using the classical nucleation rate equation. The thus computed values are significantly different from earlier values that were based on the activation energy for viscous flow but are consistent with present knowledge of structure of supercooled water. The present results eliminate the earlier discrepancies that existed between the results of the classical nucleation equation, the field and laboratory data, and the results from the molecular model of Eadie.