Accession Number : AD0616625

Title :   TIME-DEPENDENT CHARACTERISTICS OF THE HETEROGENEOUS NUCLEATION OF ICE,

Corporate Author : MCGILL UNIV MONTREAL (QUEBEC) STORMY WEATHER GROUP

Personal Author(s) : Vali,Gabor ; stansbury,E. J.

Report Date : APR 1965

Pagination or Media Count : 59

Abstract : The dependence of heterogeneous nucleation of supercooled water drops on temperature and the duration of supercooling has been studied. The rain-sized drops were placed on an oiled aluminium surface and thermoelectric refrigeration was used to provide constant cooling-rates and to maintain constant temperatures. Once-distilled tap-water and melted snow and hail were investigated. Only the first two of these showed definite time-dependent properties. The experimental results are inconsistent with the hypothesis that all drops have equal probability of nucleation (stochastic hypothesis), and also with the hypothesis that the freezing temperature of a drop is the characteristic temperature of one of the impurities contained in the drop (''singular'' hypothesis). The results can be explained if the existence of a variety of nuclei is recognized, each of which is most likely to cause nucleation in a different range of temperatures, and if the nucleation probability associated with each impurity is a function of the temperature of the sample. (Author)

Descriptors :   (*ICE, NUCLEATION), TIME, SUPERCOOLING, WATER, FREEZING, HAIL, SNOW, ATMOSPHERIC PRECIPITATION, TEMPERATURE

Distribution Statement : APPROVED FOR PUBLIC RELEASE