Experimental Studies on the Growth of Small Ice Crystals

Abstract

The fall velocities and growth rates of freely falling ice crystals were measured at various intervals for about 1 min after ice crystal nucleation of a supercooled fog. Measurements were also made at various degrees of supercooling. The results showed that: 1) the velocity varied linearly with time t for 60 sec after the first 12-sec period, with two falling velocity plateaus being found at ?5 and ?8, and ?10 and ?18C; 2) the mass varied as t1/2 except at ?18 to ?19C, a small mass growth rate peak being found at ?6.5C; 3) the larger peak shifted toward colder regions as the crystal grew; 4? tsuzumi crystals formed at around ?18C; and 5) at the temperatures where two maxima of the mass growth occurred, the apparent densities were at minima. Current theory failed to describe the mass growth rate of ice crystals. The existence of an unknown factor was detected and introduced into the rate equation of ice crystal growth.