BREAKUP OF LEVITATED FROST PARTICLES

We have studied the sublimation and breakup of single 100-200 mu m fro st particles levitated electrically at temperatures in the range -2 de grees C to -30 degrees C. Breakup rates were largely independent of te mperature and humidity in this range but strongly dependent on particl e shape. Irregular particles of high aspect ratio were most likely to break up. Sublimation (evaporation) was accompanied by an increasing a spect ratio. A linearized sublimation model, presented in the appendix , accounts for the observation that thin neck regions were not subject to enhanced sublimation rates. Estimates of the forces involved in br eakup suggest that the breaking strength of these frost particles is c onsiderably less than that of bulk ice. We discuss possible implicatio ns of our results for ice particle multiplication in clouds.