An Exploratory Study of Ice Nucleation by Soot Aerosols

Abstract
The activities of nearly monodisperse soot particles as ice nuclei at temperatures below −20°C were examined in a short series of experiments. A continuous slow expansion cloud chamber was used to cause cloud formation and growth on soot during simulations of adiabatic cooling by expansion. Soot was generated using an acetylene burner operating near the sooting limit. Activity as ice nuclei was measured as clouds cooled to the apparent homogeneous-freezing temperatures of the cloud droplets. Immersion-freezing nucleation appears to be a particularly dominant heterogeneous mode for these particles. The preliminary results suggest that activity by immersion-freezing increases with particle size. Abstract The activities of nearly monodisperse soot particles as ice nuclei at temperatures below −20°C were examined in a short series of experiments. A continuous slow expansion cloud chamber was used to cause cloud formation and growth on soot during simulations of adiabatic cooling by expansion. Soot was generated using an acetylene burner operating near the sooting limit. Activity as ice nuclei was measured as clouds cooled to the apparent homogeneous-freezing temperatures of the cloud droplets. Immersion-freezing nucleation appears to be a particularly dominant heterogeneous mode for these particles. The preliminary results suggest that activity by immersion-freezing increases with particle size.