An Efficient, Fast Functioning Nucleating Agent -- AgI'AgCl-4NaCl

Abstract

A composite ice nucleus aerosol, AglCI-4NaCI, has been generated and characterized for nucleation efficiencies, rates of ice crystal formation, and mechanisms of nucleation, under water saturation and transient supersaturation conditions. The addition of NaCl to the highly efficient contact nucleus, AgI(0.8)-Cl(0.2) changed the nucleation mechanism to condensation-freezing at water saturation and increased the rates of ice crystal formation dramaticaily, while retaining the high efficiency of the AgICl nucleus aerosol. Under transient supersaturation conditions, this new aerosol demonstrated improved ice nucleation efficiencies at T > -12 C, and even faster ice crystal formation rates, suggesting a change of nucleation mechanism to forced condensation-freezing. This ice nucleation aerosol should be advantageous for use in weather modification field programs under conditions where low cloud droplet concentrations suggest the use of a condensation-freezing nucleant.