WMOD00298

• Title: Quantifying Ice Nucleation by Silver Iodide Aerosols
• Date: 5/1/1990
• State: CO
• Weather Modification - Doc Type: Report

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ABSTRACT

QUANTIFYING ICE NUCLEATION BY SILVER IODIDE AEROSOLS

Laboratory studies of artificial ice nucleating aerosols used for

weather modification by cloud seeding have generally been inadequate

for describing their complex action in the varied temperature, pressure

humidity, and cloud conditions that can be encountered in the

atmosphere. This study provides a quantitative framework for predicting

ice formation by aerosol particles based on experiments which

specifically target currently accepted mechanisms by which ice can

form. A physical system for reproducing realistic atmospheric cloud

conditions, the Colorado State University dynamic (controlled

expansion) cloud chamber, is described. Physical simulations of

adiabatic cloud formation and growth are demonstrated. Methodologies

were also formulated to use the cloud chamber and other available

intrumentation to isolate the action of ice nucleating aerosols by

accepted primary ice nucleation modes. These methods were applied to

the study of two chemically different silver iodide (AgI)-type

aerosols, generated in the exact form in which they have been used for

seeding natural clouds. The results were formulated as a function of

bas ic thermodynamic quanti ties and particle size. An available one

dimensional numerical cloud model with microphysical detail was adapted

for the equivalent simulation of experiments performed in the cloud

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