WMOD00298

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

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5

models; to provide information for direct comparison of laboratory and

model results with atmospheric clouds; and to provide information for

planning cloud seeding research and operations.

These general objectives can be separated into seven specific

objectives for this research. These are:

1. Define and demonstrate appropriate experiments for using a

continuous expansion cloud chamber and other available tools to

assess the separate and combined roles of the four hypothesized

primary modes of ice nucleation (deposition, condensation-

freezing, immersion-freezing, and contact-freezing, as defined in

Chapter 4) for any ice nucleating aerosol.

2. Using defined experimental methods, determine the efficiencies,

nucleation rates and mechanisms of two commonly used, chemically

different ice nucleating aerosols, as they relate to cloud

temperature, supersaturation and droplet concentration. The

effect that condensation temperature and parcel history of

temperature and humidity have on the nucleation modes,

efficiencies and rates are also assessed.

3. Perform numerical cloud model simulations using the same

initialization criteria and expansion rates as cloud chamber

experiments. An existing detailed microphysical model (Young
1974a) is used. Areas where current descriptions of artificial

ice nuclei function are unsatisfactory are identified, based on

comparing the model results with those from the cloud chamber.