WMOD00298

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

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expected size effects for nucleation. Experiments were also performed

with the full polydisperse particle size distributions for comparison.

Comparisons made between cloud chamber experiments and numerical

model simulations were made "equivalent" in the sense that temperature,

pressure, humidity and ascent rate were identical. Cloud condensation

nuclei activity was controlled in the laboratory experiments and

specified in the model simulations. Items which were not simulated were

considered to be of secondary importance in these experiments. They

include turbulent mixing, interactions with precipitation size
particles, radiation effects, and electric field and particle charging

effects. Additionally, some aspects related to the long term residence

of ice nuclei in the atmosphere, namely photodeactivation and potential

reactivation following evaporation, were not studied.

Comparative field experimental data were obtained from

tracer/seeding experiments conducted in North Dakota cumulus clouds

(Stith et al., 1990). These experiments used AgI-AgCl aerosols.

Specific experimental plans are outlined in chapter 4, and are
discussed further in Chapter 5.

1.4 Expected Utility of Results

The results of this research should have a number of applications,

as enumerated here.

1. It is important to compare laboratory experiments and computer

model simulations and to evaluate how well the results can be

extrapolated to real atmospheric situations. The results from

this work should provide a more valid description of the early