WMOD00300

• Title: Characterization of Silver Iodide-Sodium Iodide Ice Nuclei Using Chemical Kinetic Methodology
• Date: 5/1/1985
• State: CO
• Weather Modification - Doc Type: Report

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significantly change with temperature. The AgI aerosol Vonnegut used
was later shown to nucleate ice primarily by a mechanism controlled by

Brownian coalescence of aerosol particles with cloud droplets (DeMott,
et al., 1983).

The rate of ice crystal production by 2AgI"NaI aerosol particles
was measured by Smith and Heffernan (1954)" The observed rate was
exponential with time and required about 12 minutes for complete
nucleation at -160C. A oonversion tactor was defined as the ratio of
the total number of ice orystals produced at the end of a run to the
number of ice crystals observed in the tirst I11nute. The conversion
tactor approaches one as the rate inoreases. Conversion tactors from
-SoC to -2SoC indicate that the rate of ice nucleation increased with

decreasing temperature. 110 explanation was given by the autbQrs for
this behavior. Variation of rate with temperature was presented
indirectly by Davis and Steele (1968). They introduced tbe parameter

'effective nuclei per minute' tor several nucleants at different

temperatures. For AgI-RaI aerosol particles from acetone solution

oombustion, the etfective nuclei per I11nute, or rate, increases

exponentially with decreasing temperature, in agreement with Warburton
and Heffernan (1964).

The half life (time required for ioe crystal tallout rate to
decrease to lIe of its initial value) for AgI aerosol particles produced
from the NEITB-1 pyrotecbnic flare at temperatures above -200C is given
by Garvey, et ale (1'76). These aerosol particles are bygroscopic (W.
Finnegan, personal cClDlllunication) and are similar to AgI-NaI aerosol.
The balf lives reported decrease with decreasing temperature, indicating
Other
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