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

18

(LeL). ice crystal production was prolonaed, ach1ev1ns a maximum at a
temperature of -300C. When the aerosol are introduced intooloudy air,
cooler than the LCL, nuoleation oooured more rapidly, achieving a
maximum at a temperature of -220C. for the same rate of cooling of the
previous experiment.
The work of Chen, et ale (1972) has shown that the rate of chemical
reaction is the controlling prooess in the transformations that occur in
the All-Hal-H20 system. The rates of chemical reaction (hydration and
break up of the Agl-Nal-water complex) observed are oomparable in seale
to many of the rates of ioe orystal produotion observed by Smith and
Heffernan (1'54), Edwards and Evans (1960). Warburton and Heffernan
(1964), Davis and Steele (1'68), and Garvey, et ale (1976).
2.1.4(:~teot of Water Supersaturation on Ice Nucleation by AgI-NaI\
The effect of excess water vapor concentration or supersaturation
with respect to a plane water surfaoe on the properties of condensation
nuclei has been investigated (see, for example, Pruppaoher and Klett,
1'78,p. 225-241). COmparatively little work. however, has been done on
the relationship of water supersaturation and ice nuoleating properties
ot hygroscopio ioe nuclei such as 2Agl'Nal containing aerosol particles.
A full speotrum of number of ioe nuclei or yield versus supersaturation
tor any aerosol which oontains Aglis lacking. The type of data
available that describes trends in the ice nucleating behavior of
hygroscopic ice nuclei are those in whioh qualitatively high water
supersaturations were used in mixing cloud chamber tests (Edwards and
Evans. 1960, and Mossop, 1968). Other research dealt with the effect of
preconditioning the aerosol with high water vapor ooncentrations prior
to making ice nucleation observations (St. Louis and Steele, 1968).

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I