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<br />Feng, D., and W. G. Finnegan, 1989: An efficient, fast-functioning nucleating agent-AgI 'AgCI-4NaCI.
<br />Journal of Weather Modification, 21:41-45.
<br />
<br />A composite ice nucleus aerosol, AgICI-4NaCl, has been generated and characterized for nucleation
<br />efficiencies, rates of ice crystal fonnation, and mechanisms of nucleation, under water saturation and
<br />transient supersaturation conditions. The addition of NaCl to the highly efficient contact nucleus,
<br />Aglo.sCIo,2' changed the nucleation mechanism to condensation-freezing at water saturation and
<br />increased the rates of ice crystal fonnation dramatically, while retaining the high efficiency of the AgICl
<br />nucleus aerosol. Under transient supersaturation conditions, this new aerosol demonstrated improved
<br />ice nucleation efficiencies at T > -120C, and even faster ice crystal fonnation rates, suggesting a change
<br />of nucleation mechanism to forced condensation-freezing. This ice nucleation aerosol should be
<br />advantageous for use in weather modification field programs under conditions where low cloud droplet
<br />concentrations suggest the use of a condensation-freezing nucleant.
<br />
<br />Finnegan, W. G., and R. L. Pitter, 1991: Chemical reactions in growing snowflakes. Poster presentation,
<br />Annual Meeting of the AAAS, Washington, DC, February 14-19, 1991. American Association for
<br />the Advancement of Science, Washington, DC.
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<br />No abstract.
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<br />Finnegan, W. G., and R. L. Pitter, 1991: Comments on "The persistence of seeding effects in a winter
<br />orographic cloud seeded with silver iodide burned in acetone." Journal of Applied Meteorology,
<br />30:903-904.
<br />
<br />The article by Deshler and Reynolds (1990) contains errors and misconceptions concerning the
<br />chemistry, generation, characterization, and functioning mechanisms of silver iodide-containing ice
<br />nucleus aerosols. These errors may be due in part either to the authors not understanding the processes
<br />of ice nucleation and ice cryst.'ll fonnation, which are critical aspects of cold cloud modification, or to
<br />their careless use of jargon. In this Comment, only the errors in Deshler and Reynolds (1990) relevant
<br />to ice fonnation are discussed.
<br />
<br />Finnegan, W. G., R. L. Pitter, and L. G. Young, 1991: Preliminary study of coupled oxidation-reduction
<br />reactions of included ions in growing ice crystals. Atmospheric Environment, 25A:2531-2534.
<br />
<br />Cloud chamber studies have demonstrated coupled oxidation-reduction reactions of included ions in
<br />free-falling ice crystals growing in a supercooled liquid water cloud. These reactions are hypothesized
<br />to occur as a consequence of preferential ion separations which take place at the interface between
<br />growing ice and the liquid layer at the growing crystal surfaces, followed by electron transfers to
<br />establish system neutrality. Oxidations of sulfide ion to sulfate ion and of halide ions to higher valence
<br />species have been documented. Reductions of silver ion to metallic silver and of sulfate ion to lower
<br />valence species have also been documented in systems of appropriate ion compositions. Similar
<br />reactions have been reported to occur during the freezing of bulk dilute solutions of ammonium and/or
<br />halide salts.
<br />
<br />Finnegml, W. G., an.d R. L. Pitter, 1990: Ice crystal breeding: A primary nucleation mechanism. Nucleation
<br />Symposium, Bethlehem, PA, June 18-20, 1990. American Chemical Society, Washington, DC, 114.
<br />
<br />No abstract.
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