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<br />14 <br /> <br />8upersaturations resulted in hi&her yields tor both hygrosoopic and <br /> <br />bydrophobic AgI aerosol particles. <br />The results of Davis and Steele (1968) should be compared to those <br /> <br />of Garvey (1975) (Fig. 1). Both investigators used the isothermal cloud <br /> <br />~,~~ber at,,~~~orado S~.a~~.Yni V.rlj.ty:, The 960 liter ch8llber was <br />subjected to major alterations to improve its perf()rma~()e"~lg_.~..t,)Q,Y'LI.~J.2... <br />, ,..,>-..."".;".."",~,,,,,.,,..<,o.,. ,,,,,,,""'F..'r.,,",''';''''''''-'''''~'''"; .vic_-,,__} ',co "i_.~..,.."",.,il~~'.'-"";;:'''>O'"'''' ~~h""'.-',_-, -'''','' - - <br /> <br />Tbe most important of these changes was the provision for supplying <br />pre-cooled cloud air near the top of the chamber. This assured <br />temperature and cloud density uniformity throughout the chamber volume. <br /> <br />Prior to 1970, warm cloud air was introduced into the subzero degree <br /> <br />ohamber and large water supersaturations and temperature gradients <br /> <br />resulted. As in the work of Warburton and Beffernan (1964) yield <br />measured by Davis and Steele (1968) was bi&h at cold temperatures. <br /> <br />Subsequent elimination of supersaturations and temperature gradients <br /> <br />greatly reduced tbe yield for a given generator (Garvey, 1975). The <br />yield at -20oC for the North American generator burning AgI-Nal-aoetone, <br />was reduced from 311016gm-1 to 311015gm-1 (Fig. 1). <br />Edwards and Evans (1960) assuaed that the ioe nuclei they examined <br /> <br />was pure, hydropbobic AgI. In semi-quantitative tests wbere their <br /> <br />aerosol was compared with aerosol containing AgI-NaI produced from <br />acetone solution combustion, Edwards and Evans <19(0) found both <br /> <br />aerosols functioned in the same manner. It is questionable tbat the AgI <br /> <br />used in their tests was hydrophobic due to possible contamination of the <br /> <br />AgI. The number of sublimation (deposition) nuclei which functioned at <br />9ft relative humidity at any temperature was less than 0.5't of the <br /> <br />number which functioned at water saturation, indicating that water <br /> <br />saturation and hence droplet formation was a neoessary step in the <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />