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<br />. <br /> <br />. <br /> <br />e <br /> <br />CHAPTER I <br /> <br />. <br /> <br />INTRODUCTION <br /> <br />. <br /> <br />A theoretical basis for artificial modification of <br /> <br /> <br />precipitation fran clouds was put forth by Bergeron (1933) based <br /> <br />on the coexistence of ke crystals and supercooled droplets. He <br /> <br />stated that "The vapor tension will adjust itself to a value In <br /> <br /> <br />between the saturation values over ice and water. The effect of <br /> <br /> <br />this must be that condensation will take place continually on the <br /> <br /> <br />ice, whereas at the same time liquid water evaporates, and this <br /> <br />process must go on until the liquid phase is entirely consumed". <br /> <br /> <br />Findeisen (1938) expandE:rl Bergeron's ideas considering the manner <br /> <br /> <br />in which ice crystals could form, favoring direct crystallization <br /> <br /> <br />from vapor (subl imation) in preference to freezing of droplets. <br /> <br /> <br />Findeisen foresaw the possibility of initiating the mechanism by <br /> <br /> <br />introducing sui table nuclei. Based on the ideas of Bergeron and <br /> <br /> <br />Findeisen, Schaefer (JL946) conducted the first experiments with <br /> <br /> <br />dry ice which sowed the seeds for modern weather modification <br /> <br />technology. <br /> <br /> <br />Schaefer's exper iments showed promising results which led to <br /> <br />many projects to study the effects of seeding real clouds. <br /> <br />"project Cirrus" supported by the General Electric Company was <br /> <br />launched in 1947. The most pronounced effect produced by this <br /> <br />. <br /> <br />.e <br /> <br />-e <br /> <br />. <br /> <br />. <br /> <br />;e <br />. <br /> <br />. <br />