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<br />ABSTRACT <br /> <br />This report presents the findings of an investigation into the changes <br /> <br />expected in ice crystal characteristics caused by silver iodide seeding <br /> <br />of winter, orographic clouds in the San Juan Mountains of Colorado. Ice <br /> <br />crystal data were collected from 22 storms near Wolf Creek Pass for the <br /> <br />period of February, 1973 through March, 1975. Additional data on ice <br /> <br />nuclei and cloud top temperature were also obtained for the period. <br /> <br />Analyses were performed on the crystal type, size, concentration, and <br /> <br />/ <br />/ <br /> <br />the amount of rime under seeded and natural conditions. <br /> <br />The storms were. <br />.- .-=--~ <br /> <br />subdivided into three-hour blocks based on sounding times. Each block <br /> <br />was classified into a seed or nonseed category depending on generator I <br />/ <br />operations and ice nucleus concentrations. A total of 66 three-hour <br /> <br />blocks was studied. <br /> <br />/ <br />, <br /> <br />/ <br />/ <br />I <br />Changes in ice crystal characteristics were observed near Wolf 'Creek Pass <br />I <br />/ <br />when artificial nuclei were detected in and slightly upwind or the target <br />/ <br /> <br />area. Precipitation and ice crystal concentrations were ipcreased and <br /> <br />riming was decreased as expected. Relative concentrations of plates and <br /> <br />columns were increased. Crystal diameter was increased against expectation. <br /> <br />Ice crystal concentration measured at KP3; did not appear to be a function <br /> <br />of cloud-top temperature for either seeded or nonseeded cases. However, <br /> <br />seeding did increase the crystal concentration at all temperatures. <br /> <br />. ! <br /> <br />/' <br /> <br />if <br />/ <br />