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<br />"seeding with silver iodide from ground generators <br />upwind of the Tushar Mountains near Beaver, Utah <br />will increase the number of ice crystals within <br />the supercooled regions of wintertime clouds over <br />the mountains. It is hypothesized that these ice <br />crystals will grow by vapor diffusion and by <br />riming, at the expense of the supercooled water in <br />the cloud, and will fall through the clouds with <br />trajectories which carry them onto the mountain <br />slopes. If this hypothesis is true, the effect of <br />the seeding is to increase the amount of snow from <br />the clouds and their precipitation efficiency." <br />The hypothesis as stated here specifically refers to the Tushar Mtns <br />but, in fact, is applied wherever there is seeding of winter clouds <br />over mountains in Utah. <br />The hypothesis assumes there are regions of supercooled liquid <br />water in the clouds, that silver iodide released at the ground is <br />transported to these regions, that additional ice crystals will be <br />produced by the seeding, that the crystals will grow by diffusion <br />and riming and consume some of the supercooled liquid water, that <br />these growing particles will fall along trajectories terminating on <br />the mountain slopes, and that there will then be an increase in the <br />precipitation efficiency of the clouds. The overall purpose of the <br />1987 research program was to examine the validity of these assump- <br />tions and, if and where necessary, develop improved assumptions. <br />The net result will be a better seeding hypothesis. From this <br />overall purpose of the 1987 research program the major objectives <br /> <br />4 <br />