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<br />177 <br /> <br />figure 6.3. Only the seeded portions persisted longer than <br /> <br />one-half minute or so. The seeded portions appeared to be <br /> <br /> <br />much denser. They probably contained a higher particle <br /> <br /> <br />density. Diffusion of the seeded clouds appeared to be slow <br /> <br /> <br />compared to observations of jet aircraft contrails and the <br /> <br /> <br />initial cloud trail was narrower. The wake of the Schweizer <br /> <br /> <br />probably contains much less moisture and turbulent energy <br /> <br /> <br />which leads to a smal1er initial trail and slower initial <br /> <br /> <br />dispersion rate than for jet aircraft contrails. <br />Since within 5 to 15 minutes the seeded clouds were <br /> <br /> <br />carried into dry regions by the flow through the usual wave <br /> <br /> <br />patterns, little data on the long term behavior of the <br /> <br /> <br />seeded clouds could be obtained. Seeding was never carried <br /> <br /> <br />out in completely clear skies, as the genera 1 wave activity <br /> <br /> <br />produced clouds in at least some areas if sufficient moisture <br /> <br /> <br />was present for our operations. Attempts to 100k for develop- <br /> <br /> <br />ment of clouds downstream from the seeding area, which might <br /> <br /> <br />have resulted from dispersed seeding material, in DMSP (Defense <br /> <br />Meteorological Satel1ite Program) satel1ite images were <br />inconclusive due to the presence of natural cloudiness, too. <br /> <br />6.5 COSTS <br />The estimated cost of air cloud trail production opera- <br />tion, assuming one hour of climb and one hour of descent <br />with continual cloud trail production for two hours in- <br />between, is on the order of $2/km. This estimate is based <br />on our 1978 operations, and includes only aircraft costs, <br />