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<br />002573 <br /> <br />CONTRACTOR: Colorado International Corporation, Boulder, Colorado <br />CONTRACT NO. 6-07-DR-20100 <br />PRINCIPAL INVESTIGATOR: R. T. Beaumont <br />PERIOD: May 18, 1976, to November 30, 1976 <br />FUNDING: FY76 - $22,339 <br />T .Q. - $22,340 <br /> <br />As part of the 1976 HIPLEX field season, the contractor provided <br />research personnel and a cloud survey/seeder aircraft at Miles City, <br />Montana. Seeding systems included silver iodide/ammonium iodide/ <br />acetone generators, and wing- and fuselage-mounted racks for ejectable <br />and burn-in-place silver iodide pyrotechnic flares. Pellet-size dry <br />ice was also released from the aircraft. Variable concentrations and <br />delivery methods were tested to evaluate seeding materials and <br />dispersion techniques. An onboard data system measured and recorded <br />data on natural and seeded clouds including temperature, dewpoint, <br />liquid water content, and updraft profiles. Time-lapse photographs <br />of natural and seeded clouds were taken. These data have been used <br />in developing the High Plains cloud climatology. <br /> <br />CONTRACTOR: University of Washington, Seattle, Washington <br />CONTRACT NO. 6-07-DR-20110 <br />PRINCIPAL INVESTIGATORS: Peter V. Hobbs and Lawrence F. Radke <br />PERIOD: July 1,1976, to November 30, 1978 <br />FUNDING: FY76 - $35,000 <br />1.Q. - $78,000 <br />FY77 - $88,751 <br />FY78 - $48,515 <br /> <br />The contractor provided research personnel and an instrumented <br />aircraft to study atmospheric aerosols, cloud structures, precipitation- <br />producing mechanisms, and the potential for modification by various <br />types of seeding in the Miles City HIPLEX area. Small cumulus clouds <br />and cumulus complexes were found to contain high particle concentra- <br />tions and to have narrow particle size spectra; broader spectra and <br />lower particle concentrations were measured in embedded cumulus. <br />Growth of precipitable particles is dominated by ice-phase processes. <br />Measurements indicate that, in this area of the High Plains, seeding <br />small cumulus clouds and embedded cumulus from cloud top with dry ice <br />or silver iodide pyrotechnics to produce ice particle concentrations <br />of 1 to 10/L may increase precipitation. However, it seems less <br />likely that precipitation from cumulus complexes could be increased <br />by seedi ng at the same rates. <br /> <br />111-26 <br />