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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Three types of seeding techniques are being considered for <br />aircraft seeding. Droppable silver iodide flares of various burn <br />rates could be utilized for the types of cloud systems anticipated <br />over Colorado's mountains or a silver iodide solution burning <br />generator could be utilized 'when these seedable cloud systems are <br />present. The flares would be dispensed at rates to meet the <br />seedability rate calculated for each specific cloud system and <br />the speed of the aircraft. The use of dry ice could also be <br />considered for aircraft seeding. One potential problem with dry <br />ice seeding is finding a seeding signature in the precipitation <br />observed at the surface to verify that dry ice participated in <br />the cloud precipitation process. <br />The seeding solution proposed for this program would be an <br />acetone solution of silver iodide and ammonium iodide. Because <br />of the normally cold temperatures observed in Colorado's cloud <br />systems, an acetone solution of silver iodide and sodium iodide <br />could be utilized. with the production cost of both solutions <br />being comparable, the higher nucleation efficiency of the <br />ammonium iodide solution over the sodium iodide solution at cloud <br />temperatures in the range of -70C to -120C makes it preferable. <br />One potential drawback to the ammonium iodide solution is the <br />useful shelf life which is around five to six months. This would <br />require a solution supplier to respond to requests for additional <br />solution within three to four weeks in order to assure continuity <br />of the program operations each season without the program having <br />an excessive supply of solution remaining at the end of each <br />season. <br />A new solution of silver iodide in a methyltriethanol-ammonium <br />iodide solution of acetone has been tested as a seeding agent by <br />csu. Initial tests indicate that this solution is as efficient as <br />the ammonium iodide solution as a nucleant and appears to have a <br />shelf life of several years.ll Prior to the proposed starting <br />of this program, further investigations would be made into newer <br />and potentially more efficient seeding agents. It is recommended <br />that whatever solution is finally selected for use by this program, <br />it should be thoroughly tested in field equipment under operational <br /> <br />-29- <br />