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<br />. <br /> <br />In 1986 a new formulation was used in the 2% silver iodide liquid <br />solution. This amounted to adding certain quantities of sodium <br />perchlorate and ammonium perchlorate to the existing liquid solution <br />previously in use. What this does is produce a hygroscopic <br />particle---one which attracts Moisture and upon which water droplets <br />will form--- thereby trapping silver iodide nuclei within the dropl8ts <br />as they ascend from its base through the cloud. Also} the particles <br />not trapped in water droplets from hygroscopic action will continue <br />acting as "contact') nuclei which physically impact with water droplets <br />to eventually create ice crystallization---the sole process employed <br />before the perchlorates were added to the solution. The result is <br />that great numbers of ice crystals are formed at relatively warm <br />temperatures within a cloud, more so than when using the old <br />formulation. At this point results on the W~(WM program using the new <br />formulation is subjective at best, however, it is the opinion of this <br />W)~ i t..(?r t.ha t. we have E.'>::p12r i enc ed e::<c I? 11 ent. l~\?SU 1 i:..s \\' i t.h it. both \,k,lhen <br />using it in rainfall augmentation and in reducing hail. For an <br />isolated case study on rainfall augmentation please see the Section <br />VIrI: Case Study - August 24, 1986. <br /> <br />. <br /> <br />On the WKWM program the seeding agent1 dry ice, is dispensed <br />ttlrough an opening in the floor of an aircraft capabl,e of flying well <br />into the supercooled region of the clouds. The dry ice dispenser has <br />been designed to autonlatically release the commercially mallufactured <br />dry ice pellets at the rate of one pound per mile of flight. Dry ice <br />dropped into the supercooled part of a cloud immediately converts <br />water droplets into ice crystals. Dry ice is more effective thaTl <br />silver iodide in producing i(:e cl~ystals lower in the superco'~led <br />portion of the cloud---approaching freezing; silvel~ iodide only starts <br />producing substantial numbers of ice rluclei around -SC (22F). .In <br />terms of cost effectiveness dry ice produces the greatest numbers of <br />ice nuclei for the money when compared to silvel~ iodide. <br /> <br />In order to seed clouds to obtain the desired result, <br />irrespective of the seeding agent lJsed and the method of seeding, each <br />cloud must be treated at ttle proper' time. In so doing} through the <br />cold cloud process, it is possible to produce the optimum ice crystal <br />concentrations in naturally deficient clouds so as to either increase <br />precipitation or to reduce hailstone sizes. <br /> <br />Of further significance may be what is known as the dynamic <br />effeEt due to seeding. When flatural environmental conditions are <br />satisfactory, cumulus clouds may be stimulated to grow larger and <br />persist longer than would be the case if left unseeded. This is done <br />by getting the seeding agent il,to the supercooled part of the cloud to <br />promote droplets becoming ice crystals. When this water-to-ice <br />conversion pl~ocess occurs rapidly witflin the cloud, latent heat of <br />fusion is released on suel, a scale that the cloud is made slightly <br />warmer and, therefore, more buoyallt. As the cloud grows, it must draw <br />in much more water vapor from levels below its base and, therefore, <br />puts more moisture into the precipitation-making process. This allows <br />the cloud to "pl.ocess" more water over a longer period of time and to <br />do so more efficiently than if not seeded. <br /> <br />The cloud systems in SQlAthwest Kansas that are responsible for <br /> <br />7 <br />