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<br />produced ice crystals blew over the crest before falling. <br />A similar situation occurred at McGuireville. Simulated aerial <br />seeding with dry ice along Victor Airway 105-257 produced <br />good increases from the Verde River to the Mogollon Rim. <br />Replacing dry ice with silver iodide displaced the area of <br />effects further downwind, in this case beyond the crest. <br /> <br />The seeding agent for ground-based seeding that is shown <br />in Table 3.1 was silver iodide-ammonium iodide with the addition <br />of ammonium perchlorate (see Section 3.1.2). Several simulations <br />were done without the ammonium perchlorate additive. All <br />suffered in comparison to those shown in the table. Although <br />no formal field evaluations of the ammonium perchlorate additive <br />have been performed, these modeling results suggest that it <br />could be beneficially used in Arizona. <br /> <br />3.2.2 Modeling Results for the Lower Salt River {SALTRVRl <br />As was mentioned earlier, the maximum terrain elevation of <br />the Mogollon Rim for the SALTRVR cross-section is less than <br />2200 m. As a result, under stable flow, a seeding plume being <br />lifted over the Mogollon Rim generally would not be mixed <br />high enough to activate ice nuclei. Model simulations of <br />ground-based seed~ng at Superior, Miami, and Cibecue under <br />stable conditions all resulted in no seeding-related increases <br />in precipitation (see Table 3.2). If the air mass is colder <br />(i.e., -5oC level at 1500 m), better results should occur. <br />However, an air mass that cold is unusual in Arizona, especially <br />when associated with southwesterly flow. <br /> <br />Under more convective conditions, model simulations of <br />ground-based seeding produced good increases. Seeding locations <br />included Superior, Miami, and Cibecue. An important consideration <br />here is that the precipitation below the Mogollon rim would <br /> <br />3-19 <br />