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<br />e. Use high altitude generators on barriers just upwind of the intended target barriers, such as the <br />San Pitch Mountains in the case of the Wasatch Plateau. This approach would provide important <br />additional time for seeded ice particles to grow and fall to the surface. <br /> <br />. <br />. <br /> <br />f. Consider whether aircraft seeding can provide AgI aerosol to sufficiently cold SL W regions <br />during relatively warm stonn periods. However, aircraft seeding with AgI generators may often <br />be impractical when the SL W is contained in a shallow, mildly supercooled layer just above the <br />mountain barrier. That is, aircraft with attached AgI generators may not be able to safely operate <br />at sufficiently low altitudes during many storm episodes. Dropping of AgI flares is an alternative <br />which may be cost prohibitive when duration and volume of coverage are considered. <br /> <br />7.4.2 Additional Recommendations <br /> <br />In addition, it is recommended that automated liquid propane seeding be expanded from the three <br />dispenser operation already in use east of Ephraim, Utah. This approach would profit from the use of <br />direct current icing meters which could be operated in the field with solar panels and storage batteries. <br />Available commercial models employ an alternating current heater requiring field use of an inverter. <br />However, according to personal communication with one of their representatives, circuit changes could be, <br />made by the manufacturer. This approach should be affordable and has the several advantages previously <br />discussed. Unlike automated AgI generators, propane dispensers are simple, reliable, and economical <br />devices. <br /> <br />As a separate recommendation, numerical modeling studies should be used to determine optimum seeding <br />locations and source strengths of both AgI generators and liquid propane dispensers. The Clark model has <br />been shown to produce reasonable simulations of SL W cloud and AgI aerosol transport. The model is set <br />up on a workstation and simulations can be produced at limit cost. The model should be run with various <br />seeding configurations and under the range of storm conditions found in Utah. Anabundance of sounding <br />observations already exists for model initiation. Such modeling investigations should lead to improved <br />AgI generator and propane dispenser placement. Reasonable estimates could be made of the AgI ice <br />nuclei production and propane ice crystal production needed to affect the range of SL W cloud <br />temperatures typically found over Utah's mountains. <br /> <br />'" :~ <br /> <br />Finally, it is strongly recommended that any future evaluations ofthe Utah operational program, whether <br />statistically or physically based, be conducted by totally disinterested parties. This would add objectivity <br />and credibility to the evaluations. In fact, it is recommended that any meteorologists or statisticians tasked <br />with such evaluations should have had no prior involvement in the Utah operational or experimental <br />programs, or any financial stake in the operational program. Anyone with prior involvement likely <br />already has firm opinions about the operational program's effectiveness. These opinions might inject bias <br />into future evaluations as might any financial interest. <br /> <br />33 <br />