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heated wind sensors, it is recommended that a primary prototype testing site be located (via permission and/or cooperative agreement) at the Desert Research Institute's (University of Nevada at Reno) Storm Peak Laboratory, that is equipped with electrical power and is accessible via Steamboat ski lifts and snowmobiles. The laboratory has shelters for instruments and data collection by technicians. A second prototype site can be instrumented at a somewhat lesser level but must also be accessible by 4-wheel drive and/or oversnow vehicle. Currently, the Storm Peak Laboratory is manned periodically to collect cloud and aerosol data. Observations by aircraft mounted instrumentation are not recommended as a necessary data collection component because aircraft can rarely operate low enough in orographic clouds to provide desired observations. However, any agency willing to supply an instrumented aircraft and personnel to collect data will be encouraged to do so. Because natural snow showers will often mask seeding effects, randomization should be used on at least some test seeding trials of the design phase. The randomization scheme should be determined after some modeling studies are conducted and the terrain is better known. Should the two-year field testing have normal or above seeding opportunities, there may be an opportunity to collect adequate treatment and control samples for a seeding effect assessment on precipitation. Generally, contamination of the control will not be a significant problem with the propane seeding approach because topography will largely control the transport of seeded ice crystal plumes. Only a brief residual seeding effect will occur downwind from the propane dispensers as seeded crystals are transported out of the target area. Propane seeding will not have the long-distance ice nucleation "contamination" that may occur with AgI releases. However, it may be found that certain zones of the Headwaters Region are best suited for AgI seeding. The seeding design should not eliminate this possibility. An appropriate "buffer zone" of at least 3 miles wide should separate the two prototype study zones. The number of seeding devices per prototype site should be determined after some modeling studies and terrain inspection have take place. The areas downwind from each seeding equipment line should have similar instrumentation. Experimental units should be on the order of 1-3 hours in duration to help minimize natural temporal variations. Specified delays between experiments allow for flushing of seeded crystals from the area. The test seeding trials should work toward automation thus requiring little or no human intervention. In this mode of operation, many test trials can be accumulated over a winter, in simulation ofthe operational phase of the program. A tracer gas should be used in the test trials to document the passage of propane-seeded air parcels. Ice particle concentrations (IPC) and associated snowfall rates should react to seeding. Some seeding trials will display an obvious effect in the targeted area while others will be impacted by high natural temporal and spatial variations in IPC and snowfall rate, which necessitates statistical testing. Contamination may occur from highly variable winds. Scanning by microwave radiometer (possibly also by scanning radar) of the SL W distributions approaching the target and control areas should be used in detecting natural changes that will contaminate test events. 3.7. Cloud Seeding Operations Cloud seeding trials will be conducted as part of the design phase. Automated conduct of seeding needs to be developed. This involves the development of computer software that includes the following components. ~ Logic to initiate or terminate cloud seeding by individual seeding devices based on checking established criteria built into the software ~ Logic to interrogate field equipment on the status of local weather measurements and the 13