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Since the AgI plumes resulting from either ground or orbiting aircraft releases will be monitored by aircraft, the gauges likely affected by the seeding can be estimated for each experiment. Precipitation amounts from these "target" gauges will be compared with nearby "control" gauges expected to receive only natural snowfall The cloud physics aircraft will also monitor the positions of aircraft-released lines of AgI and associated ice particles. The passage of these across-the-wind seedlines should be evident in the time histories of precipitation across the gauge network when seeding produces detectable snowfall. 1.5.8 Additional Ground Systems. - An additional monitoring station will be operated to obtain manually very high-resolution precipitation measurements, snow accumulations for silver analysis and microphotographs, similar to the Allen Lak(: manual observations. These data will be collected for each experiment at one of two protected clearings in the forest. During seeding experiments that release an along-the-wind plume of AgI (secs. 1.6 and 1.7), a site about 20 km south of Allen Lake will provide crosswind, nonseeded control observations. During aircraft releases of crosswind seedlines of AgI, monitoring will take place about 5 km north of Allen Lake to provide a second set of high-resolution measurements in the area expected to be affected by seeding. Both clearings will have a small refrigerated shelter to facilitate snow sampling when surface temperatures are near 0 0 c. An automated weather station will be maintained near Ilhe Crooks Trail Road seeding generator locations to provide near-surface observations of windspeed, wind direction, and temperature, These data and derived statistics may be transmitted to the project operations center to assist in real-time decisions concerning missions, The measurements also will be used for post hoc analysis of the physical seeding experiments. Two rawinsonde sites will be operated during experiments, one at Allen Lake and the other near Camp Verde about 45 km southwest of Allen Lake (in addition, the NWS takes soundings at 0500 and 1700 m.s.t. each day at Winslow, 70 km east-northeast of Allen Lake). Releases will be made at about 2-hour intervals, starting when the decision is made to commence an experiment, and continuing until completion of the mission. These soundings of wind, temperature, moisture, and pressure will be used as input for a targeting model to predict where to release AgI so as to affect the target. The upper air observations also will be valuable in post hoc analysis of each experiment. The Camp Verde rawinsonde site will be equipped with a video camera to take time-lapse photos of the cloud cover over the general target area during daylight periods. These will be useful in post hoc analysis of cloud type, evolution, and structure. / It would be highly desirable to operate a second radiometer several kilometers southwest of the crestline, or in a mobile mode along Stoneman Lake Road, to improve information on the upwind extent of the SLW. Delineation of the SLW zone's posiltion upwind and over the Mogollon Rim is very important in evaluation of seeding potential. Ice crystal growth is very dependent upon the amount of SLW present and its extent along the crysta~ trajectories. Numerical models used to calculate ice particle growth and fallout must estimate where the SL W exists and in what amounts, but these estimates need confirmation by actual observations. At present, knowledge concerning SLW fields over mountain barriers is limited because of the difficulties of observation. A second radiometer could significantly assist in improving this knowledge of SL W over the experimental area. It could make RHI (range-height indicator) scans in the vertical plane along the wind. Such scans would provide observations directly overhead and also along slant angles upwind and downwind of the radiometer. Radiometer data can be difficult to interpret since no 17