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Show rate set irito the range. As the range gate servoed out, a recording was made of the AGC voltage and slant range. nate iden (3) When the range had reached a pre-determined value, the range sarn sive was slewed to zero, the antenna elevation angle decreased and a new scan started. This procedure was repeated until the antenna elevation angle was con: just large enough to miss ground targets. EG& The values for range, elevation angle and AGC voltage were then coded on punch ca.rds for computer analysis. The computer prepa~ed a graph of the resultant data in which the abscissa is height and the ordinate horizontal range. At various points within this graph were plotted values of Z or I obtained from the AGC scans. An isopleth sketch was then made encircling points of high intensity. Using this method it is possible to readily look for an increase or decrease in signal intensity which might be related to seeding. 2. 6 Snow Crystal Replica Collection and Analysis duri on f in ii Usi1 Pro soh tak( aftE mic Ex, Many hundreds of plastic-coated glass slides were exposed for the collectio sho of snow crystal replicas during operational periods in the Park Range. Mo vis of the slides were exposed at Rabbit Ears Pass, although special series we occasionally taken at other locations in the experiment area, notably at 2. Buffalo Pass in the 1966-67 season and at Valley View, Steamboat Springs, Emerald Mountain, and occasionally at Mt. Harris during 1965-66. An Sm The snow crystal replicas were collected by exposing 3¼ x 4 inch glass slides coated with 1 % formvar in ethylene dichloride solution. Exposure time varied from about 30 seconds to three minutes depending on snowfall rate. The water content of the crystals was then allowed to sublimate away while the slide dried at subfreezing temperatures for 12 hours. Sampling frequency ranged from 5 minutes to 30 minutes with most series collected at 5, 10, or 15 minute intervals. 2. 7 Identification of Silver Iodide Particles as Ice Nuclei Knowledge of the geographical distribution of silver-in-precipitation concen· tration is helpful in studying the effects of cloud seeding using silver iodide, However, silver iodide can occur in precipitation samples due to (1) AgI particles acting as ice nuclei, (2) scavenging of AgI particles by precipitatio and (3) sedimentation of AgI particles. Therefore, in order to determine whether or not (and to what degree) AgI particles participate as ice nuclei in the precipitation process, it is necessary to identify individual AgI particles in relation to individual ic.e crystals. In the 1967-68 operational season, an electron microscope technique origi- 22 de1 in fr( se ln p: a tc di ai ti p, |