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Show cipitation, while the Rabbit Ears record is less clear. 4. 5. 3. 1. 6 Replica Series and Evidence of Agl Nucleation A series of eighty replica slides were exposed at Rabbit Ears during this operation. These slides were analyzed for crystal type and size and also treated by the new technique for identification of Agl nucleation. Figure 119 shows the. percentage of various crystal types and sizes for each slide (irregulars consisting of rimed stellar fragments and other unidentifiable clutter were not counted). There was a marked increase in hexagonal plates during the first seeding effect period. A series of photographs of individual crystals for various times is shown in Figures 120a through 120g. These show (1) a predominance of large dendrites without microscopically visible nuclei at their centers prior to arrival of the seeding effect, (2) the presence of some dendrites with Agl centers during seeding effect, (3) a marked increase in very small hexagonal plates during the seeding effect, and (4) many very small hexagonal plates scavenged by dendrites or larger plates during the seeding effect (as opposed to rime droplets scavenged prior to seeding effect). The percentage of individual crystal replicas growing Agl centers on each // replica slide (Figure 121) gives strong evidence of ice crystal nucleation by !! ,1 Agl particles during the two periods of seeding effect. Figures 119 and 121 ,l in combination indicate that hexagonal plates were the most frequently observed type of crystal possessing AgI centers. II During the second seeding effect period riming rates were the lowest observed for the entire day of operations. 4. 5. 3. 1. 7 Summary and Conclusions From the data studied it is concluded that (1) Ag! particles acted as ice nuclei during both periods of seeding effect, (2) most of the crystals initiated by AgI partic'tes were small hexagonal plates, but with a few seeded dendrites evident, (3) some of the very small hexagonal seeded plates were scavenged by larger plates and dendrites, and (4) a positive seeding effect was evident in the precipitation rates, at least during the first seeding period, in good time and space agreement with seeded precipitation trajectory calculations, 4. 5. 3. 2 Case Study of Operation on 2 January 1969 An inversion existed between the elevation of Mt. Harris and the ridge durin~ this seeding event, and it was selected as a case in which no seeding effect should be expected. 194 d l: II ;1 !:1! 1: |
