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Show for large distances downwind. The terrain in his work is des c ribed as " ge ntly rolling" so the same principles might not apply to the mountainous t e rrain in the Park Range. However, Walton Creek canyon is well aligned with Emerald and Rabbit Ears Pass. It is therefore proposed that during periods in which Emerald was above any inversion , some of the silver iodide particles were channeled up the canyon to the observing site. This is not to imply that there was no vertical mixing. A number of aircraft flights have been mad e in the area with the results showing vertical mixing of the particles to at least 2300 feet above the release site in the first 4. 5 miles of travel. An examination of the data shows a relationship exists between the ice nucleus concentration as measured at Rabbit Ears Pass and the wind velocity measured at Emerald Mountain. Four cases have been delineated: The one cycle per hour pulses of Agl seeding could be recognized in the nuclei data with a transport time determined by the Emerald wind (Figure 73). (1) (2) A similar wind field existed as in Case #1, but the nuclei concentration remained near background (Figure 7 4). (3) No increase in nuclei concentration was observed due to an inversion whose top was above the elevation of Emerald Mountain and below the observing site (Figure 75). (4) The nuclei concentration remained high for greater than an hour after the inversion broke (Figure 76). The obvious case of low nuclei count when all the winds are in the wrong direction is not included. In these instances another nuclei counter, located at Buffalo Pass (elevation 10, 250 ft. MSL), was sometimes useful. 4. 2 Snow Crystal Replica Collections Many hundreds of plastic-coated glass slides were exposed for collection of snow crystal replicas during operational periods. 9ne phenomenon which was frequently noted in all four years of seeding was an increase in the frequency of occurrence of hexagonal plates during predicted seeding effect periods. Many of these hexagonal plates were quite small (::; 200 µ and frequently < 100 µ). An example of this type of plate is shown in Figure 77. Small hexagonal plates with inner stellar structures have been found to be associated with Agl seeding in the Yellowstone experiments (Schaefer, 1967). Another phenomenon observed during several expected seeding effect periods was the impaction of tens to hundreds of tiny hexagonal plates (30 µ to 80 µ diameter) on larger plates and dendrites (Figure 78). A tentative explanation for this phenomenon is the interception of a low altitude concentration of small hexagonal plates (grown 127 |
