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<br />II <br /> <br />II <br /> <br />direction of plume travel, although the presence of Fish Creek Canyon, <br />running in line with the generating site and observing site, must exert <br />some control. When Emerald was under an inversion, the nuclei con- <br /> <br />II <br /> <br />centrations were above the normally expected background. <br /> <br />II <br /> <br />In April 1967, the ice nuclei counte l' was moved from Buffalo; <br /> <br /> <br />Pass to an observing site on top of Thunderhead Mountain -- to get an <br /> <br /> <br />idea of the nuclei concentrations at this "closer in" site. Because <br /> <br />II <br /> <br />Thunderhead is not at the head of a canyon, and is much closer to Emerald <br />(5 miles), the plume of AgI was much better defined, Figure 17. Exam- <br />ination of counter data shows that the plume reaches Thunderhead when <br />the Emerald wind is :1:200 of the Emerald-Thunderhead azimuth. It is <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />significant that changes of nuclei concentration due to wind velocity <br /> <br />variations on a time scale of 10 minutes were detectable, <br /> <br />I <br /> <br />The primary reason for measuring ice nuclei concentrations is <br /> <br /> <br />to obtain a model for the transport time of these nuclei from the seeding <br /> <br /> <br />site to the location of snow measuring instruments, From available <br /> <br /> <br />data, the following model has been constructed for nuclei flow to Rabbit <br /> <br /> <br />Ears: <br /> <br />I <br /> <br />I <br /> <br />o <br /> <br />nuclei concentrations at Rabbit Ears will exhibit a pulsed <br />characteristic two thirds of the time when the Emerald <br />wind direction is between 270 and 3500 and the Emerald <br /> <br />I <br /> <br />I <br /> <br />wind speed is greater than about 10 mph. If the Emerald <br />wind is slower than this, the transport time is better given <br />by the Mt. Harris 11,000 ft. winds, If the difference be- <br />tween the wind speeds at Mt. Harris and Emerald is between <br />30 and 40 mph, the transport time is determined by the <br />average wind speed. All this assumes no inversion and fair- <br />ly good alignment between the Emerald and the upper winds. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />- 38 - <br /> <br />I <br />I <br />