A STUDY OF THE TRAJECTORIES AND DIFFUSION PATTERNS OF GROUND-GENERATED AIRBORNE PARTICULATES UNDER OROGRAPHIC WIND-FLOW CONDITIONS

Abstract

In late June and early July, 1956, a series of experiments was performed to determine the wind structure over an orographic barrier and to ascertain whether ground-generated aerosols reach cloud heights in such a situation. Zinc-sulfide particles were dispersed in an oil fog from a ground-located fog generator and collections were made using airborne impactors. Particles were found at elevations of at least 14,000 ft at distances out to at least 20 mi. However, ?plumes? were found to be considerably broader than had been anticipated, and the structure of the wind over a mountain ridge is judged to be substantially more complex than has been assumed in cloud-seeding operations.