Measurements of the Movement, Concentration and Dimensions of Clouds Resulting from Instantaneous Point Sources

Abstract

Puffs of the inert gas 85Kr were released at the surface level and were permitted to drift through a three-dimensional grid of Geiger counter sensors extending to a height of 21 m and to a distance of 800 M. Concentrations were recorded as a series of 4.8-sec duration mean concentrations for each of the 64 sensors. Data specifying the effective speed, the effective height, the magnitude of short-period concentrations, the magnitude of crosswind and downwind concentration integrations, and the dimensions of puffs are reported. It was found that: 1) the speed with which a puff reached a 1.5 m elevation field sensor increased with distance from the source (or with travel time); 2) at the 1.5 m elevation, peak values of short-period concentration, exposure, and crosswind integrated concentration increased with increasing atmospheric stability; 3) regardless of the atmospheric stability, puff dimensions along a downwind axis exceeded those along a crosswind axis, and the crosswind dimension exceeded the vertical; 4) for a given distance, the ratio of cross-wind to downwind dimensions decreased as atmospheric stability increased; 5) the ratio of crosswind to downwind puff dimensions increased with distance (or time) in an unstable atmosphere but decreased slightly in stable atmospheres, 6) the ratio of vertical to downwind puff dimensions decreased with distance (or time) regardless of stability; and 7) the effects of stability on puff dimensions were best shown when dimensions were considered as a function of time rather than distance from the source.