The Study of the Diffusion of Gases Or Aerosols in the Lower Atmosphere
Final Report Under Contract No. AF 19(604)-1058
Description:... The principal objectives of the research described in this report have been to achieve improved understanding of the basic physical processes involved in the dispersal of airborne material in the lower atmosphere; and, to establish empirical relationships between basic diffusion parameters and direct meteorological indicators that permit satisfactory quantitative estimates of dispersal from continuous point sources, over travel distances of the order of 1 km, in a wide variety of general weather conditions. These objectives have been achieved largely as the result of a series of comprehensive field observations involving simultaneous measurements both of diffusion and the structure of atmospheric turbulence. The diffusion measurements comprise 10-min average concentrations of sulfur-dioxide gas emitted from a continuous point source near ground level, at travel distances from 50 to 800 m from the release-point for the tracer. The meteorological observations include mean wind speeds, frequency distributions of azimuth oLnd direction, vertical profiles of wind speed and air temperature, and measurements of the fluctuations in wind velocity obtained from bivanes and heatedthermocouple anemometers. Over one hundred individual experiments of this type were carried out at Round Hill and at a field site near O'Neill, Nebraska during Project Prairie Grass, an extensive series of diffusion measurements sponsored by the Air Force Cambridge Research Center during the summer of 1956. These data comprise the most comprehensive set of small-scale diffusion and meteorological observations currently available. They provide a fairly complete picture of the probable variations in basic diffusion parameters over travel distances of the order of 1 km in all conditions of thermal stratification ...
Show description