||Atmospheric Stability Class Determinations on a 481-Meter Tower in Oklahoma.
DeMarrais, Gerard A. ;
||Environmental Sciences Research Lab., Research Triangle Park, NC.
Air pollution control ;
Wind direction ;
Atmospheric dispersion ;
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The tall stack is often presented as a means for reducing ground-level concentrations of a pollutant. A recent comprehensive review (Hales, 1976) of the literature referenced many reports on ground level measurements of pollutants emitted from tall stacks but showed that very little information was available on the meteorological conditions associated with the dispersion aloft. Statistics on these phenomena for levels above 100m are presented and the probable meaning of these results with regard to dispersion are discussed. Data from seven heights on a 481-meter tower in Oklahoma are analyzed to show the variation of stability with height and time. Wind direction fluctuations at the various heights are analyzed to determine the stability class associated with horizontal dispersion and the temperature difference between pairs of heights are analyzed to determine the class associated with vertical dispersion. The Oklahoma results are compared to previously reported results obtained on a 367-meter tower in South Carolina. The results from the two widely separated sites corroborate one another. The two classifying techniques at both sites show that there is a marked increase in stability a little above 100 meters. This result indicates that dispersion estimates for effluents from stacks taller than 100 meters could readily be in error when based on observations below 100 meters; the observations at the lower heights would indicate more rapid dispersion than would be indicated at effluent height.