Study of atmospheric dispersion under low wind speed conditions

摘要

This paper presents the analysis of atmospheric SF_6 tracing experiments carried out under low wind speed conditions associated with strong thermal stability on a flat terrain. Analysis of meteorological data, processed in the form of probability densities, reveals that unsteady character of the current increase the greater the stability. The spectral densities of the three wind components deduced from sonic anemometers show that the horizontal current is dominated by large-scale turbulent structures, and that there is a weakening of energy levels in the neighborhood of 0,01 Hz. Tracings confirm that the levels of ATC (Atmospheric Transfer Coefficient) are greater the stronger the stability. Release impact is as closely linked to the increase in pollutant residence time as to higher instantaneous concentration levels. Lastly, ATCs deduced from a gaussian model being developed at IPSN gives good agreements with the experimental values.