Numerical study of atmospheric dispersion under unstably stratified atmosphere

Abstract

Pollutant dispersion under unstably stratified atmosphere was investigated numerically using a second-order closure turbulent dispersion model. The effect of atmospheric stability, which affects the plume trajectory, was studied by carrying out two-dimensional calculations in the horizontal and vertical planes. It was found that the present numerical model can predict several non-Gaussian features of plume behaviour under unstably stratified atmosphere, such as the descent and the rise of a plume, both of which cannot be predicted by k-theory dispersion and conventional Gaussian models. The calculations agreed well with recent findings from experimental studies and another numerical model. Based on the above observations, the second-order closure dispersion model was found to be a promising technique for studying the plume behaviour under different atmospheric stabilities.