A review of dispersion modelling and particle trajectories in atmospheric flows

Atmospheric and turbulence modelling, boundary layer parameterization, and current dispersion modelling techniques are reviewed. Dispersion models for atmospheric flow conditions include the K-Diffusion model, Gaussian Plume model, and Lagrangian particle tracking techniques (Gaussian Puff model), and their applications in CALPUFF (a commercial software package) are described. Studies of Gaussian Plume and Puff models in stable, neutrally stable, and unstable boundary layers show that the puff method reproduces acceptable plume model results in simple flow cases. The influence drag and gravity forces have on the motion of pollutant particles are investigated by means of derivation and analysis of the equations of translational motion. Incorporation of the drag and gravity forces into the Gaussian Puff dispersion model shows that the effect these forces have on the growth of a pollutant plume depends on the magnitude and frequency of the turbulent flow-field fluctuations. The Gaussian Puff model is flexible in that it can be applied in complex flow conditions; however, the assumption of the Gaussian distribution of pollutants does not account for particle deposition.