A dispersion model is essentially a computational procedure for predicting
pollutant concentrations downwind of a source. Current models are based on knowledge
of the emission characteristics (stack exit velocity, plume temperature, stack diameter,
etc.), terrain (surface roughness, local topography, nearby buildings), and state of the
atmosphere (wind speed, stability, mixing height, etc.). The main purpose of this
chapter is to provide an overview of different dispersion models. The objective of
dispersion Modeling is to predict the rate of spread of the pollutant cloud, and the
consequent decrease in mean concentration. The model must be able to predict diffusion
rates based on measurable meteorological variables such as wind speed, atmospheric
turbulence, and thermodynamic effects. Therefore, algorithms at the heart of air
pollution models are based on mathematical equations describing these various
phenomena, which, can be used to predict concentration distributions downwind of a
source when combined with empirical (field) data.
Keywords: AERMOD, AERSCREEN, atmospheric downwash, atmospheric
turbulence, Box Model, CALPUFF, coastal-area meteorology, Dense Gas Models,
dispersion models, emission, Gaussian Models, Lagrangian Models, land/sea
breeze, Mesoscale models, MM5, New-generation Models, OCD, plume
fumigation, pollutant concentration, Screening Models.
