Keywords: atmospheric dispersion, Lagrangian stochastic model, nocturnal stable conditions, urban boundary layer
Simulations of atmospheric dispersion in an urban stable boundary layer
The results of numerical simulations of tracer dispersion in an urban stable boundary layer are presented. Both Gaussian approximation and fourth order closure are considered and a Gram-Charlier probability density function is used in our Lagrangian stochastic model. Different parameterisations for the boundary-layer height and different values of kurtosis are tested. The model is based on the generalised Langevin equation, whose coefficients are solution of the Fokker-Planck equation and plume rise is taken into account. The model accuracy is assessed by means of a model evaluation based on the predicted and observed crosswind integrated concentrations, maximum on the arc and standard deviation of the crosswind concentration distribution on the arc.