Boundary-layer pollutant concentrations over complex terrain

Given the incident profiles of wind velocity and pollutant concentration, we seek to determine the 3-dimensional concentration field of a pollutant upon a region with complex terrain. The analytic solution of the wind velocity in a 3-dimensional boundary-layer model by Walmsley et al. (1980) is utilized as a forcing function in the simplified concentration perturbation equation for a pollutant. The resulting solution applies to an isolated cosine-squared hill in a neutrally stratified boundary-layer flow with a surface type which absorbs the pollutant totally. The solution shows that the concentration perturbation field is organized in accordance with the wind field. In particular, the east-west cross-section is 180° out of phase with the velocity perturbation field. The vertical profiles of the concentration perturbations for selected grid points approach the value of the upper boundary condition very rapidly.