On plume dispersion over two-dimensional urban-like idealized roughness elements with height variation

A series of large-eddy simulation (LES) models over two-dimensional (2D) urban-like idealized roughness elements with height variation were performed. Results show that building-height variability (BHV) could enhance the aerodynamic resistance of the urban surfaces. Both the air exchange rate (ACH) and the vertical dispersion coefficient ðz increase with increasing the friction factor, implying that the air quality in both street canyons and urban boundary layer (UBL) could be improved by increasing the surface roughness via BHV. In addition, the parameters used in the estimates of dispersion coefficient are modified substantially by the friction factor, suggesting that friction factor could be used to parameterize dispersion coefficient of urban Gaussian plume model.postprin