Air Quality Dispersion Modelling in Urban Areas

Dr Helen Dacre

Many dispersion hazards and high air pollution episodes occur in urban areas. Thus it is important to accurately represent the processes occurring within the urban boundary layer in air quality dispersion models. Urban areas can modify dispersion in the boundary layer compared to a rural area in several ways: firstly, increased heating at the urban surface can increase the depth of the boundary layer. Secondly, increased turbulent mixing due to the enhanced friction of the rough surface can rapidly disperse any pollutants released at the surface. Finally, storage of heat within the urban fabric is released slowly after sunset and can prolong turbulence even after sunset. Current dispersion model parameterisations of the urban boundary layer often do not include these processes and thus can lead to errors in predicted concentration fields. This project involves a comparison of observed urban boundary layer dynamics and air quality measurements with parameterisations in the NAME dispersion model.