High-resolution and accurate air quality concentration data are needed for detailed exposure and health effects calculations. Simulating such data numerically requires realistic treatment of both local emissions and background concentrations transported from further afield. This study combines regional and urban scale modelling and uses adjusted emission factors for NO<sub><i>x</i></sub> and NO<sub>2</sub> and non-exhaust emission rates of PM<sub>10</sub> and PM<sub>2.5</sub> to reflect real-world emissions more accurately. Three modelling approaches have been used to simulate air quality in 2012 across London: a regional chemistry-climate model with 5&thinsp;km horizontal resolution and gridded emissions; a local dispersion and chemistry model with explicit road source emissions; and a coupled regional-to-local modelling system combining the two individual models. The performance of each of the models is assessed against measurements from background and near-road sites in London in terms of annual averages, high hourly average concentrations and diurnal cycles. The regional model shows good agreement compared to measurements for background sites for these metrics but under-predicts concentrations of all pollutants except O<sub>3</sub> at near-road sites due to the low resolution of input emissions and calculations. The urban model, using measured concentrations as regional background, and the coupled model show similarly good agreement for most pollutants at both background and near-road sites. Using the coupled model, it is estimated that 13&thinsp;% of the area of London exceeded the EU limit value of 40&thinsp;µg&thinsp;m<sup>&minus;3</sup> for annual average NO<sub>2</sub> in 2012.
Hood, C., MacKenzie, I., Stocker, J., Johnson, K., Carruthers, D., Vieno, M., & Doherty, R. (2018). Air quality simulations for London using a coupled regional-to-local modelling system. Atmospheric Chemistry and Physics, 18(15), 11221–11245. https://doi.org/10.5194/acp-18-11221-2018