A 3D REGIONAL-SCALE PHOTOCHEMICAL AIR-QUALITY MODEL APPLICATION TO A 3 DAY SUMMERTIME EPISODE OVER PARIS

This paper presents AZUR, a 3D Eulerian photochemical air quality mode l for the simulation of air pollution in urban and semi-urban areas. T he model tracks gas pollutant species emitted into the atmosphere by t ransportation and industrial sources, it computes the chemical reactio ns of these species under varying meteorological conditions (photolysi s, pressure, temperature, humidity), their transport by wind and their turbulent diffusion as a function of air stability. It has a modular software structure which includes several components dedicated to spec ific processes: -MERCURE, a meso-scale meteorological model to compute the wind field, turbulent diffusion coefficients, and other meteorolo gical parameters. It is a 3D regional scale model accounting for diffe rent ground types and urban densities. It includes a complete set of p hysical parameterizations in clear sky. -MIEL, an emission inventory m odel describing the pollutant fluxes from automotive transportation, d omestic and industrial activities. This model includes a mobile source inventory based an road vehicle countings together with global inform ation on transportation fluxes extracted from statistical population d ata. It uses specific emission factors representative of the vehicle f leet and real driving patterns. -MoCA a photochemical gas phase model describing the chemistry of ozone, NOx, and hydrocarbon compounds. Thi s model, with 83 species and 191 reactions, is a reduced mechanism wel l adapted to various air quality conditions (ranging from urban to rur al conditions). For interpretative reasons, the identity of primary hy drocarbons is preserved. -AIRQUAL, a 3D Eulerian model describing the transport by mean wind flux and air turbulent diffusion of species in the atmosphere, associated with a Gear type chemical equation solver. The model has been applied to a 3-day summertime episode over Paris ar ea. Simulation results are compared to ground level concentration meas urements performed by the local monitoring network (Airparif).