Numerical modeling for the study of ozone transport in sea-breeze circulations at Sfax (Tunisia)

An ozone pollution episode typically at the mesoscale is studied for the summer period 14-15 July 1995 in the region of Sfax (Tunisia) which is submitted to strong sea-breeze circulations. At such regional scales, sea-breeze circulations are key dynamic features in the processing of natural and anthropogenic emissions in coastal, urban and industrial areas and inland, rural areas. The role of moving sea-breeze fronts on air pollution in the region of Sfax is investigated with the use of the mesoscale model Meso-NH-C (Mesoscale Non-Hydrostatic Chemistry model) in which the meteorological model Meso-NH is coupled on-line with a chemistry module. Various assumptions are presented for Meso-NH-C : e.g. compact of the chemical scheme to reduce the computational costs and the definition of procedures to fill in the lack of emission inventory data. Sensitivity studies about the impact of sea-breeze fronts on the transport and diffusion of ozone at coastal and inland areas of Sfax are presented. The Meso-NH appears to realistically simulate the sea-breeze circulations. Sea-breeze front penetration inland followed by its merging and interaction with strong continental convection caused an ozone dispersion in the period studied.