Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 2 2004 10.5194/acpd-4-1855-2004 http://www.atmos-chem-phys-discuss.net/4/1855/2004/ http://www.atmos-chem-phys-discuss.net/4/1855/2004/acpd-4-1855-2004.html http://www.atmos-chem-phys-discuss.net/4/1855/2004/acpd-4-1855-2004.pdf 1855 1885 2004-03-24 Evaluation of two ozone air quality modelling systems S. Ortega sortega@am.ub.es M. R. Soler J. Beneito D. Pino Department of Astronomy and Meteorology, University of Barcelona, Avd. Diagonal 647, 08028 Barcelona, Spain Institute for Space Studies of Catalonia, Edifici Nexus 2, Gran Capità 2–4, 08034 Barcelona, Spain Applied Physics Departament, Technical University of Catalonia, Avd. Del Canal Ol&#x00ED;mpic s/n, 08860 Castelldefels, Barcelona, Spain The aim of this paper is to evaluate and compare two models of ozone air quality used in the north of Spain near the metropolitan area of Barcelona. As the focus of the paper is the comparison of the two systems, we do not attempt to improve the agreement by adjusting the emission inventory or model parameters. <br><br> The first model, or forecasting system, is made up of three modules. The first module is a mesoscale model (MASS). This provides the initial condition for the second module, which is a nonlocal boundary layer model based on the transilient turbulence scheme. The third module is a photochemical box model (OZIPR), which is applied in Eulerian and Lagrangian modes and receives suitable information from the two previous modules. The model forecast is evaluated against ground base stations during summer 2001. The second model is the MM5/UAM-V. This is a grid model designed to predict the hourly three-dimensional ozone concentration fields. The model is applied during an ozone episode that occurred between 21 and 23 June 2001. Our results reflect the good performance of the two modelling systems when they are used in a specific episode.