Numerical Modelling of Troposferic Ozone in Catalunya

The aim of this paper is to evaluate the ability of two different modelling systems to simulate high values of ozone concentration in typical summer episodes which take place in Catalonia, located in the north-east part of Spain. The first model, or forecasting system, is a box model made up of three modules. The first module is a mesoscale model (MASS), which provides the initial condition for the second module, a non-local 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 receiving suitable information from the two previous modules. The model forecast is applied to different areas of Catalonia and evaluated during the springs and summers of 2003 and 2004 against ground base stations. The second model is MM5/UAM-V, a grid model designed to predict the hourly three-dimensional ozone concentration fields. The model is applied during an ozone episode occurred between 21 and 23 June 2001 at only one area, which is characterized by complex topography and a peculiar meteorological condition favouring high ozone concentration values. Evaluation results and model comparison for this specific episode show a good performance of the two modelling systems.