Proceedings of the 11 th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes Page 48 MODELLING ATMOSPHERIC PARTICLES IN THE IBERIAN PENINSULA AND BALEARIC ISLANDS Marta G. Vivanco, Inmaculada Palomino, Fernando Martín and Magdalena Palacios. Air Pollution Unit. CIEMAT. Madrid, Spain INTRODUCTION Besides ozone and nitrogen oxides, exceedances of air quality standards for other pollutants, such as particulate matter, are being recorded in Spain. Studies and measurements during the last years indicate that PM10 is the pollutant with a higher number of air quality standard exceedances in Spain. Many of the exceedances are caused by natural events such as Saharan dust transport. Models have become a useful tool in air quality management, since European legislation determine the obligation to evaluate air quality and improve air quality in polluted areas. For this purpose, models must be able to reproduce all the physical and chemical processes affecting pollutant behaviour in the atmosphere. In this paper we include the results of the application of the CHIMERE model to simulate PM10 and PM2.5 in Spain for 2004. Results were compared with measurements of Spanish stations. MODELLING SETUP Simulations were carried out using a regional version of the CHIMERE chemistry-transport model. This version (V200603par-rc1) calculates the concentration of 44 gaseous species and both inorganic and organic aerosols of primary and secondary origin, including primary particulate matter, mineral dust, sulphate, nitrate, ammonium, secondary organic species and water. A detailed description of the model configuration and performances over Europe are presented in previous studies (Bessagnet et al., 2004; Vautard et al., 2003). Because of the possible influence of long range pollutant transport the model system was first used at European scale over a domain ranging from 10.5W to 22.5E and from 35N to 57.5 N with a 0.5 degree horizontal resolution and 14 vertical sigma-pressure levels extending up to 500 hPa. Downscaling was done for the Iberian Peninsula using a fine-scale domain with a 0.2 degree resolution and a one-way nesting procedure where coarse-grid simulations force the fine-grid ones at the boundaries without feedback. The MM5 model (Grell et al., 1995) was used to obtain meteorological input fields. The simulations were carried out for a coarse domain and a finer one, with respective resolutions of 36 Km and 19 Km. MM5 simulations are forced by the National Centres for Environmental Prediction model (GFS) analyses at both scales, using a nudging procedure. For both domains emissions were derived from the annual totals of the EMEP database for 2004 (Vestreng et al., 2005). Original EMEP emissions were disaggregated taking into account the land use information, in order to get higher resolution emission data. Boundary conditions for the coarse domain were provided from monthly climatology from LMDz- INCA model (Hauglustaine et al., 2004) for gases concentrations and from GOCART model (Chin et al., 2002) for particulate species, as described in Vautard et al. (2005).