_________________________________________________________________________________ BALWOIS 2008 – Ohrid, Republic of Macedonia – 27 - 31 May 2008 1/6 Long-term meteorological mesoscale RAMS simulations over Northern Italy for air quality assessments Ekaterina BATCHVAROVA*, Claudio CARNEVALE**, Enrico PISONI** and Giovanna FINZI** *National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, Tzarigradsko shaussee, Sofia 1784, Bulgaria, e-mail: Ekaterina.batchvarova@meteo.bg ; ** Department of Electronics for Automation, Faculty of Engineering, University of Brescia, Italy Abstract Exceeding the air quality standards set by the European Union for ground-level concentrations of ozone and PM has significant impact on human health and vegetation. This is a well-known problem in Northern Italy, where high anthropogenic emissions and frequent stagnant meteorological conditions bring to very high concentrations of PM in winter and of ozone in summer. Another peculiarity of the Northern Italy domain is the fact that the non-attainment of secondary pollution standards is not restricted to urban areas but often occurs away from cities, at mesoscale. For this reason, in a scenario analysis framework, it is necessary to evaluate emission control strategies considering accurate deterministic simulations performed with complex modeling systems. Meteorological models are an important part of the deterministic modeling systems. The meteorological variables rule pollutants advection, diffusion, wet deposition, chemical reactions and therefore need to be adequately simulated. Within an HPC-EUROPE (Pan-European Research Infrastructure on High Performance Computing) cooperation project the meteorological conditions over Northern Italy were simulated using RAMS4.4 in parallel mode for the year 2004, creating a database for further air quality assessments. First results of the study and comparisons between modeled and measured meteorological parameters are presented and discussed in the paper. Key words: Mesoscale meteorological models, RAMS, Northern Italy, Atmospheric Boundary Layer, Air pollution Introduction The Italian environmental laws implementing the EU Environmental Directives, assign to the Regions’ authorities the task of Air Quality Assessment. The laws suggest the integrated application of different tools: monitoring, emission inventory and dispersion modeling. To fulfil such requests, integrated air quality assessments have to be performed. The basic part of the air quality modeling assessments is the deterministic meteorological modeling using up to date meso meteorological models. According to the outlined concept the main elements of air quality management systems could be grouped in environmental information (I) (data gathering patterns: monitoring, scientific investigations, statistics, modeling (Volta and Finzi, 2006; Carnevale et al., 2008); data processing and storage in databases; reporting: operationally, monthly, annually etc.), decision making (II), raising of environmental awareness with informing of society and possible involvement (Carnevale et al., 2007) of stakeholders (III) as well as different actions (IV) to be performed in order to improve or maintain the air quality. There is currently little comprehensive regulatory guidance on the techniques and approaches for evaluating meteorological model performance and how to systematically evaluate model options such as horizontal grid size, vertical layer structure and other model parameters. The EU regulatory guidance requires that dispersion modeling is conducted for a minimum of one year, respectively such long-term meteorological modeling is to be performed as well. The meteorological fields created for these applications involve large amounts of data that is difficult to summarize and evaluate thoroughly. Often the meteorological fields generated to support dispersion modeling are not subject to any routine regulatory evaluation, although they are certainly a critical component of any dispersion modeling study. This collaborative study within the HPC-EUROPE (Pan-European Research Infrastructure on High Performance Computing) is devoted to the evaluation of the performance of a mesoscale meteorological model (RAMS4.4) over the area of Northern Italy for the year 2004. In this paper a comparison of modelled and measured meteorological fields is performed for a station located close to Milan, a city often affected by severe secondary pollution episodes (Vecchi et al., 2004; Gabusi et al., 2005).