Study of the impact of low vs. high resolution meteorology on air quality simulations using the MINNI model over Italy. Massimo D'Isidoro 1 , Mihaela Mircea 2 , Lina Vitali 2 , Irene Cionni 2 , Gino Briganti 3 , Andrea Cappelletti 3 , Sandro Finardi 4 , Giandomenico Pace 5 , Luisella Ciancarella 2 , Giuseppe Cremona 2 , Antonio Piersanti 2 , Gaia Righini 2 and Gabriele Zanini 2 Abstract Modelling air quality requires the description of a large number of processes interacting each other. In order to properly model concentrations of atmospheric pollutants it is crucial to have a realistic reproduction of meteorological parameters, which can be critical in areas presenting a complex orography like the Italian peninsula. This work shows an analysis of the results obtained with the national model MINNI at two different horizontal resolutions (20 km and 4 km), for a whole year over Italy. Comparisons between modelled and observed temperature and pollutants concentrations are carried out. The prediction of temperature is improved with the increase of model spatial resolution, as it is for pollutants like NO 2 and CO, while the improvement is not always evident for O 3 concentrations. Results are discussed providing an interpretation of the observed features. Keywords: air quality modelling, high resolution, Italy, MINNI. Introduction Atmospheric composition modelling requires the description of a large number of processes for describing meteorological conditions and chemical transformations of pollutants. Emitted and transported pollutants are subjected to transformations, enhanced by sunlight (photochemistry), and removal processes (dry and wet deposition), which are closely and non-linearly interlaced with meteorological quantities. Therefore, a good description of meteorology is important to succeed in air quality forecasts. This is supposed to be even more relevant when complex morphology occurs, involving mesoscale features which make local meteorological conditions important. This work shows the effects of improved resolution on a meteorological parameter (temperature) and on some pollutants concentrations (O 3 , NO 2 and CO) as given by the Italian national model MINNI (Modello Integrato Nazionale a supporto della Negoziazione Internazionale sui temi dell’Inquinamento Atmosferico - National Integrated Model to support the international negotiation on atmospheric pollution, [6]). 1 ENEA – Technical Unit Models, Methods and Technologies for the Environmental Assessment, Bologna Research Centre, Italy.Via Martiri di Monte Sole 4, 40129 Bologna. Italy, Email: massimo.disidoro@enea.it 2 ENEA– Technical Unit Models, Methods and Technologies for the Environmental Assessment, Bologna Research Centre, Italy. 3 ENEA – Technical Unit Models, Methods and Technologies for the Environmental Assessment, Pisa Territorial Office, Italy. 4 Arianet s.r.l., via Gilino 9, 20128 Milano, Italy 5 ENEA – Technical Unit Environmental and Energy Modeling, Casaccia Research Centre, Italy