Urban air dispersion model of a mid-sized city. Validation methodology LÍGIA T. SILVA, JOSÉ F.G. MENDES, RUI A.R. RAMOS Department of Civil Engineering, School of Engineering University of Minho Campus de Gualtar, 4710-057 Braga PORTUGAL lsilva@civil.uminho.pt http://www.civil.uminho.pt Abstract: Viana do Castelo is a mid-sized city located on the northwest Portuguese seaside, which undertook the challenge of developing an environmental program leading to the integration in the Healthy Cities European Network. Within this program includes prediction of pollutant concentration for NO2, CO, PM10, O3 and C6H6. This paper presents the methodology developed to validate the modelled results. Predicted concentrations were compared against measured concentrations of a chosen pollutant: Carbon Monoxide, CO. The methodology adopted was based in BOOT statistical approach. Five comparison statistics were calculated for three test points in order to find out the quality of the modelled results. Additionally, a hourly profile of predicted versus measured concentrations was developed. Key-Words: Air pollution modelling; Validation 1 Introduction The urban argument assumes currently an extreme level of relevance for the governments and the society in general, due to the exponential increase of people living in cities and the consequent associated degradation of quality of life growth is continuously applying pressures over resources, infrastructures and facilities, affecting negatively the standard of living in cities [1]. In this context, evaluating and monitoring the urban environmental quality has become a main issue particularly important when considered as a decision-support tool that contributes to more liveable and sustainable cities. Viana do Castelo is a mid-sized city located on the northwest seaside, which undertook the challenge of developing an environmental program leading to the integration in a Healthy Cities European Network. The Healthy Cities Project is, today, a worldwide movement, having on its basis the concept Health for All (HFA). In 1986 the World Health Organization (WHO) selected eleven cities in order to demonstrate that the new approaches in public health defended by HFA worked in practice. This is how the concept Healthy Cities was born. Within this program, the identification of urban air pollution levels and people exposure was considered a priority. In line with most of the EU countries, Portuguese specific legislation requires local government authorities to manage air quality in their areas, with the aim of achieving the objectives laid out in Table 1. Table 1 – Portuguese annual limit concentration for the protection of human health [2,3] Pollutant Averaging period Value Nitrogen dioxide (NO2) Calendar year 40 μg/m3 Particulate matter (PM10) Calendar year 40 μg/m3 Ozone (O3) 8 hours (rolling average) 110 μg/m3 Benzene (C6H6) Calendar year 5 μg/m3 Carbon Monoxide (CO) 8 hours (max) 10 mg/m3 The work developed in Viana do Castelo used local emission inventories to model concentrations of the key pollutants in the city, and the outputs included time series of predicted concentrations which were compared with measured data at monitoring sites. Predicted concentration includes time series at locations coincident with monitors and contour maps over the total calculation area. This paper presents the methodology developed to validate the predicted results. Both spatial and temporal validations were undertaken. WSEAS TRANSACTIONS on ENVIRONMENT and DEVELOPMENT Ligia T. Silva, Jose F. G. Mendes, Rui A. R. Ramos ISSN: 1790-5079 1 Issue 1, Volume 6, January 2010