Spatial variation of modelled and measured NO, NO₂ and O₃ concentrations in the polluted urban landscape – relation to meteorology during the Göte-2005 campaign

Abstract. Knowledge about temporal and spatial variations of the O₃ and NO_x relationship in the urban environment are necessary to assess the exceedance of air quality standards for NO₂. Both reliable measurements and validated high-resolution air quality models are important to assess the effect of traffic emission on air quality. In this study, measurements of NO, NO₂ and O₃ concentrations were performed in Gothenburg, Sweden, during the Göte-2005 campaign in February 2005. The aim was to evaluate the variation of pollutant concentrations in the urban landscape in relation to urban air quality monitoring stations and wind speed. A brief description of the meteorological conditions and the air pollution situation during the Göte-2005 campaign was also given. Furthermore, the Air Pollution Model (TAPM) was used to simulate the NO_x-regime close to an urban traffic route and the simulations were compared to the measurements. Important conclusions were that the pollutant concentrations varied substantially in the urban landscape and the permanent monitoring stations were not fully representative for the most polluted environments. As expected, wind speed strongly influenced measured pollutant concentrations and gradients. Higher wind speeds dilute NO₂ due to stronger dispersion; while at the same time vertical transport of O₃ is enhanced, which produces NO₂ through oxidation of NO. The oxidation effect was predominant at the more polluted sites, while the dilution effect was more important at the less polluted sites. TAPM reproduced the temporal variability in pollutant concentrations satisfactorily, but was not able to resolve the situation at the most polluted site, due to the local scale site-specific conditions.