A modelling system for predicting urban air pollution:: comparison of model predictions with the data of an urban measurement network in Helsinki

We have developed a modelling system for predicting the traffic volumes, emissions from stationary and vehicular sources, and atmospheric dispersion of pollution in an urban area. A companion paper addresses model development and its applications. This paper describes a comparison of the predicted NOx and NO2 concentrations with the results of an urban air quality monitoring network. We performed a statistical analysis concerning the agreement of the predicted and measured hourly time series of concentrations, at four monitoring stations in the Helsinki metropolitan area in 1993. The predicted and measured NO2 concentrations agreed well at all the stations considered. The agreement of model predictions and measurements for NOx and NO2 was better for the two suburban monitoring stations, compared with the two urban stations, located in downtown Helsinki.