A modelling system for predicting urban air pollution: model description and applications in the Helsinki metropolitan area

We have developed a modelling system for evaluating the traffic volumes, em issions from stationary and vehicular sources, and atmospheric dispersion o f pollution in an urban area. The dispersion modelling is based on combined application of the urban dispersion modelling system (UDM-FMI) and the roa d network dispersion model (CAR-FMI). The system includes also a meteorolog ical pre-processing model and a statistical and graphical analysis of the c omputed time series of concentrations. The modelling system contains a meth od, which allows for the chemical interaction of pollutants, originating fr om a large number of urban sources. This paper presents an overview of the modelling system and its application for estimating the NOx and NO2 concent rations in the Helsinki metropolitan area in 1993. A companion paper addres ses comparison of model predictions with the results of an urban measuremen t network. This modelling system is an important regulatory assessment tool for the national environmental authorities. (C) 2000 Elsevier Science Ltd. All rights reserved.