Comparison of four years of air pollution data with a mesoscale model

Air quality within the European Union (EU) is controlled by the Member States' monitoring networks. In this study, measured data is compared with the EURAD (EURopean Air pollution Dispersion) model system diagnostic output Simulations for the German state North Rhine-Westphalia (NRW) with a horizontal grid resolution of 5 km x 5 km are analyzed. The comparison is performed for NO2, O-3, and PM10, for the 4-year time period from 2002 through 2005. Although the spatial representativity of data of the two systems differs, the analyzed temporal variability of the averages shows good agreement of modeled and observed concentrations for all three parameters. This confirms the applicability of the EURAD model to mesoscale air quality assessment. Discrepancies between the model and observed data occurred at low concentrations close to the detection limits of the analyzers, for high O-3 concentrations in summer, and for PM10 before 2004, when earlier versions of the MM5 meteorological module and of the emission inventory were used. Possible causes of O-3 overprediction and NO2 underprediction preferably showing up in summer are considered. It is found that modeled O-x = O-3 + NO2 leads to better representation of the observations than the individual species themselves. The model performance can probably be increased by further development of the emission inventories and more accurate land use data. These input data seem to be the main reason for deviations between observations and model results. (C) 2012 Elsevier B.V. All rights reserved