Inter-annual Variations of Ozone and Nitrogen Dioxide Over Europe During 1958–2003 Simulated with a Regional CTM

Inter-annual variability of surface ozone (O₃) and nitrogen dioxide (NO₂) over Europe has been studied over the period 1958–2003 using a three-dimensional Chemistry-Transport Model coupled to meteorological data from the ERA40 data set produced at the European Centre of Medium-range Weather Forecasts (ECMWF). Emissions and boundary conditions were kept at present levels throughout the simulation period. It was found that the annual mean NO₂ concentration varies between ±50% and the summer mean O₃ concentration varies between −10 and +20 percent (%) compared to the 46-year average over the model domain. There is also variation in ozone and NO₂ over longer time scales. The last 22 years display high concentrations of ozone in central and south-western Europe and low concentrations in north-eastern Europe. The first 22 years display very high concentrations of NO₂ over the North Sea. There is indication of trends in ozone and nitrogen dioxide but this has to be investigated further. Such information is one factor that should be taken into account when considering future control strategies.