Interannual variation and trends in air pollution over Europe due to climate variability during 1958–2001 simulated with a regional CTM coupled to the ERA40 reanalysis

A three-dimensional Chemistry Transport Model was used to study the meteorologically induced interannual variability and trends in deposition of sulphur and nitrogen as well as concentrations of surface ozone (O3), nitrogen dioxide (NO2) and particulate matter (PM) and its constituents over Europe during 1958–2001. The model was coupled to the meteorological reanalysis ERA40, produced at the European Centre for Medium-range Weather Forecasts. Emissions and boundary conditions of chemical compounds and PM were kept constant at present levels. The average European interannual variation, due to meteorological variability, ranges from 3% for O3, 5% for NO2, 9% for PM, 6–9% for dry deposition, to about 20% for wet deposition of sulphur and nitrogen. For the period 1979–2001 the trend in ozone, due to climate variability is increasing in central and southwestern Europe and decreasing in northeastern Europe, the trend in NO2 is approximately opposite. The trend in PM is positive in eastern Europe. There are negative trends in wet deposition in southwestern and central Europe and positive trends in dry deposition overall. A bias in ERA40 precipitation could be partly responsible for the trends. The variation and trends need to be considered when interpreting measurements and designing measurement campaigns.