On the applicability of a numerical model system for calculating new European air pollution measures

A coupled meteorology-dispersion model system is used to study the dispersion of air pollutants over one continuous year. While wind and turbulence are calculated with a one-dimensional time dependent model, the time evolution of air pollutants is calculated three-dimensional. The results of the long term run of the meteorological model have been verified against surface observations and show a very good agreement in the frequency distributions as well as in time evolution. Several dispersion calculations over one year with different source characteristics and model assumptions have been carried out with the following main findings. For a realistic simulation of limit values and alert thresholds the knowledge of the time dependency of the emission is essential. Steady state dispersion calculations for specific times instead of the one year continuous run results in large differences in concentration patterns especially for elevated sources.