Simulation of the air quality during a field study for the city of Graz

The research project DATE Graz (Dispersion of Atmospheric Trace Elements taking the city of Graz as an example) aimed at the investigation of mesoscale γ pollution dispersion of a city in complex terrain. The winter episode investigated here was characterised by an anticyclonic fair weather situation. Local wind systems developed together with strong temperature inversions. During such an episode air quality is dominated by emissions from within the city. The city of Graz is situated in the southeast of the Alps in the transition area of mountainous to flat land. The city itself is located in the valley of the river Mur, which forms a basin surrounded by small mountains. In order to understand the emitter–receptor relationship a mesoscale dispersion model was applied for the simulation of air quality during the winter episode. Input for the simulation was the emission inventory and extensive meteorological measurement data. Results of the simulation reflect the distinct patterns of daily variations of air quality level measured. The influence of meteorology, emission patterns and chemical reactions are evident and can be qualitatively and partly quantitatively simulated by the model. A validation attempt was made using air quality data from the monitoring network. The introduction shows the importance of anticyclonic fair weather conditions on pollution dispersion in mountainous regions. Section 2 describes the meteorological situation and the instrumentation during the winter measurement campaign. Section 3 deals with the simulation model, initial and boundary conditions and the emission inventory for the city. In Section 4 the simulation results are compared to measurements. Finally conclusions are drawn.