As part of an interdisciplinary Collaborative Research Center (SFB 419) the project ‘Origin, Transformation and Transport of Air Pollutants – Investigation of Reduction Strategies by Simulation’ is performed at the University of Cologne. A main objective of this project is to work out the impact of spatially and temporally strongly varying emissions of individual traffic on urban air quality. For that purpose a high resolution dynamic traffic model is applied which is coupled with nested models of the atmospheric chemistry and transport.

To describe the complex relationship between release and transmission of gaseous pollutants in the atmosphere the model system CARLOS (Chemical and Atmospheric transport in Regional and LOcal Scale) was developed. This model system has multiple-nesting capability which allows to account for large scale features while simulating local scale structures in nested regions. On the regional scale the meteorological model MM5 is used as input to the chemistry transport model (CTM2). The results in return serve as boundary conditions for the small scale high resolution models (FOOT3D/CTM2F), which are capable to simulate flow and pollution pattern e.g. on the scale of urban districts.

Presently on local scale special emphasis is given to nitric oxides (NO_x) emitted by vehicles in context with summertime ozone (O₃) production. A dynamic traffic model is employed to calculate highly resolved emission inventories for pollutants generated by traffic. By simulating individual routes for single vehicles in a road network the model pays regard to e.g. interactions of the road user and even traffic jams. The design of this model also enables studying the impact of local administrative regulations or municipal development planning on traffic flow and the related emissions.

For first studies and model testing a period of August 1997 with high ozone mixing ratios in the state North-Rhine Westphalia in Germany was chosen and simulated. This base case scenario acts as starting point for further investigations with fictitious but realistic traffic scenarios (e.g. speed limitations) in the Cologne area. In addition a second scenario, based on the alteration of industrial emissions connected with the transition from presently operated large lignite power-stations to communal heating power-stations, will be performed.

Future focus will be laid upon an analysis of the impact of predicted changes of industrial or traffic induced emissions on air quality in an industrial conurbation. This will be realized together with other participants of the SFB 419, e.g. scientists of medicine, economics and sociology, so that suggestions for an improvement of air quality could be evolved.