Simulation of air pollution with nested models in North Rhine-Westphalia

High resolution modeling of air pollution events requires nested models. CARLOS is a combination of two comprehensive air quality simulation models that calculate chemistry and transport on regional and local scales. Both models apply nesting techniques to describe the influx of tracers into the inner highly resolved modeling domain. High resolution emission inventories are available for the innermost nest on the large scale, which allow the separate treatment of traffic and point sources. Results of a simulation for North Rhine-Westphalia in August 1997 are presented for two nesting levels, increasing the resolution from 27 km in Central Europe to 3 km in the domain of the second nest. One result is also presented for the local scale employing two nesting levels with a resolution of 1 km and 333 m, respectively. Statistical indices are used to indicate the quality of the predictions of ozone. Comparison of observations at the stations Köln-Chorweiler and Wuppertal with modeled concentrations shows good agreement of ozone and reasonable reproduction of NO2 concentrations