4.1 The model domain

**Figure 8:** Digital elevation model of the model domain on the Swiss Plateau with the Alps in the Southeast and the Jura mountains in the Northwest. Thin lines represent rivers and lake shores, bold lines indicate major traffic axes (highways or motor-ways). Horizontal extent is 200 km `x` 90 km, grid cell size is 2 km. For the model, the topography was re-sampled to a resolution of two kilometers and to be rounded to the vertical levels of the model.
$\begin{figure} \begin{center} \leavevmode \epsfxsize=\textwidth \epsffile{domain.eps} \end{center} \end{figure}$

Within the framework of the POLLUMET summer smog investigation program an intensive field measurement campaign was carried out on the Swiss Plateau during 29 - 30 July 1993 (Neininger; 1993). To compare the model output with reality and to give an interpretation of the concentrations found during that episode, a simulation of these days was carried out and compared with meteorological and chemical measurements. Figure 8 shows the model domain extending from Payerne in the West to Frauenfeld in the East (length of domain is 200 km). It is limited by the Alps in the Southeast and by the Jura mountains in the Northwest (width of domain is 90 km). The most densely populated areas within the domain can be found around the cities of Bern, and Zürich. The lowlands have generally more inhabitants (and pollution) than the mountains, which are only sparsely populated. The horizontal grid cell size was 2km x 2km . The original topography therefore had to be simplified, to be suitable for the model.