Chapter 4.12 Analyzing the response of a chemical transport model to emissions reductions utilizing various grid resolutions

Within the framework of a project financed by the German EPA (Umweltbundesamt), photochemical and aerosol modelling simulations over Europe, Germany, the Federal State Brandenburg and the (agglomeration) metropolitan area of Berlin for the whole year 2002 were performed using the REM-CALGRID (RCG) model. The aim of the study was to analyze the relationships between regional and urban air quality levels and the modelled effectiveness of control measures in an urban area as a function of varying, horizontal grid resolution. The study should help to answer the question of how reliably regional scale model calculations can be used to compute air quality in urban areas. The RCG model was run at four different grid resolutions to assess the air quality in Berlin: 1. A European scale grid resolution of 0.25 degrees Latitude by 0.5 degrees Longitude (i.e., nominally about 30-km); 2. A national scale (Germany) grid having twice the resolution of grid #1 (i.e., approx. 15-km); 3. A Federal State (Brandenburg) grid having 8 times the resolution of grid #1 (i.e., approx. 4-km) and, 4. An urban (Berlin) grid having 32-times the resolution of grid #1 (i.e., approx. 1-km).