Simulation of concentration statistics with an Eulerian model - relevance of several factors to quality of results

There is a wide variety of methods for computing area-wide concentration st atistics from a number of three-dimensional dispersion simulations and seve ral parameters which affect the quality of results. Apart from the quality of the input data (emission inventory, meteorological forcing, etc.) there are additional factors e.g. the model domain size, the grid resolution, the number of simulations and the numerical methods. In order to find out the sensitivity of results to some of these items, NOX concentration statistics for the Cologne area are simulated with an EULERIAN model using several co nfigurations. The results show, that most factors have only minor relevance to the quality of results. In combination with an emission inventory, whic h is dominated by surface emissions, even for configurations with relative little expense a satisfactory agreement with observations was found for ann ual mean concentrations and 98th percentile values.