EVALUATION OF THE CHEMISTRY-TRANSPORT MODEL MECTM USING TRACT-MEASUREMENTS - EFFECT OF DIFFERENT SOLVERS FOR THE CHEMICAL MECHANISM

摘要

This study deals with the determination of the uncertainty of the predicted concentration of selected key trace gases due to the applied numerical solver for the chemical mechanism in the lower troposphere. It could be seen that the numerical solution technique for the chemistry has an effect on the overall model result. The HYBRID-solver improves the simulated NOx concentration values while O3 concentrations are only slightly affected. The discrepancies between the model results and the corresponding measurements for the target quantities NO_x and O_3 could, however, only partly explained by the change of the numerical solver. Since the chosen evaluation episode was transport dominated the investigated effect on the change of the pollutant concentrations is small compared to transport related changes. Therefore, the observed differences between measurements and model results can be explained to a large extend by inaccuracies of the lateral boundary values and of the predicted meteorological parameters such as wind direction and wind speed (Lenz et al., 2000) as well as by the treatment of elevated point emissions. The significance of the shown results are mainly reached by the employment of quality insured high resolution aircraft measurements.