Comparison and evaluation of modelled and GOME measurement derived tropospheric NO₂ columns over Western and Eastern Europe

International audienceWe present the results of a first comparison of the tropospheric NO2 column amounts derived from the measurements of the Global Ozone Monitoring Experiment (GOME) with the simulated data from a European scale chemistry transport model (CTM) which is distinctive from existing global scale CTMs in higher horizontal resolution and more detailed description of the boundary layer processes and emissions. We employ, on the one hand, the newly developed extended version of the CHIMERE CTM, which covers both Western and Eastern Europe, and, on the other hand, the most recent version (Version 2) of GOME measurement based data-products, developed at the University of Bremen. We evaluate our model with the data of ground based monitoring of ozone and verify that it has a sufficiently high level of performance, which is expected for a state-of-the-art continental scale CTM. The major focus of the study is on a systematic statistical analysis and a comparison of spatial variability of the tropospheric NO2 columns simulated with CHIMERE and derived from GOME measurements. The analysis is performed separately for Western and Eastern Europe using the data for summer months of 1997 and 2001. In this way, we evaluate the upper limits to uncertainties of spatial distributions of the considered data. Specifically, for Western Europe, it is found that the mean relative (multiplicative) random errors of the GOME measurement derived and simulated data averaged over the summer seasons considered do not exceed 25% and 35%, respectively, and the mean absolute (additive) errors are less than 3·1014 mol/cm2. The upper limits for the multiplicative errors for Eastern Europe are shown to be smaller than those for Western Europe and do not exceed 15% and 24% for NO2 columns from GOME and CHIMERE, respectively. The relative contribution of the additive errors is found to be much larger for Eastern Europe, but their mean absolute values are less than 2·1014 mol/cm2