Modelled NO2 tropospheric columns at different resolutions versus OMI satellite data: analysis of a 1-year BOLCHEM simulation over Europe

Abstract

Model simulations of tropospheric NO2 vertical column density are performed using the online-coupled BOLCHEM model. Model output is compared to ozone monitoring instrument (OMI) data from the Tropospheric Emission Monitoring Internet Service (TEMIS) over Europe for the year 2007. European hot-spots (Po Valley and BeNeLux) are simulated at finer resolution and analysed separately, along with the area of Gibraltar. Standard statistical analysis reveals good model performances, even in highly polluted regions, with spatial correlation 0.90 for the whole of Europe, 0.74 for the Po Valley, 0.85 for BeNeLux and 0.79 for Gibraltar. Seasonal analysis shows some dependency on time, with lowest scores in winter, when the satellite product also suffers weaker statistical significance due to the presence of clouds. The increase in resolution is found to affect the spatial correlation more the Po Valley (+23 %) than in BeNeLux (+5 %). This difference is likely to depend on the very different meteorology of the two hot-spots.