Figure 1.

Spatially explicit LOTOS-EUROS (Long Term Ozone Simulation-European Ozone Simulation) (a) and Ozone Monitoring Instrument (OMI) (d) tropospheric NO₂ columns for winds coming from the north centred around Brussels according to the major up & down-wind distance of ~300 km and an across wind direction distance of ~100 km sampled on available OMI data on a 0.125° × 0.125° grid for windy conditions (>5 m s⁻¹) averaged over the period April–September 2013. The difference map between windy and calm conditions for LOTOS-EUROS (b) and OMI (e). The averaged tropospheric NO₂ columns of Brussels converted to upwind and downwind line densities LOTOS-EUROS (c) and OMI data (f) for both calm as windy conditions. The fit of the exponential function under windy conditions and the observed NO₂ pattern under calm conditions are convolved using Equations (2a) and (2b) and is given in red. The corresponding effective lifetime and R² values of the fit are also shown.