Figure 7.17. Tropospheric column NO₂ from (a) satellite measurements and (b) atmospheric chemistry models. The maps represent ensemble average annual mean tropospheric NO₂ column density maps for the year 2000. The satellite retrieval ensemble comprises three state-of-the-art retrievals from GOME; the model ensemble includes 17 global atmospheric chemistry models. These maps were obtained after smoothing the data to a common horizontal resolution of 5° × 5° (adapted from van Noije et al., 2006).