Figure 2. August 2005 average low-pass filtered OMI tropospheric NO₂ columns (n_103,6) (top left), and the 2006–2010 August average low-pass filtered NO₂ columns normalized by August 2005 values.

Grid cells are considered if less than 5% of the original data were invalidated and the resulting probability distribution does not differ significantly from the original data (Mann-Whitney U test, p = 0.05 one-tailed)(See Supplementary Information).