Comparison of variability and change rate in tropospheric NO2 column obtained from satellite products across China during 1997-2015

Tropospheric NO2 column (TNC) products retrieved from five satellites including GOME/ERS-2 (H, 1997-2002), SCIAMACHY (S, 2003-2011), OMI (O, 2005-2015), GOME-2/METOP_A (A, 2007-2013) and GOME-2/METOP_B (B, 2013-2015) were compared in terms of their spatiotemporal variability and changes over China. The temporal series of H suggested an increasing trend of TNC from 1997 to 2002, those of S, O and A revealed further increasing trends until the highest level of TNC was reached in 2011, but decreasing trends were detected by those of O and B from 2011 to 2015. Seasonally, TNC was the highest in winter and the lowest in summer. Variability and changes from satellite TNC products are also analyzed in different regions of China. Spatially, it was the highest in North China and the lowest in Tibetan Plateau based on five datasets. Overall, TNCs from A, B and S were higher than that from O; and TNC from S was larger than that from A at the country level. The higher TNC the region has, the larger difference satellite products would show. However, different datasets reached a good agreement in the spatial pattern of trends in TNC with highly significant increasing trends detected in North China.