Long-Term Variation in the Tropospheric Nitrogen Dioxide Vertical Column Density over Korea and Japan from the MAX-DOAS Network, 2007–2017

We investigated long-term observations of the tropospheric nitrogen dioxide vertical column density (NO2 TropVCD) from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) network in Russia and ASia (MADRAS) 2007 to 2017 at urban (Yokosuka Gwangju) remote (Fukue Cape Hedo) sites East Asia. The monthly mean NO2 TropVCD MAX-DOAS measured ~13:30 local time, which is Ozone Monitoring Instrument (OMI) overpass shows good agreement with OMI data during summer, but differences between two datasets increase winter. Theil-Sen slope trend indicate a relatively rapid gradual reduction Yokosuka Hedo), respectively, regardless season except for fall Fukue, significant changes are not observed Gwangju, Korea. In contrast, satellite reveal an all Yokosuka, where decreasing common found, suggesting that results satellites need be cautiously used investigating trends less polluted or areas. Using backward trajectories, potential source regions identified sites. spatial distribution Yokosuka. Gwangju as National Industrial Complex Yeosu Gwangyang, while transport route clearly visible because their low sensitivity proposed approach suitable identifying areas might recognized by observations.