Spatiotemporal inhomogeneity of total column NO₂ in a polluted urban area inferred from TROPOMI and Pandora intercomparisons

The spatiotemporal inhomogeneity of the total column NO2 amounts (TCN) in Seoul Metropolitan Area (SMA), Korea, was quantitatively assessed through year-round (October 2019–May 2021) TROPOMI and ground-based Pandora measurements. average TCN over SMA comparable to that major Chinese megacities, being consistently high (> 0.8 DU; Dobson Unit) during daytime (10–17 local standard time). autocorrelation scores Pandora-measured TCNs demonstrated temporal variability attributed spatial emissions within near-surface advection. Accordingly, adequate collocation range for measurements intercomparison with satellite sensors considered be ± 5 min avoid significant uncertainty from (RMSE < 0.1 DU, R2 > 0.96). showed better agreement conventionally collocated (0.73 0.76, 26–29% negative bias) than other two (OMI OMPS) its highest resolution. application wind-based revealed a greater bias on upwind side, which less affected by anthropogenic urban area, downwind increasing distance pixel most critical factor deteriorating scores. FRESCO-S cloud algorithm update FRESCO-wide yielded general increase TCN, especially partially cloudy pixels, leaving only 11% (downwind) 29% (upwind) coincident Furthermore, method distribution pattern NOX (NO + NO2) SMA, emission sources northeastern southeastern sides site Seoul.