A comparison of the impact of TROPOMI and OMI tropospheric NO<sub>2</sub> on global chemical data assimilation

Abstract. This study gives a systematic comparison of the Tropospheric Monitoring Instrument (TROPOMI) version 1.2 and Ozone (OMI) QA4ECV tropospheric NO2 column through global chemical data assimilation (DA) integration for period April–May 2018. DA performance is controlled by measurement sensitivities, retrieval errors, coverage. The smaller mean relative observation errors 16 % in TROPOMI than OMI over 60? N–60? S during 2018 led to larger reductions root-mean-square error (RMSE) against assimilated measurements (by 54 %) 38 %). Agreements independent surface, aircraft-campaign, ozonesonde were also improved compared control model simulation 12 %–84 7 %–40 ozone), which more obvious those many cases 2 %–70 1 %–22 ozone) due better capturing spatial temporal variability DA. estimated total NOx emissions 15 lower DA, with %–23 regional emissions, line observed negative bias product product. can provide city-scale emission estimates, within 10 differences other high-resolution analyses several limited areas, while providing globally consistent analysis. These results demonstrate that improves ozone, would benefit studies on detailed variations ozone nitrate aerosols evaluation bottom-up inventories.