Inversion-based assessment of anthropogenic NO x emission changes in Ukraine during the 2022–2023 war using TROPOMI satellite data

Abstract. The outbreak of the Russia–Ukraine war in 2022 brought a huge impact on the Ukrainian society. We utilized TROPOMI nitrogen dioxide (NO2) observations to constrain the Emissions Database for Global Atmospheric Research (EDGAR) inventory and inverted daily anthropogenic nitrogen oxides (NOx) emissions in Ukraine from 2019 to 2023. Our results reveal a 15 % reduction in NOx emissions during the 2022 war and an 8 % reduction in 2023, both substantially exceeding the decrease caused by the COVID-19 pandemic. Emission anomalies closely tracked the timing and location of major military actions, highlighting the sensitivity of NOx emissions to conflict-related disruptions. Regionally, Eastern Ukraine experienced larger reductions in NOx emissions in both 2022 and 2023 by 29 % and 17 %, respectively, due to direct damage from frontline military operations. In contrast, Western Ukraine experienced a relatively modest emission reduction of only 8 % in 2022 with emissions increasing in some regions. In 2023, the emissions increased in most western regions. After the outbreak of the war, the industrial sector experienced the largest reductions in NOx emissions, with decreases of 34 % and 24 % in 2022 and 2023, respectively, followed by the residential sector, which declined by 23 % and 18 % respectively. War activities also emitted large amounts of NOx, and such emissions partially offset the emission reduction caused by the impact of war on socio-economic. By filtering out high-frequency emission fluctuations induced by wartime activities through Locally Estimated Scatterplot Smoothing, our results indicate that war-related emissions may have offset approximately 8 % and 10 % of the anthropogenic NOx reductions in 2022 and 2023, respectively. After removing the war-related emissions, the inverted emission declines exhibit strong agreement with bottom-up emission inventories and reported economic performance metrics. These findings provide new insights into the environmental and socio-economic impacts of armed conflict.