European Soil NO_x Emissions Derived From Satellite NO₂ Observations

Abstract We introduce an innovative method to distinguish soil nitrogen oxides (NO x = NO + NO 2 ) emissions from satellite‐based total NO x emissions. To evaluate the approach, we compare the deviation between the tropospheric NO 2 concentration observed by satellite and two atmospheric composition model simulations driven by the newly estimated soil NO x emissions and the Copernicus Atmosphere Monitoring Service (CAMS) inventory. The estimated average soil NO x emissions in Europe are 1.7 kg N ha −1 yr −1 in 2019, and the annual soil NO x emissions are approximately 1.7 times larger than that of the CAMS inventory. The discrepancy originates mainly from the forests, which would mean that the soil NO x emissions over forest areas in Europe are currently underestimated by the CAMS inventory. The model evaluation indicates that the simulations driven by DECSO‐soil emissions performed significantly better than using CAMS‐soil. Overall, the simulated RMSE% of DECSO‐soil is lower than that of CAMS‐soil, approximately 6% lower in spring and 2% lower in autumn. Our method can easily be extended to other regions in the world despite having monthly variations that are very different from those in Europe.