NH3 levels over Europe during COVID-19 were modulated by changes in atmospheric chemistry

The coronavirus outbreak in 2020 had a devastating impact on human life, albeit a positive effect for the environment, reducing primary atmospheric constituents and improving air quality. Here we present, for the first time, inverse modelling estimates of ammonia emissions during the European lockdowns of 2020 based on satellite observations. Ammonia has a strong seasonal cycle; it mainly originates from agriculture, which was influenced insignificantly by the lockdowns, as practically agricultural activity never ceased. The key result is a -0.7% decrease in emissions in the first half of 2020 compared to the same period in 2016–2019 attributed to restrictions related to the global pandemic or an abrupt -9.8% decrease due to reductions in the traffic-related precursors of atmospheric acids, with which ammonia reacts to form secondary aerosols. When comparing emissions before, during and after lockdowns, the typical seasonal trends of ammonia prevail. However, when reductions in the prec..., - FLEXPART v10.4 sensitivities for 6 model levels using chemistry loss after taking into account changes in emissions of NOx and SO2 in the calculations (see also associated paper): AVE_FOOTPRINT_L1_chem.nc, AVE_FOOTPRINT_L2_chem.nc, AVE_FOOTPRINT_L3_chem.nc, AVE_FOOTPRINT_L4_chem.nc, AVE_FOOTPRINT_L5_chem.nc, AVE_FOOTPRINT_L6_chem.nc
- FLEXPART v10.4 sensitivities for 6 model levels using chemistry loss after taking into account changes in emissions of NOx and SO2 in the calculations (see also associated paper): AVE_FOOTPRINT_L1_nochem.nc, AVE_FOOTPRINT_L2_nochem.nc, AVE_FOOTPRINT_L3_nochem.nc, AVE_FOOTPRINT_L4_nochem.nc, AVE_FOOTPRINT_L5_nochem.nc, AVE_FOOTPRINT_L6_nochem.nc
- Different surrounding estimates of posterior emissions covering 2°, 3° and 4° from each grid-cell: 2deg.tar.gz, 3deg.tar.gz, 4deg.tar.gz
- Performance calculations for the prior and posterior emissions against the dependent observations (CrIS): Correction_R4.tar.gz
- Forward simulations with FLEXPART v10.4 using...,