2026 TDep Webinar Series
NADP’s Total Deposition Science Committee invites you to our second TDep Webinar Series presentation:
Thursday, April 30th, 11-12pm EDT
Constraining Long-Term NOx Emissions over the United States and Europe using Nitrate Wet Deposition Monitoring Networks
Nitrogen oxides (NOx = NO + NO2) play a critical role in regulating tropospheric chemistry, yet NOx emission estimates are subject to large uncertainties, casting doubt on our ability to accurately model secondary pollutants such as ozone. Here, we provide an additional constraint on NOx emissions and trends using nitrate wet deposition (NWD) fluxes from the United States National Atmospheric Deposition Program (NADP) and the European Monitoring and Evaluation Programme (EMEP).
We use these NWD measurements to evaluate anthropogenic and total NOx trends and magnitudes in the global Community Emissions Data System (CEDS) emissions inventory and the GEOS-Chem chemical transport model from 1980–2020. Over both the United States and Europe, observed NWD trends track well with anthropogenic NOx emissions from the CEDS inventory until 2010, after which NWD trends level out in contrast to continued decreases in CEDS. After 2010, NWD trends are able to reproduce total NOx emissions trends when the influences of both anthropogenic and background sources are considered. Observed NWD fluxes also capture NOx emissions decreases over the 2020 COVID-19 lockdown period and are consistent with satellite and surface measurements of NO2.
We further compare modelled and observed NWD to provide an additional line of evidence for potential overestimates of anthropogenic NOx in emissions inventories. Over the United States, we find consistent overestimates of NOx emissions in CEDS in summer from 1980–2017 averaging 15–20%. Over Europe, we find that NOx is overestimated in all seasons, with the strongest average overestimates occurring in summer (175%) and fall (170%). These overestimates may be reduced by cutting anthropogenic NOx emissions by 50% in CEDS over Europe. We find that NOx emission reductions over Europe improve model ozone at the surface, reducing the model summertime ozone overestimate from 14% to 2%.
Presented by Dr. Amy Christiansen, University of Missouri – Kansas City
For more information and a link to register: https://nadp.slh.wisc.edu/tdepwebinar-2026/