Ammonia emissions over the Benelux and neighboring regions: seasonal insights from WRF-Chem and IASI

Ammonia (NH₃) plays a key role in air quality and ecosystem impacts through its contribution to particulate matter formation and nitrogen deposition. We investigate the spatial heterogeneity and seasonality of NH₃ over Western Europe, with a focus on Benelux and neighboring regions, by combining regional chemical transport modeling, high-resolution anthropogenic emission inventories, and in situ and satellite observations.We use the WRF-Chem model at 15 km horizontal resolution over Western Europe, with a 5 km nested domain over Belgium, to simulate two periods in 2022 representative of high agricultural activity, in spring and in summer. Anthropogenic NH₃ emissions are prescribed using high-resolution (1 km) inventories, including TNO for Europe and VMM for Flanders.Model results are evaluated against surface measurements and satellite retrievals from the Infrared Atmospheric Sounding Interferometer (IASI), with a focus on the complex chemistry of NH₃ and related species across both seasons. An iterative mass-balance approach is implemented to adjust NH₃ emissions where discrepancies between modeled and observed NH₃ column concentrations are identified. We highlight and discuss the resulting changes in emission magnitude and the spatial distribution of NH₃ hotspots.