Ammonia emission estimates using CrIS satellite observations over Europe

Over the past century, ammonia (NH₃) emissions have increased with the growth of livestock and fertilizer usage. The abundant NH₃ emissions lead to secondary fine particulate matter (PM_2.5) pollution, climate change, and a reduction in biodiversity, and they affect human health. Up-to-date and spatially and temporally resolved information on NH₃ emissions is essential to better quantify their impact. In this study we applied the existing Daily Emissions Constrained by Satellite Observations (DECSO) algorithm to NH₃ observations from the Cross-track Infrared Sounder (CrIS) to estimate NH₃ emissions. Because NH₃ in the atmosphere is influenced by nitrogen oxides (NO_x), we implemented DECSO to estimate NO_x and NH₃ emissions simultaneously. The emissions are derived over Europe for 2020 on a spatial resolution of 0.2°×0.2° using daily observations from both CrIS and the TROPOspheric Monitoring Instrument (TROPOMI; on the Sentinel-5 Precursor (S5P) satellite). Due to the limited number of daily satellite observations of NH₃, monthly emissions of NH₃ are reported. The total NH₃ emissions derived from observations are about 8 Tg yr⁻¹, with a precision of about 5 %–17 % per grid cell per year over the European domain (35–55° N, 10° W–30° E). The comparison of the satellite-derived NH₃ emissions from DECSO with independent bottom-up inventories and in situ observations indicates a consistency in terms of magnitude on the country totals, with the results also being comparable regarding the temporal and spatial distributions. The validation of DECSO over Europe implies that we can use DECSO to quickly derive fairly accurate monthly emissions of NH₃ over regions with limited local information on NH₃ emissions