Comment on egusphere-2025-5926
Abstract
Abstract. Ammonia (NH3) and nitrogen dioxide (NO2) are key components of reactive nitrogen, strongly affecting air quality and ecosystem health. However, long-term constraints on ammonia emissions and deposition remain uncertain due to sparse in situ measurements and limitations of individual satellite products. We jointly assimilate five years (2018–2022) of NH3 and NO2 satellite observations over the Netherlands to improve constraints on reactive nitrogen concentrations, emissions, and deposition. NH3 retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) and the Cross-Track Infrared Sounder (CrIS) are combined with NO2 observations from the TROPOspheric Monitoring Instrument (TROPOMI) within the LOTOS-EUROS chemical transport model using a Local Ensemble Transform Kalman Filter. The co-assimilation produces coherent year-to-year adjustments in modeled NH3 concentration, emission, and deposition fields. Validation against measurements from the Dutch National Air Quality Monitoring Network (LML) shows reduced biases, clearer diurnal cycles, and improved correlations. Sensitivity experiments demonstrate that including TROPOMI NO2 alongside IASI and CrIS NH3 yields the lowest NH3 surface bias versus LML, highlighting the added value of coupling chemically related satellite observations. Comparisons with monthly Measurements of Ammonia in Nature (MAN) observations showed improved correlations but persistent spatial biases due to representativeness differences, while MAN sensors co-located with LML stations exhibited consistent improvements. These results demonstrate that co-assimilating complementary satellite observations can substantially improve constraints on ammonia emissions and deposition, with direct relevance for air-quality assessment and nitrogen policy applications.
Authors 11
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Tyler Wizenberg corresponding
Netherlands Organisation for Applied Scientific Research
Affiliation as printed
Air Quality & Emissions Research, TNO, Utrecht, the Netherlands
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Leiden University · Netherlands Organisation for Applied Scientific Research
Affiliation as printed
Air Quality & Emissions Research, TNO, Utrecht, the Netherlands
Institute of Environmental Sciences, Universiteit Leiden, Leiden, the Netherlands
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Netherlands Organisation for Applied Scientific Research
Affiliation as printed
Air Quality & Emissions Research, TNO, Utrecht, the Netherlands
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Environment and Climate Change Canada
Affiliation as printed
Environment & Climate Change Canada (ECCC), Toronto, Canada
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Affiliation as printed
Université libre de Bruxelles (ULB), BLU-ULB research Center, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels, Belgium
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Affiliation as printed
Université libre de Bruxelles (ULB), BLU-ULB research Center, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels, Belgium
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Université Libre de Bruxelles · Royal Belgian Institute for Space Aeronomy
Affiliation as printed
Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
Université libre de Bruxelles (ULB), BLU-ULB research Center, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels, Belgium
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Royal Netherlands Meteorological Institute
Affiliation as printed
Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
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National Institute for Public Health and the Environment
Affiliation as printed
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
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National Institute for Public Health and the Environment
Affiliation as printed
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
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Netherlands Organisation for Applied Scientific Research · Freie Universität Berlin
Affiliation as printed
Air Quality & Emissions Research, TNO, Utrecht, the Netherlands
Freie Universiteit Berlin (FUB), Berlin, Germany
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