Preprints
https://doi.org/10.5194/egusphere-2025-3915
https://doi.org/10.5194/egusphere-2025-3915
05 Sep 2025
 | 05 Sep 2025
Status: this preprint is open for discussion and under review for Geoscientific Model Development (GMD).

Evaluation of atmospheric sulfur dioxide simulated with the EMAC (version 2.55) Chemistry-Climate Model using satellite and ground-based observations

Ismail Makroum, Patrick Jöckel, Martin Dameris, Nicolas Theys, and Johannes De Leeuw

Abstract. Sulfur dioxide (SO2) is a key atmospheric pollutant, primarily emitted through human activities such as fossil fuel combustion. In atmospheric models, accurate representation of SO2 emission sources, transport, and removal processes are essential for evaluating air quality and radiative forcing.

In this study, we present, for the first time, a comprehensive examination of atmospheric SO2 simulated by the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. First, the tropospheric sulfur budget simulated by EMAC is verified to be close, that is, all sulfur sources and sinks are balanced, ensuring no artificial gain or loss occurs over time due to numerical or conceptual errors. This budget closure is a prerequisite for any further analysis. Second, the results of EMAC simulations are compared with observations from three ground-based networks (the Clean Air Status and Trends Network (CASTnet), the European Monitoring and Evaluation Program (EMEP), and the Acid Deposition Monitoring Network in East Asia (EANET)), mainly over polluted regions, and with vertical column densities retrieved from a TROPOspheric Monitoring Instrument (TROPOMI) on board the Copernicus Sentinel-5 Precursor mission (Sentinel-5P) satellite. The EMAC simulated SO2 concentrations near the Earth’s surface for the year 2019 are, depending on the region, between 1.4 and 1.8 times larger than observed. This discrepancy aligns well with the differences between simulated and retrieved satellite-based measurements of SO2 vertical column densities over the same regions. It indicates that the prescribed SO2 emissions used for the EMAC simulations might be overestimated. Over a longer time period (2000–2019), the EMAC simulation reproduces the measured declining trends of SO2 concentrations and deposited sulfur fluxes in the USA and Europe, but fails to simulate the observed trends in East Asia. This is most likely attributable to the prescribed SO2 emission inventories. Furthermore, sensitivity simulations are performed to assess the emitted amount of SO2 following the Raikoke and Ulawun volcanic eruptions in 2019. The results show a very good agreement of the simulated temporal evolution of the amount of atmospheric SO2 after the eruptions with that retrieved from satellite-based observations.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Geoscientific Model Development.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Ismail Makroum, Patrick Jöckel, Martin Dameris, Nicolas Theys, and Johannes De Leeuw

Status: open (until 31 Oct 2025)

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Ismail Makroum, Patrick Jöckel, Martin Dameris, Nicolas Theys, and Johannes De Leeuw

Data sets

RD1SD: EMAC CCMI-2022 hindcast simulations with specified dynamics, ERA-5, 1979-2019 P. Jöckel et al. https://doi.org/10.26050/WDCC/ESCiMo2_RD1SD

RD1SD: EMAC CCMI-2022 hindcast simulations with specified dynamics, ERA-5, 1979-2019 (additional data) P. Jöckel et al. https://www.wdc-climate.de/ui/entry?acronym=DKRZ_LTA_853_dsg0002

SO2 data of EMAC sensitivity simulations (eruption of Mt. Raikoke, 2019) I. Makroum et al. https://zenodo.org/records/15655676

Ismail Makroum, Patrick Jöckel, Martin Dameris, Nicolas Theys, and Johannes De Leeuw
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Latest update: 05 Sep 2025
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Short summary
We use a state-of-the-art numerical chemistry-climate model to study the atmospheric sulfur dioxide budget. We simulate the atmospheric concentration of sulfur dioxide (SO2) and corresponding sulfur deposition fluxes and compare the results with observational data from a satellite instrument and with ground-based in-situ measurements. For the evaluation of the simulated atmospheric lifetime of SO2, we also simulate the fate of SO2 emitted by two volcanic eruptions that happened in 2019.
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