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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 May 2020

Submitted as: research article | 20 May 2020

Review status
This preprint is currently under review for the journal ACP.

Attribution of ground-level ozone to anthropogenic and natural sources of NOx and reactive carbon in a global chemical transport model

Tim Butler1,2, Aurelia Lupascu1, and Aditya Nalam1,2 Tim Butler et al.
  • 1Institute for Advanced Sustainability Studies, Potsdam, Germany
  • 2Institut für Meteorologie, Freie Universität Berlin, Germany

Abstract. We perform a source attribution for tropospheric and ground-level ozone using a novel technique which accounts separately for the contributions of the two chemically distinct emitted precursors (reactive carbon and oxides of nitrogen) to the chemical production of ozone in the troposphere. By tagging anthropogenic emissions of these precursors according to the geographical region from which they are emitted, we determine source/receptor relationships for ground-level ozone. Our methodology reproduces earlier results obtained through other techniques for ozone source attribution, and also delivers additional information about the modelled processes responsible for intercontinental transport of ozone, which is especially strong during the spring months. The current generation of chemical transport models used to support international negotiations aimed at reducing the intercontinental transport of ozone show especially strong inter-model differences in simulated springtime ozone. Current models also simulate a large range of different responses of surface ozone to methane, one of the major precursors of ground-level ozone. Using our novel source attribution technique, we show that emissions of NOx from international shipping over the high seas play a disproportionately strong role in our model system to the hemispheric-scale response of surface ozone to changes in methane, as well as to the springtime maximum in intercontinental transport of ozone and its precursors. We recommend a renewed focus on improvement of the representation of the chemistry of ship NOx emissions in current-generation models. We demonstrate the utility of ozone source attribution as a powerful model diagnostic tool, and recommend that similar source attribution techniques become a standard part of future model inter-comparison studies.

Tim Butler et al.

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Tim Butler et al.

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Publications Copernicus
Short summary
Ground-level ozone is not directly emitted, but rather formed chemically in the atmosphere. Some ground-level ozone is transported from the stratosphere, but most is produced from reactive precursors which are emitted by both natural and man-made sources. We present the results of a novel source apportionment method for ground-level ozone. Our results are consistent with previous work, while also providing new insights. In particular we highlight the role of methane and international shipping.
Ground-level ozone is not directly emitted, but rather formed chemically in the atmosphere. Some...