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- Title
Revisiting the contribution of land transport and shipping emissions to tropospheric ozone.
- Authors
Mertens, Mariano; Grewe, Volker; Rieger, Vanessa S.; Jöckel, Patrick
- Abstract
We quantify the contribution of land transport and shipping emissions to tropospheric ozone for the first time with a chemistry-climate model including an advanced tagging method, which considers not only the emissions of NOx (NO and NO2), CO or non-methane hydrocarbons (NMHC) separately but the competing effects of all relevant ozone precursors. For summer conditions a contribution of land transport emissions to ground level ozone of up to 18% in North America and South Europe is estimated, which corresponds to 12 nmol mol-1 and 10 nmol mol-1, respectively. The simulation results indicate a contribution of shipping emissions to ground level ozone during summer in the order of up to 30% in the Northern Pacific (up to 12 nmol mol-1) and 20% in the Northern Atlantic (12 nmol mol-1). To put these estimates in the context of literature values, we review previous studies. Most of them used the perturbation approach, in which the results from two simulations, one with all emissions and one with changed emissions for the source of interest, are compared. The comparison shows that the results strongly depend on the chosen methodology (tagging or perturbation method) and on the strength of the perturbation. A more in-depth analysis for the land transport emissions reveals that the two approaches give different results particularly in regions with large emissions (up to a factor of four for Europe). With respect to the contribution of land transport and ship traffic emissions to the tropospheric ozone burden we quantified values of 8% and 6% for the land transport and shipping emissions, respectively. Overall, the emissions from land transport contribute to around 20% of the net ozone production near the source regions, while shipping emissions contribute up to 52% to the net ozone production in the Northern Pacific. Our estimates of the radiative ozone forcing due to emissions of land transport and shipping emissions are 92 mW m-2 and 62 mW m-2, respectively. Again these results are larger by a factor of 2-3 compared to previous studies using the perturbation approach, but largely agree with previous studies which investigated the difference between the tagging and the perturbation method. Overall our results highlight the importance of differing between the perturbation and the tagging approach, as they answer two different questions. We argue that only the tagging approach can estimate the contribution of emissions, while only the perturbation approach investigates the effect of an emission change. To effectively asses mitigation options both approaches should be combined.
- Subjects
TROPOSPHERIC ozone; EMISSIONS (Air pollution); MARITIME shipping &; the environment; TROPOSPHERE; ECOLOGICAL disturbances
- Publication
Atmospheric Chemistry & Physics Discussions, 2017, p1
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acp-2017-747