Attributing ozone and its precursors to land transport emissions in Europe and Germany

Mertens, Mariano; Kerkweg, Astrid; Grewe, Volker; Jöckel, Patrick; Sausen, Robert

doi:https://doi.org/10.5194/acp-20-7843-2020

Articles | Volume 20, issue 13

https://doi.org/10.5194/acp-20-7843-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

The Modular Earth Submodel System (MESSy) (ACP/GMD inter-journal...

https://doi.org/10.5194/acp-20-7843-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 13

Research article

|

06 Jul 2020

Research article |

| 06 Jul 2020

Attributing ozone and its precursors to land transport emissions in Europe and Germany

Mariano Mertens, Astrid Kerkweg, Volker Grewe, Patrick Jöckel, and Robert Sausen

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Final revised paper (published on 06 Jul 2020)
Supplement to the final revised paper
Preprint (discussion started on 13 Sep 2019)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of acp-2019-715', Anonymous Referee #1, 08 Nov 2019
- AC1: 'Reply', Mariano Mertens, 15 Feb 2020
RC2: 'Review', Anonymous Referee #2, 13 Nov 2019
- AC2: 'Reply', Mariano Mertens, 15 Feb 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Mariano Mertens on behalf of the Authors (24 Feb 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Feb 2020) by Andreas Hofzumahaus

RR by Anonymous Referee #2 (03 Mar 2020)

RR by Anonymous Referee #1 (16 Mar 2020)

Suggestions for revision or reasons for rejection

This revised version of the paper has been very much improved although the English should yet be reviewed. In this respect, I listed again some possible improvements (see the minor comment section) but the whole text would need to be revised. I remain with one major question / concern that has not been answered by the Authors and I would appreciate some answers before I could recommend publication.

The major concern / question I would like to come back to is a point I raised in my first review. I believe it was not answered satisfactorily. I agree with the Authors that sensitivity analysis and tagging are two approaches that are used to answer diﬀerent questions. I also agree that on one hand, sensitivity delivers impacts that are used to answer the policy question: “what is the potential eﬀect of an emission reduction on air quality levels?” And on the other hand, tagging delivers contributions. But I yet do not understand to what policy or science question contributions answer. How should we use contributions? For what purpose? For example, the Authors state that their goal is to quantify contributions and that tagging is well suited to do this. I agree with this statement but what for? They also state that contributions are the ﬁrst step in understanding the inﬂuence of diﬀerent emission sources. But both impacts and contributions would serve that purpose. What is the added value of contributions to understand the influence of emission sources?
As the entire work is devoted to the analysis and quantification of contributions, some information should be provided to clarify these points.

Minor comments

1) P25 L3-4 The Authors state that “land transport contributions increase with higher ozone values, hence land transport emissions are an important driver of large ozone values”. In my view we would get the same interpretation with low ozone values. In the extreme case of ozone titration, large transport contributions would increase with lower ozone values. Could the Authors comment on this?
2) What are the exact differences between sections 4 and 6? The section titles look very similar but the approaches followed in each section differs. I would suggest adding a few lines to clarify this.
3) P31 L6-8: “Stating that the contributions to ozone are more robust, i.e. less dependent on the background than impacts”. I think this statement is confusing. The real world shows variations with respect to the background but contributions do not. Contributions are indeed more robust but they do not represent the real world. Could the Authors comment on this?
4) P2 L28-29: In practice, the sensitivity or perturbation method is not restricted to small perturbations around the base case. Larger perturbations can be applied while keeping linear responses but this strongly depends on the time average selected and on the pollutant considered. For annual averages, reductions up to 50% have been tested and the model responses remain linear for PM but also for O3 (see e.g. Thunis et al. 2015). Obviously this is not the case for episodes, but even then reductions up to 20% can be applied. I would therefore adapt the text in the introduction to mention these points.

P3 L2: This sentence is rather unclear as it seems to mix the concept of contributions with impacts.
P3 L28/29: The sentence is grammatically incorrect and unclear. Please revise English
P4 L9: trough --> through but I would suggest inserting this point: “choice of source…” as an independent points
P5 L 31: an one --> a one
P7 L 21: As discussed…
P8 L8-14: Again here, the Authors seem to mix the impact and contribution concepts (especially L8 and 9). Please clarify
P9 L5: as the --> than the
P9 L15/16: The sentence is grammatically incorrect and unclear. Please revise English
P9 L25: sectors anthropogenic non-traffic --> anthropogenic non-traffic sectors
P10 L 4: and the emission differences between both simulations
P10 L14: simulations
P11 L3: too less --> too low
P12 L10: The sentence is grammatically incorrect and unclear. Please revise English
P13 L4: at the European scale
P13 L17: to the share…
P14 L1: these differences between contributions…
P18 L3: ground level ozone
P18 L4: non-traffic is quite unclear: could we say what it is rather than what it is not?
P18 L18: DJF ground level O3
P18 L19: absolute --> real and these contributions --> contributions reported in this work?
P19 L11/L2: The sentence is unclear. Please revise
P24 L6 & 8: percentiles
P24 L17: representations
P24 L33 Please revise and clarify sentence
P28 L 11: differences of the --> differences between
P28 L12-14: The sentence is unclear. Please revise
P30 L27-28: This also depends on the availability of VOC
P31 L11-12: The wording “sensitivity approach” in this sentence is misleading as this is the same term used to differentiate impacts and perturbations.
P32 L2: their approach
P32 L14: The sentence is grammatically incorrect and unclear. Please revise English
P32 L18: between the two emission…
P32 L31: by up to
P33 L12-13: The sentence is grammatically incorrect and unclear. Please revise English

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ED: Reconsider after major revisions (16 Mar 2020) by Andreas Hofzumahaus

AR by Mariano Mertens on behalf of the Authors (27 Apr 2020) Author's response Manuscript

ED: Publish as is (11 May 2020) by Andreas Hofzumahaus

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Short summary

We investigate the contribution of land transport emissions to ozone and ozone precursors in Europe and Germany. Our results show that land transport emissions are one of the most important contributors to reactive nitrogen in Europe. The contribution to ozone is in the range of 8 % to 16 % and varies strongly for different seasons. The hots-pots with the largest ozone concentrations are the Po Valley, while the largest concentration to reactive nitrogen is located mainly in western Europe.