Future changes in surface ozone over the Mediterranean Basin in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx)

Jaidan, Nizar; El Amraoui, Laaziz; Attié, Jean-Luc; Ricaud, Philippe; Dulac, François

doi:https://doi.org/10.5194/acp-18-9351-2018

Articles | Volume 18, issue 13

https://doi.org/10.5194/acp-18-9351-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

CHemistry and AeRosols Mediterranean EXperiments (ChArMEx)...

https://doi.org/10.5194/acp-18-9351-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 13

Research article

|

04 Jul 2018

Research article |

| 04 Jul 2018

Future changes in surface ozone over the Mediterranean Basin in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx)

Nizar Jaidan, Laaziz El Amraoui, Jean-Luc Attié, Philippe Ricaud, and François Dulac

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Final revised paper (published on 04 Jul 2018)
Preprint (discussion started on 18 Aug 2017)

Interactive discussion

Status: closed

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

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RC1: 'Future changes in surface ozone over the Mediterranean basin in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx)', Anonymous Referee #1, 20 Aug 2017
- AC1: 'Reply to the comments of the reviewer#1', Nizar Jaidan, 04 Jan 2018
RC2: 'Review', Anonymous Referee #2, 05 Sep 2017
- AC2: 'Reply to the comments of the reviewer#2', Nizar Jaidan, 04 Jan 2018

Peer-review completion

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

AR by David Nizar Jaidan on behalf of the Authors (04 Jan 2018)

ED: Referee Nomination & Report Request started (15 Jan 2018) by William Lahoz (deceased)

RR by Anonymous Referee #3 (29 Jan 2018)

RR by Anonymous Referee #2 (05 Feb 2018)

Suggestions for revision or reasons for rejection

Review of Nizar et al. (second submission)

The authors start to address my previous comments. However, like the other reviewer, I still think that this paper needs further work before it is suitable for publication in ACP. One thing the authors should do is improve the readability of the text by doing the following. (i) Reduce the size of the paragraphs (which are very long) – perhaps by splitting them into smaller units. (ii) Look at the english – in particular, there are quite a few typos. (iii) Rewrite the conclusions, so that they are less of a summary of the results, and more of a reflection of the strengths and weaknesses of the models, in this case for studying climate change in the Mediterranean Basin.

The authors should also address the specific comments below.

Specific comments

P. 1

L. 8-10: Maybe I am missing something, but the text suggests the model ensemble mean simulates well the annual cycle of surface ozone, but that a majority of the models overestimate the surface ozone during the period 2000-2010 and for summer. Is this behaviour consistent? Perhaps you need a clarification here and elsewhere in the paper.

L. 15: Where do these increases in CH4 come from?

P. 2

L. 9: Perhaps include references for these sinks.

P. 3

L. 3: I understand from the list of models that not all are climate-chemistry models. Please clarify. The other referee also made this comment.

P. 5

L. 28: A style point: consider not starting a sentence with an acronym.

P. 8

L. 4: Do you need “obviously”? Omit needless words. Same for “in fact” on P. 9, L. 29.

P. 9

L. 6: You mention several studies, but only provide one reference.

L. 12: I am not sure I understand your statement “according to the radiative forcing”. You mean there is a direct relationship between the temperature increases and the different radiative forcings? Please clarify.

P.10

L. 15-19: Quantify the statements made. I suggest you do not use words like “drastically”. Please avoid hyperbolic language. Do this elsewhere in the paper.

P. 11

L. 30+: Quantify the statements made.

P. 12

L. 29: I suggest you use “complicated” rather than “complex”.

P. 13

L. 6-10: Quantify these statements.

L. 14: Perhaps remind the reader of these scenarios and periods.

L. 24-25: What do you mean by increasing chemical terms? Which chemical terms?

P. 14

Section 5: This is too long and it is difficult to see what inferences one can make about the capability of the models to simulate climate change over the Mediterranean basin. There is just one line at the end of this section. The authors should address this.

Fig. 12: This is not quite the same as Fig. 11. Please reword.

Table 3: Identify which are chemistry-climate models and which are chemistry-transport models.

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ED: Reconsider after major revisions (05 Feb 2018) by William Lahoz (deceased)

AR by David Nizar Jaidan on behalf of the Authors (19 Mar 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Mar 2018) by William Lahoz (deceased)

RR by Anonymous Referee #3 (13 Apr 2018)

Suggestions for revision or reasons for rejection

The authors have untaken several efforts to address the previous review comments and I think the paper is improved. Below I have provided some specific comments on the revised manuscript as well as a comment on their response, and some general comments.

COMMENT ON AUTHORS' RESPONSE
1. The authors were not sure about my comment on figure 6 in my previous review, repeated here:

"If you are showing absolute numbers (are you sure you want to do that?), then it would be good to show comparison numbers from (e.g.) a reanalysis product. Climate models are biased for the global mean, so I am sure that they will be so for a smaller region."

What I meant was that the physical climate world normally deals in anomalies, or changes in parameters from a given period. One reason to do this is that the models are biased for the absolute value, but they might get a trend that agrees with the observations. The authors are showing absolute values for temperature, humidity and rainfall, whereas differences to (say) the 1850 time slice value would be more standard practice. If the authors want to keep absolute values, my point was that it would be useful to evaluate the models against (say) a reanalysis product.

Incidentally, given the biases in both the underlying climate and the chemistry, why report absolute ozone concentrations?

2. For Figure 9 the authors are arguing that they should not apply a field significance test. I would strongly argue that it is best practice to do this. The data are presented as a map, and therefore just relying on local significance is insufficient. As mentioned before, I suggest consulting Wilks (2016, BAMS, doi: 10.1175/BAMS-D-15- 00267.1).

GENERAL COMMENTS
1. For consideration by the authors: The authors now cite Schnell et al. (2015) in the context of hourly ozone analysis, but I would still think that this present manuscript would be more widely useful if the hourly ozone results were analyzed. I appreciate that this is a substantial undertaking, and the manuscript could stand as it is with the monthly mean analysis, but I think it would make the manuscript more relevant.

2. I'm sorry if this sounds like nitpicking, but I would re-encourage the authors to revisit the use of paragraphs. There are still paragraphs going over 20-30 lines (e.g., start of Sections 2.2, 3.1, 3.2 etc etc). New point, new paragraph!

SPECIFIC COMMENTS (incl. minor corrections)
P1, L8 (and elsewhere): You say the "behavior of the annual cycle" is good, but I think this is (still) ambiguous. I would say something like "the shape correlates but the values are biased".

P3, L30: UM-CAM and STOC-HadAM3 produce meteorology without interaction with the concentrations of radiatively active species calculated by the chemistry scheme (NOT "without interaction with climate")

P4, L10: "models, however" -> "models; however" or "models. However" (Bad style to use "however" to start a new clause in the middle of the sentence)

P5, L29: I'm not sure about the "IQR for outliers". A sample outside of the central 50% is not generally considered an "outlier". There are several definitions of course, but perhaps you could use something like Tukey's Fences (see here for an introduction: https://en.wikipedia.org/wiki/Outlier)

P7, L34: "Moreover" -> "However" or "But" (since introducing a counterpoint)

P13, L30: Be clear upfront that this is the chemical budget, excluding horizontal and vertical transport.

P14, L7-8: I must have missed this the first time, but there are no strong reasons for basically defining an emergent constraint on the chemical budget changes ("models that are closest to the observations are the ones with increasing chemical terms". You might consider which models include climate-dependent biogenic emissions, which will have a strong impact on future emissions.

Figure 5: Good that there is a color bar, but needs more description of how it was applied. Perhaps put the data in quintiles?

Figure 6 (see also comment above): rainfall is normally reported as mm/day (convertible from what the models output)

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RR by Anonymous Referee #2 (25 Apr 2018)

ED: Publish subject to minor revisions (review by editor) (25 Apr 2018) by William Lahoz (deceased)

AR by David Nizar Jaidan on behalf of the Authors (28 May 2018) Author's response Manuscript

ED: Publish subject to technical corrections (01 Jun 2018) by William Lahoz (deceased)

Please address the following specific comments:

P. 1

L. 8: I suggest “…is similar to the annual cycle of the ozone observations, but…”
L. 14: Introduce NOx, as you do on p.2
L. 16: I suggest “…the benefits from the reduction…”

P. 2

L. 2: Assessments of what? Chemical and dynamical processes in the atmosphere?
L. 5: “…of the residual…”
L. 21: What exactly do you mean by “hot-spot”?
L. 25: precursor
L. 26: changes. Changes owing to what?
L. 29: I suggest the form “…, e.g., …”
L. 32: The assessment -> An assessment
L. 34: “At the regional scale…”

P. 3

L. 4: Omit “the”
L. 7: “…emissions, and meteorological…”
L. 11 and elsewhere: I suggest you do not start a sentence with an acronym
L. 13-14: Perhaps it would be better to write. “…and analyses the driving forces…”
L. 18: changes
L. 19: these changes
L. 26+: Introduce acronyms for the models when first used

P. 4

L. 17: “…according to the radiative…”
L. 24: I suggest “…), and one very…”
L. 27: Secondly -> Second. To match the use of “first” earlier

P. 5

L. 14: I suggest you use “one” and “four” instead of “1” and “4”

P. 6

L. 6: “…from a local…”
L. 25: Is the bias positive? If so, indicate

P. 7

L. 13: For multiple citations order the citations by alphabetical or chronological order but do not mix. In particular, for citations in the same year, order alphabetically
L. 23: Introduce the acronym for “sd” – you do so in P. 13

P. 8

L. 27: Do you really mean global scales? Earlier, you suggest you focus on the Mediterranean Basin. Please clarify

P. 9

L. 5: “…that the CMAM…”
L. 8: Perhaps better to write “…bias is positive at the regional and global scales for all models except…” Is this what you mean?
L. 10: “…in the recent past…”
L. 15: “…and future…”

P. 10

L. 26: “…The CH4…” I suggest you do not start sentences with an abbreviation or acronym

P. 11

L. 2: “Tukey’s fences rule…” Omit “the”

P. 12

L. 7: bias -> biased
L. 16: I suggest you mention first the earlier year, e.g., “2000 (REF) and 2030”

P. 13

L. 4: “…due to evaporation…”
L. 23: showed -> show

P. 14

L. 18: has -> have
L. 20: “…is similar in magnitude for the two scenarios…”
L. 26: Quantify the “intense” mentioned. “Latter” what?

P. 15

L. 9: “…combined with a…”
L. 28: “For the 2030…”

P.16

L. 4: Could you quantify this proportional behaviour?
L. 7: You mean that the net effect is one of randomness. Clarify

P. 17

L. 22: You suggest these other results are significant. If so, at which level?
L. 23-24: Quantify the “intensively” and “less strongly” qualifications
L. 26+ paragraph: Quantify the decreases mentioned
L. 31: I suggest you avoid the use of “etc”

P. 18

L. 3-4: Indicate how this builds on the work done in this paper.
L. 8: improve -> improved

P. 26

Fig. 2: thin line -> thin lines. Mention in the caption the legends in the two figures

P. 30

Fig, 6: Please rephrase the penultimate sentence; it is not clear to me

P. 33

Fig. 9: When talking about the anomalies, I suggest you mention first the earlier year, e.g., “2030-2100”

P. 35

Fig. 11: “…the multi-model mean…”; “…by the whisker…”. Same for Fig. 12.

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AR by David Nizar Jaidan on behalf of the Authors (09 Jun 2018) Author's response Manuscript

Short summary

The Mediterranean Basin, surrounded by three continents with diverse pollution sources, is particularly sensitive to climate change due to its location and diversity of ecosystems. In this work, we investigate the future change of surface ozone from 2000 to 2100 over this region using a set of atmospheric model outputs and ground-based observations. We also highlight how the future climate change and the increase of methane concentrations can offset the benefit of the pollution reduction policy.