Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative

Lamy, Kévin; Portafaix, Thierry; Josse, Béatrice; Brogniez, Colette; Godin-Beekmann, Sophie; Bencherif, Hassan; Revell, Laura; Akiyoshi, Hideharu; Bekki, Slimane; Hegglin, Michaela I.; Jöckel, Patrick; Kirner, Oliver; Liley, Ben; Marecal, Virginie; Morgenstern, Olaf; Stenke, Andrea; Zeng, Guang; Abraham, N. Luke; Archibald, Alexander T.; Butchart, Neil; Chipperfield, Martyn P.; Di Genova, Glauco; Deushi, Makoto; Dhomse, Sandip S.; Hu, Rong-Ming; Kinnison, Douglas; Kotkamp, Michael; McKenzie, Richard; Michou, Martine; O'Connor, Fiona M.; Oman, Luke D.; Pitari, Giovanni; Plummer, David A.; Pyle, John A.; Rozanov, Eugene; Saint-Martin, David; Sudo, Kengo; Tanaka, Taichu Y.; Visioni, Daniele; Yoshida, Kohei

doi:https://doi.org/10.5194/acp-19-10087-2019

Articles | Volume 19, issue 15

https://doi.org/10.5194/acp-19-10087-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Chemistry–Climate Modelling Initiative (CCMI) (ACP/AMT/ESSD/GMD...

https://doi.org/10.5194/acp-19-10087-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 15

Research article

|

12 Aug 2019

Research article |

| 12 Aug 2019

Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative

Kévin Lamy, Thierry Portafaix, Béatrice Josse, Colette Brogniez, Sophie Godin-Beekmann, Hassan Bencherif, Laura Revell, Hideharu Akiyoshi, Slimane Bekki, Michaela I. Hegglin, Patrick Jöckel, Oliver Kirner, Ben Liley, Virginie Marecal, Olaf Morgenstern, Andrea Stenke, Guang Zeng, N. Luke Abraham, Alexander T. Archibald, Neil Butchart, Martyn P. Chipperfield, Glauco Di Genova, Makoto Deushi, Sandip S. Dhomse, Rong-Ming Hu, Douglas Kinnison, Michael Kotkamp, Richard McKenzie, Martine Michou, Fiona M. O'Connor, Luke D. Oman, Giovanni Pitari, David A. Plummer, John A. Pyle, Eugene Rozanov, David Saint-Martin, Kengo Sudo, Taichu Y. Tanaka, Daniele Visioni, and Kohei Yoshida

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Final revised paper (published on 12 Aug 2019)
Preprint (discussion started on 11 Jun 2018)

Interactive discussion

Status: closed

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

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RC1: 'Comments to authors', Anonymous Referee #1, 02 Jul 2018
- AC1: 'Response to referee 1', Kevin LAMY, 17 Sep 2018
RC2: 'Reviewer comments', Anonymous Referee #2, 03 Jul 2018
- AC2: 'Response to referee 2', Kevin LAMY, 17 Sep 2018

Peer-review completion

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

AR by Kevin LAMY on behalf of the Authors (18 Sep 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Sep 2018) by Paul Young

RR by Anonymous Referee #1 (28 Sep 2018)

Suggestions for revision or reasons for rejection

The authors have responded to my queries, but in some cases the response is not quite correct and needs further revision (see below). The paper is difficult to follow – in many parts the language is in poor English, there are some very long sentences, and some sentences that seem to be out of place. The simulations need to be better described – I could not find anywhere what the various bits of senC2rep26 stood for – 26, presumably RCP 2.6. The simulations need to be listed and explained in one of the tables. UV is inconsistently used as UV, UVR, UV radiation – it should be consistent. Also, on page 6 TSO2 is defined then, TSO2 used.

Specific comments:
Introduction
1. Page 3, Line 8. Sentence starting “Overexposure” should be a new para. This section on health risks is not quite right – and the detail given about the exposures is not necessary (and ‘due to sunburns during childhood years’ is not correct – there is an increased risk associated with sunburns during childhood years, but sunburn and higher sun exposure at all ages are important to melanoma risk). I would suggest replacing lines 8-14 with the following: “Exposure to UV radiation has both adverse and beneficial effects on human health. Overexposure increases the risk of skin cancers, e.g. cutaneous malignant melanoma and keratinocyte cancers, and a range of eye diseases. Underexpsoure increases the risk of vitamin D deficiency; vitamin D is critical to healthy bones. It is common in health research and public health messaging to use the UV Index (UVI) as a measure of erythemally (sunburn) weighted UV irradiance.”
2. Page 3. The sentence starting “Dhomse et al” on line 22 seems to be an add-on that is not in the correct place.
3. Page 3, Line 33: why is it “Consequently” – this seems to be the wrong word, since the rest of the sentence does not seem to relate to the sentences that precede it.
4. Page 4, Line 1 – stratospheric ozone absorbs UV-B radiation (not UV)
5. Page 4. Typographical error line 6 – ‘scaterring’
6. Page 4. Line 19 – this is a very long sentence with a large number of acronyms, it is very difficult to read.
7. Page 5: the information about RCPs could probably go in the Introduction.

Data and methodology
1. The A1 scenario is not explained
2. The simulations are not explained (see general comments). I don’t think it is enough to say they are described in a different paper. In addition, this last paragraph on page 5 seems very disordered. It is difficult to follow.
3. Page 6: line 5-7. This is already in the list on page 5. Could be deleted in one location.
4. Page 6, line 28 – two sensitivity simulations – is this C2fODS & C2Fghg? If you call these sensitivity simulations at the first mention, this will be clearer to the reader.

Model validation
1. Page 8, lines 21-28 – is this relevant to include here, or better placed in the Discussion?
2. Page 9. There is no need for a paragraph break at line 3. Put the two paras together.
3. Please explain ‘the global relative difference of the monthly difference” a bit further (maybe an equation would be useful to clarify this)

4.3 Effects of greenhouse gases
1. Page 12: “these are simulations based on refC2…” this has already been noted earlier and should be deleted here.
2. Page 12, last line. Change “decent increase” to a “moderate increase” – something more scientific than ‘decent’
4.4 Other effects affecting UVI (note the typo in the heading – Others effects)
1. Page 13. Sentence at line 18-19 seems to be out of place.

Conclusion
1. This seems quite well written and provides a nice summary of the results – although it is more a summary of the results than a conclusion.
2. Page 15, line 7-8. Not clear what this sentence means: ‘This study focused on UVI which does not directly impact human health’. UVI is erythemally weighted UV irradiance – so is weighted for a human health effect. The following sentence about further investigation is very naïve and should be deleted – behaviour is a very important moderator of any link between UV irradiance and human health impact. It would be impossible just to change UV irradiance and look for human health impacts, without taking a lot of other parameters into account. Maybe best just to say it is complicated by human behaviour and not recommend further investigations.

Tables
1. Table 2 needs a much better description of what it is showing.

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RR by Anonymous Referee #2 (07 Oct 2018)

Suggestions for revision or reasons for rejection

General comments:

The revised manuscript has been improved but there are still weaknesses that must be taken into consideration before it is accepted for publication. See specific comments below.

The language of the manuscript needs further attention, as well as the flow of the text in some cases. Apart from the corrections suggested in the first review, there has been no attempt to improve it. I am sure that one of the co-authors could help in this context.

Specific Comments:

These are separated into two categories: First I list my previous comments (in parentheses) which, to my opinion, have not been addressed properly.

(General Comment). I still believe that the use of average ozone columns in RTD simulations does not allow assessing the uncertainty of the presented UVI simulations. I understand however, that repeating the calculations is not possible at this stage of the study.

Comment (4): P6, L6: The authors’ response in my comment on the spectral characteristics of the albedo used in the UV calculations has not been reflected in the text. Please add.

Comment (8): P6, L24: Another case of responding to a comment without passing the explanation in the text. Please explain for the sake of the readers, why using zonally averaged ozone and temperature profiles does not introduce important uncertainties.

Comment (14) was not taken into account, nor was a response from the authors. See below:
P7, L32- P8, L10: Please check this section and make the discussion clearer. I suggest focusing the discussion on differences between model and GB data and not on differences between GB and OMI because this is not the main subject of this paper. The changes reported in the abstract and the conclusions (-4 to 11%) are not discussed at all in this section. Furthermore it would be good to report in Table 3 the spread of the model differences to GB for each station (e.g. the standard deviation).

Comment (15): I haven’t identified in the text any “Specifications on the averaging process and on the limitation of this sensitivity analyses have been added.”, as quoted by the authors.

Comment (18): I insist on my previous comment that you cannot compare changes between two studies that are based on different periods, without mentioning that explicitly in the text. If you see Figure 3 of the Dhomse 2018 paper, it is obvious that total ozone was much higher in 1960 than in 1980 almost everywhere except in the tropics. Taking these differences into consideration you could estimate the additional change in UVI that is induced by the ozone difference. For example, in SH midlatitudes ozone is about 2.5% higher in 1960 meaning that UVI would be at least 3% lower in 1960 than in 1980. This change is comparable to the changes that Bais 2011 and the present study have reported.

Comment (21): The first sentence of the conclusions should indicate how good the UVI is reproduced by the model. Here is a suggestion: “We have shown that the use of CCMI model data with a radiative transfer model (TUV) can reproduce the current climatological values of clear-sky UVI derived from measurements, in most cases, to within ±5%.” This is my take on message from the results of Table 3.

New comments:

P4, L8: (Mayer et al., 1998) is not a good reference for cloud enhancement. This paper discusses the apparent large increases of total ozone under optically thick clouds. Possible alternatives:
Marín et al., 2017, http://dx.doi.org/10.1016/j.atmosres.2017.05.008
Lovengreen et al., 2005, https://doi.org/10.1029/2004JD005372

P8, L9-10: It is now clear what you mean with “Here, a similar conclusion can be drawn,…”. What is the compulsion and to what it refers? The previous conclusion was about OMI being higher than GB observations. Please revise the text. Moreover, an overestimation of 10% was found for Palmer but there is not discussion on what could cause this discrepancy.

P8, L15: The altitude effect of UVI is the order of 7-8% increase per km altitude (McKenzie et al., 2001). This means that, for Mauna Loa, the relative difference between modeled for sea-level and measured UVI should be at least -25% while in Table 3 the difference is about 5% and of opposite sign. In Figure 1 both the median and mean based model results are higher than the measurements with one exception in June where the difference is in the right direction but much smaller than it should be. Therefore, the statement in line 17: “Nonetheless, at low and mid-latitudes the UVI differences observed are fully compatible... “, is invalid, and of course the comparison is not good for unidentified reasons.

P9, L5: The newly added sentence refers to latitudinal differences, but these are already taken into account in Figure 3. Consider revising to: “Due to seasonal and inter-model differences, this approach has limitations…”

P14, L11-12: These sentences belong to the introduction (already referenced). They are not conclusions of this paper, and as they are written create some confusion as to what means “reproduced” UVI.

P14, L23: According to Fig. 4, UVI does not return to 1960 levels at high southern latitudes when TOZ returns. It stays 5-8% above except for RCP 8.5 when TOZ exceed the 1960 levels. Please rephrase.

P14, L27: The statement: “In mid-latitudes, TOZ should increase between 1960 and 2100 in both hemispheres for all RCPs except RCP 8.5.”, is not correct: a) TOZ must be replaced with UVI. b) UVI increases between 1980 (not 1960) and 2100 only in the NH midlatitudes. In the SH midlatitudes the pattern is completely different, as it appears from Figure.

P15, L3-5: Please state to which time frame refers the quoted variability 0-3%. Surprisingly, in the next sentence the variability reaches 10%, without saying to which latitude or period it refers. Please clarify.
Table 3 caption: In the last line it is stated “For Barrow and Palmer station we selected the six months of their respective summer.” Since summer has only 3 months. It is better to explicitly name the months that were used.

Technical:
Note: These are only a few examples of language and appearance issues.

P2, L12: I suggest rephrasing to: “Higher increases in UV index are projected …”

P2, L19: I suggest rephrasing to: “…of ozone to 1960 values, with a corresponding pattern of change observed on UVI, …”

P7, L7-8: As there is no other second-level heading, heading “3.1 Model Validation” should be deleted. I suggest to stop heading 3 at the colon to become: “3 Model Validation”.

P14, L14: Replace “ranges” with “ranging”

P15, L4: The word “Logically” does not make sense. Please remove. Also, replace “hemisphere;” with “hemispheres”

Figure 4: I suggest to maintain consistency in the vertical axes labels; some of them are drawn with one decimal, some without. Include a note in the caption, that the scale of the vertical axes is not the same for all panels. Same for Figure 6.

Caption Figure 6: The last sentence has been copied form Figure 4. But this figure does not show the four RCPs, but the three experiments. Please correct.

Caption Figure 8: The word “modelized” does not exist in English. Please replace with modelled (three occurrences). Please change also “from 2000-2010 values” to “from 2000 to 2010“. Same for Figure 9.

Axes titles in Figures 4,6,8,9: Remove the word “percent” since there is already a [%] sign.

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ED: Reconsider after major revisions (21 Oct 2018) by Paul Young

AR by Kevin LAMY on behalf of the Authors (30 Dec 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (28 Jan 2019) by Paul Young

RR by Anonymous Referee #2 (05 Feb 2019)

Suggestions for revision or reasons for rejection

The paper has certainly been improved. My few comments below (except the second) are mainly minor aiming at improving the readability of the paper. As long as the 2nd comment is taken into account I would have no objections to recommend publication of the manuscript.

1. As cloud effects in UV radiation are not considered, I suggest changing the title to: “Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative”

2. In the model validation (section 3) I have still some concerns about the comparisons for Mauna Loa. The authors try to explain the differences of about 5±9% between modeled and measured values of the UVI, but they do not realize that they should try to explain why the differences are not -25%. As explained in my review (3rd new comment), due to the altitude of the site, the measured UVI should be at least 25% higher than the modeled value that refers to sea-level. In Table 4 the modeled value is higher by 5%, which makes a difference or about 30%. I think that something is wrong with the data used for Mauna Loa. A recent poster presentation by the data providers shows that the noon UVI should be between 15 and 16 while in Figure 1 the data are between 11 and 14. Similarly the minimum values should be about 8 and not 5-6 as in Figure 1. I suggest checking the data that were used. It might be that the averages are from all data and not only cloud-free as reported in the paper. If this is the case, then the comparisons are invalid and this should be explicitly stated in the paper.

3. I haven’t seen any acknowledgments to the data provides of the stations used in this study. As, I am not fully aware of the data policy of NDACC, I am just warning the authors to check if there is any special requests for this.

4. I have spotted the following typographical and grammatical defects. I mainly provide the correct form of the words, unless otherwise specified.

6, 4: “summary”
7, 19: “by spectroradiometers”
7, 19: “from the spectral irradiance measurements.”
8, 16-17: ”they range” (2 occasions)
8, 23: “UVI units”
8, 27: Capitalize September December
8, 31: “stations”
8, 32: “varies”, “patterns”
8, 34: “the differences between Mauna Loa and Palmer stations”, delete “a” (part of…)
9, 6: change “estimate” to “verify”
10, 16: “drive”
10, 24: “this will be verified” to “as discussed”
10, 30: “changes”
11,1: “UVI is almost constant, due to effects of AOD changes (see section 4.4).”
13, 22: “we found an UVI” “we discussed UVI”
13, 29: 6% change in UVI in 2100
14, 5: “clear-sky UV levels”
14, 6: Delete “percent” (2 occasions)
15, 2: “account for” to “explain”
15, 6: ”cloud effects”
15, 8: “TOZ returns”
15, 10: “will arrive” to “will occur”
15, 14: “there are months”
15, 18: “of clear-sky UV variability”
15, 19-20: “are considered to be evolving” to “vary”
15, 29: Delete “percent”
15, 33: “numerous” to “several”
16, 1: “precisely “ to “ more accurately”

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RR by Anonymous Referee #1 (08 Feb 2019)

Suggestions for revision or reasons for rejection

Some issues in the paper have been fixed, but there remain a number of issues with incorrect and inconsistent language and punctuation (including some that the author response would suggest had been fixed). Poor structure of some of the main results paragraphs make for very confusing reading.

Specific comments
1.
1. Page3, Line 2: specify “stratospheric ozone layer”
2. Page3, Line 13: UV radiation also impacts the biosphere (missing word)
3. Page3, Line 23: “future surface UV radiation”
4. Page 3, line 33: affecting surface levels of UV radiation (also line 34 and a number of other places in the manuscript – please find and replace where necessary)
5. Page 4, line 2 – should this be ‘larger SZA” rather than ‘higher’?
6. Page 4, line 13 – CCMI not yet defined (is defined further down in line 18)
7. Page 4, line 29 – bracket missing before (Meinshausen et al)
8. Page 5 heading – should this be “Modelling UV irradiance”?
9. Page 5, line 5 – is ‘integrated” the correct word? UVI is also irradiance, so it is not clear what integration is performed to get from irradiance to UVI
10. Page 6, line 4: “summary” rather than “summaries”
11. Page 6, line 13: rephrase “eventually local erroneous values”
12. Page 8: line 27: missing capitals on Sept and Dec
13. Inconsistent capitalisation of Northern and Southern Hemisphere
14. Page 9, line 13: suggest add “While we recognise that this is not the best approach…”
15. Page 9, line 18: delete ‘one’
16. Page 9, line 30 – this has already been said on page 6, line 24. Remove the repetition.
17. Page 10, line 33: “In the Northern Hemisphere…” – which latitude band is this referring to?
18. Page 10-11 – last para page 10 and continued as first para page 11. This paragraph jumps back and forth between north and south latitudes, and between different latitude bands – this makes it very hard to follow. It should be revised with a better structure. (the same lack of structure is apparent in the next two paragraphs, and needs revision).
19. Page 14, line 25 “climatological” – spelt incorrectly.
20. Page 14, line 31. Sentence starting “While the mean…” is not a sentence – needs to be rephrased.
21. Page 15, para starting on line 12. This is very confusing: “UVI changes in this region are not homogeneous; (not clear what ‘region’ is meant, but perhaps mid-latitudes as at the beginning of the para). But next part of the sentence discusses southern hemisphere 20°-30° - which by the definition in the paper is low latitude/tropics.
22. Titles for tables 2 and 3 are not in the correct order
23. Relative difference definition is this 100*? (under several tables and figures). Below Figure 3, RD for UVI is defined as 200* - is this correct?
24. Figure 4 legend – the latitude bands are described nicely in the legend, but the abbreviation used on the figure should be added, e.g. Northern Tropical Band (TN, 0-30 N) etc (similarly for Figure 6)

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ED: Reconsider after major revisions (22 Feb 2019) by Paul Young

AR by Kevin LAMY on behalf of the Authors (17 May 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Jun 2019) by Paul Young

RR by Anonymous Referee #2 (14 Jun 2019)

ED: Publish subject to technical corrections (26 Jun 2019) by Paul Young

AR by Kevin LAMY on behalf of the Authors (04 Jul 2019) Author's response Manuscript

Short summary

In this study, we simulate the ultraviolet radiation evolution during the 21st century on Earth's surface using the output from several numerical models which participated in the Chemistry-Climate Model Initiative. We present four possible futures which depend on greenhouse gases emissions. The role of ozone-depleting substances, greenhouse gases and aerosols are investigated. Our results emphasize the important role of aerosols for future ultraviolet radiation in the Northern Hemisphere.