the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Jun 2026
The impact of the Hunga eruption on the 2023 Antarctic ozone hole: contrasting effects in the core and edge regions of the polar vortex
Abstract. The January 2022 Hunga eruption injected an exceptional 150 Tg of water vapour (H2O) into the stratosphere causing an enhancement not observed previously within the satellite era, with extensive and ongoing effects. From global chemical transport model simulations, we further assess the high-latitude H2O enhancement caused by the eruption, and how it influenced the 2023 Antarctic ozone depletion across two vortex regimes: the cold core and the less cold, and more insolated vortex edge region. Our simulations show the H2O chemical impacts arose mainly from the H2O enhancement promoting earlier formation of polar stratospheric clouds (PSCs), which in turn enhanced chlorine activation and subsequent ozone loss. We also show ice PSC dehydration in the vortex core limited Hunga’s chemical effects to occur for only the first 25 % of the vortex season; consequently, the edge region experienced the largest chemical impact to ozone depletion in 2023. Overall, the H2O enhancement increased Antarctic ozone hole area by 7 % but remaining within the historical variability over the past two decades. Sensitivity simulations including the Hunga sulfate aerosol show H2O-driven heterogeneous chlorine activation on additional PSCs, dominated the chemical impacts of Hunga on polar ozone, with only minor impact from activation on volcanic sulfate aerosol. Our results highlight that while water-rich large volcanic eruptions can worsen polar ozone depletion, the magnitude of the impact is strongly influenced by stratospheric temperatures through dehydration. This suggests that less cold vortex environments, e.g. the Arctic, may experience larger relative changes in chlorine activation under similar conditions.
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Status: final response (author comments only)
- CC1: 'Community Comment on egusphere-2026-3619', Farahnaz Khosrawi, 12 Aug 2026
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RC1: 'Comment on egusphere-2026-3619', Anonymous Referee #1, 27 Aug 2026
The authors use model simulations to assess the influence of additional stratospheric water vapor and sulfate from the Hunga volcanic eruption on the 2023 Antarctic ozone hole. The colder core region and less cold edge vortex region are evaluated separately.
The topics covered are important and within the scope of ACP. This is not a transformative study, but the results have value and the analyses appear to have been carefully done. I support publication of this manuscript after addressing some concerns:
(1) The naming of the Simulations and Experiments in Table 1 and 2 are not at all intuitive, and it makes following the analyses in the paper significantly harder than it needs to be. Control_G, Clean, and Clean_H2O are essentially meaningless names. The simulations in Table 1 should be renamed so that the names are descriptive and clearly represent the perturbations that were done:
Control_G rename to: Aerosol only
Hunga_H2O rename to: H2O+Aerosol (or Combined)
Clean rename to: Background
Clean_H2O rename to: H2O only
I certainly would not insist that the authors use my exact suggestions if they have alternate ideas, but I do not support publication of this paper until the simulation names are changed to something more descriptive and intuitive than what they currently are.
The experiment labels in Table 2 are an additional naming complexity that is not necessary and makes the simple comparisons in the paper harder to follow. When simulations are subtracted from one another, the equation should be written out at each point in the manuscript (and actually almost always is in the current draft), so having a separate Table 2 defining “experiments” with ambiguous “Experiment labels” is not necessary and makes the paper less clear. I recommend deleting Table 2 and all mentions of the Experiment labels in the paper.
(2) Much of the paper is presented such that the reader is repeatedly asked to eyeball the colors in two similar figure panels, while the text qualitatively describes them in detail. I suggest that the authors consider making difference plots (e.g., Fig 3e minus Fig 3g, and others) as additional panels in the figures, which would make the differences immediately obvious and allow for a more quantitative approach and hopefully a more concise text description.
(3) The text is longer than necessary in many places. It would be ideal to have the text descriptions of the figures be more succinct, focus on the key points, and move the extra detail to supplemental. The paper has simple takeaway points and appears to be significantly longer than necessary.
Additional Comments/Corrections:
There are a good number of typos throughout. Please carefully go through it.
Line 9. Be clear whether this 7% result is from the model or measurements. Change ‘remaining’ to ‘remained’
Lines 17-18 and throughout. Use consistent date formats.
Line 22. Add ‘approximately’ before ‘150’.
Lines 74-75. Be more explicit regarding the wildfire impacts. Is it ‘including impacts’ or ‘due to impacts’?
Line 88. Change ‘particles both’ to ‘particles are’
Lines 92-94. Rewrite this unclear sentence.
Line 95. Add ‘a’ after ‘plays’
Line 194. ‘evaporate’ or ‘sublimate’?
Lines 195-203. This presentation of reactions seems unusual, particularly the Net HCl+NO2+2O3 reaction. Once ClO is formed in k3, by far the most likely fate is to self-react and form ClOOCl. ClO can also react with BrO. But as shown, k4 appears to be the only fate for ClO. An alternate approach to the current presentation, which I believe is far more common would be to change the presentation order to first list the reactions k1, k5, k6 as k1, k2, k3. After these het reactions are listed, rename k2 and k3 to be k4 and k5 to show the fate of the het reactions is to generate Cl atoms and cause O3 loss. The k4 reaction can become k6, and then delete the Net reaction.
Line 219. Define NRL.
Line 271. Fig 2d,e should be Fig 2c,e
Line 271. 25.55%: 4 significant figures are not warranted. Round to 26% here and other places this number is shown.
Section 4.2. Figures 3a-d are never called from the text.
Line 289. Delete ‘is’ before ‘promoting’
Line 297. Delete ‘occurs’
Figure 4. Remove the delta on the y-axis label for panels e-h
Line 333. Figs S5 and S6 are called here, but Figs S1, S2, S3, and S4 are never called from the main text.
Line 354. Add ‘as the core’ to the end of the sentence
Figure 6. If the MLS comparison figures for the chlorine species are going to be in the supplemental rather than the main paper, they need to be called from the main text. And the poor model agreement for ClO needs to be discussed.
Figure 7 caption. Change ‘millions’ to ‘million’ in the first line. Change ‘a area’ to ‘an area’ in line 4. Change ‘Panels (b)-(e)’ to ‘Panels (c)-(f)’
Line 411. It’s very hard to believe that 0.002 ppm is significant within uncertainty.
Figure 8. There are too many lines on panel a, such that it’s hard to distinguish them.
Lines 542-547. Be clear here that these are model results, not measurements. Although, some summary comparison with measurements in the Conclusions would be useful.
Conclusions. A number of previous related studies are mentioned on lines 31-38. I suggest adding some summary text in the Conclusions highlighting the core takeaways that are unique to the present study.
Citation: https://doi.org/10.5194/egusphere-2026-3619-RC1 -
RC2: 'Comment on egusphere-2026-3619', Anonymous Referee #2, 17 Sep 2026
Overall comments
The paper uses chemical transport modelling to investigate differences in the regions around the stratospheric ozone layer in the ozone hole season following the Hunga eruption in 2022. The focus is on the first Antarctic spring, where the Hunga water vapour was present within the stratospheric polar vortex and to analyse the different chemical processes in the core and edge regions of the polar vortex and their influence on ozone loss during the spring. Comparison to MLS observations shows good agreement of the model to observations. The paper reads well, however, not all the data presented in the figures is discussed. Care needs to be taken to make sure only the relevant data is shown and/or that everything presented in the paper is discussed and referenced in the text. There are some parts of the analysis, where I don’t agree with the numbers taken from figures, attention to detail needs to be used, when looking at the data again and fixing the discrepancies between the figures and the text. I recommend publication after fixing the issues and inconsistencies as described below as general comments and line-by-line comments. Comments on the figures are collected at the end.
The use of the word “experiment” in a model study should be avoided, as it is not actually an experiment. A different choice of words should be employed to replace this. Suggestions for more appropriate words: scenario, case, perturbation, please use a different way of defining what is essentially an anomaly or difference calculation between two model simulations.
In the discussion, please make sure the numbers in the text match the figures. I have highlighted below a few places where either the numbers or timings do not match the figures as I read them. Either the visuals are off or you need to check the numbers taken from the figures, please.
Please check very carefully the need of all the individual panels and/or whole figures in the main text and SI, currently, I only see the discussion/reference to two of your six SI figures, suggesting that you only need the two. If you wish to include all SI figures, you need to edit, expand or reference the SI figures (as well as panels in main figures that are not discussed in the text currently).
Line-by-line comments
Line 26: The sentence that starts “Both observations and modelling show…”. Conceptually, only the observations show something that has happened; however, the model agrees/confirms this finding. “Show” in the latter meaning should be separated from observations. I think this should be rephrased. The simplest option is to start with the observed “thing”, i.e., from your sentence: “The H2O did not reach the Antarctic until…” and then end with something to say “modelling efforts/studies are in agreement with observations.”
Line 54: You define Stratospheric sulfate aerosol as SSA, this abbreviation is very commonly used for sea spray aerosol, so maybe re-think this. Also, you don’t use the abbreviation consistently in the paper, I suggest removing this and spelling out the three words as I think an abbreviation is unnecessary.
Line 84: first mention of NAT without spelling out the abbreviation. You do need to define NAT as this is used heavily in the paper and it should be here in the first mention of it. See line 86, where you do spell it out, move that here. Also include the chemical formula here at the first mention, see line 88, where you include it.
Line 86: Definition of NAT, move to line 84.
Line 88: Chemical formula for NAT, move to line 84
Line 125/126: First text mention of the solid and dashed lines in figure 1. They are not solid/dashed in the figures (both number one and the following figures). See overall comment.
Line 145: When I look at figure 1b, it looks like NAT PSC threshold is met in late June, not July, as you write. Please correct this.
Line 147: Please add that this sentence (end of ice and NAT PSC occurrences) refers to the edge minimum panel 1d, it is not clear as it currently is.
Line 179: using k1-k6 as reaction labels, I would expect them to be listed as numbers for the reactions on the left or right of the reactions, not to look like the rate coefficients. It is a little unusual to label reactions this way, please use more conventional labelling. As you don’t discuss rate coefficients there’s no need to present the reaction labels as such.
Line 185: HOCl is mentioned here as produced in reaction k5 and removed by photolysis. You should add a sentence on reaction k6, which also removes HOC l heterogeneously. Currently reaction k6 is not discussed in the text, if listed as an important reaction, you need to discuss it. Alternatively, you should remove the k6 reaction. In my opinion, adding a sentence on HOCl+HCl is the best option.
Line 219: Please spell out NRL, only mentioned here this once, and it should be “the NRL … model”
Line 220 & 221: Two comments on the model input: “until December 2024”, “from January 2017”. What is the start date of these datasets, before the changes you highlight. That is relevant information to include here.
Line 232 % 233: “starts in 1979”, “throughout the Hunga period”. What is the Hunga period? Here is this first mention of your simulations, and this needs to include the end time of the simulations. It is mentioned somewhere further along in the paper, but the current section is the method section, where one would expect and need this information to be located. Please add it here, preferably to quantify “the Hunga period”
Line 239: by your own definition, “experiments” here should be “simulations”
Line 240: Here you mix together your definitions again, like above. “ΔWater_vapour simulations, Control_G and Hunga_H2O”. Please be clearer in the definitions and either use “we focus on the ΔWater_vapour experiment = Hunga_H2O - Control_G” or “we focus on the simulations: Hunga_H2O and Control_G”. I prefer the first option, as this is how you use the experiment definition throughout the rest of the paper. See overall comment regarding the use of “experiment” for model simulations
Line 256 or 258: please add a reference to the MLS v5 level 2 data, i.e., Livesey et al., including the specific link to the MLS data:
Livesey, N. J., Read, G., Wagner, P. A., Froidevaux, L., Santee, M. L., Schwartz, M. J., et al. (2022). EOS MLS version 5.0x level 2 and 3 data quality and description document [Dataset]. Technical report JPL‐D105336 Rev B. Retrieved from https://mls.jpl.nasa.gov/data/v5‐0_data_qua lity_document.pdf. Data retrieved from https://search.earthdata.nasa.gov/search?fi=MLS
Line 266: Your abbreviation is not spelled out properly, “volume” is missing in “H2O mixing ratio (vmr)”, please add this.
Line 271: the yellow line is in Fig 2c,e – you have it as panels d,e. Please correct this. And: the combination of “~” and four significant numbers in the “~25.55%” is not appropriate, I don’t think you know this at that levelk of accuracy. I would choose to write “~26%” and use this throughout as this is a percentage you repeat in many places later on.
Line 287: As written how is the earlier appearance of the PSC seen at the end of the season? Please rephrase to avoid this misunderstanding. I assume you are trying to say the magnitude of the anomaly is especially important at the beginning and end of the season? If so, I don’t agree: The difference in all panels (e-h) is highest in the beginning of the season, and then gradually reduces (with panel also having negative differences at lower levels), I wouldn’t say that this follows your overall statement, I see the beginning of the season as standing out in magnitude of the difference, but not the end. Please comment and rephrase this.
Line 307-308: As written, this seems misplaced in the dehydration section. I suggest you rephrase the sentence to focus on the water loss from the denitrification. I.e., “… by NAT PSCs will contribute to removal of H2O along with the removal of HNO3.”
Line 319: I see the return to near zero from beginning of June, not July as you have written. And even then there’s still a negative anomaly at high levels ~550-650 K. Please correct the month.
Line 323: Reference to “Fig. 5”. I think your point in the sentence is clearer in figure 4c,d, please correct this.
Line: 327: “denitrification bottoms out”, please rephrase “bottoms out”, use terms more towards “chemical saturation” instead.
Line 333a: Reference to figure S5 and S6 is the only reference to any SI figures. If you leave the text as it is, then these two figures should be: 1) re-labelled to be S1 and S2 as they are the first mentioned from the SI in the main text and/or 2) these two figures are the only figures in the SI. Figures/information in the SI need to be referenced in the main text to warrant their inclusion. The discussion further down needs to be edited to include the remaining SI figures, if you want to keep them in the SI of the paper.
Line 333b: The sentence starting with “From experiment ΔWater_Vapour…” needs to have a reference to which figure you are discussing, please add this after HNO3, before the colon.
Line 334: If you refer to figure 5 (see comment above) then I see a change of ~-2 ppb, not 5 as you have written.
Line 336: I read the figure as “480 K and 450K of ~1 pbb.”, please check and correct numbers.
Line 338: highest values “in the middle”, I don’t understand what you mean here. In the middle of what? Vertically? Middle of the core? Middle of the anomaly? Please clarify.
Line 342: Add the panel after “second stage”, i.e., “5e”, so the reader knows where to look
Line 345: “has vertically narrowed” – I disagree with this. In most of the figure the positive anomaly has the same width, however it has shifted down vertically. Even if you wanted to say it has narrowed in the southernmost part, the figure cuts off lower pressure levels, so we don’t have the data present to show that in the current figure. Please clarify. Also, add the panel label in the figure reference, should be “5c”
Line 344: “become confined” – I disagree: Please add a qualifier “become mostly confined”
Line 352: another occurrence of “bottoms out”, please rephrase, see comment above.
Line 356: add “chlorine” in “active chlorine species”
Line 357: Please edit the sentence to “…rapidly until July, and …”, leaving out June
Line 360: Please add the figure reference, I think figure 6c
Line 364: after “from mid-August” add a reference to the figure, i.e., “(Fig. 6a)”. It is not very clear which panel the reader should focus on otherwise.
Line 367: Add “(Fig. 6a) after “mid-September”.
Line 368: “before the gradient was reduced” reads as not needed or confusing. If you want to comment on the changing gradient of the reductions, please elaborate on this point. One way could be to delete the highlighted text and replace it with the month this occurs. After this adding a sentence on the changing gradient of the HCl decrease could be added if you want to.
Line 370: add references to figure 6e,f and the end of the sentence, please.
Line 373: “However, unlike the core” – I disagree, they edge and core are not that significantly different on this point. Please rephrase.
Line 376: “much less distinct reduction” – 1) there are too many qualifiers on this term, making it difficult to follow your point, 2) I disagree, comparing 6a with 6b, 6b shows no reduction at all, however, 6h shows larger magnitudes of increases and decreases than 6h. please rephrase accordingly.
Line 376: “reduction is initially small…increasing after…up to a maximum of…” It is confusing to have a reduction that increases up to a maximum. A reduction can become more negative and reach a minimum, i.e., “become larger in magnitude” or “decline to a minimum” or similar. Please rephrase this to clarify.
Line 383: please add “~450K (Fig. 6c)” after “end of the season” to point us toward the core region panel.
Line 385: The figure reference should be to panel 6d, please correct this.
Line 388: Add OClO to the definition of ClOx – I assume you do include it in the calculation?
Line 389: “… as the season progresses, the difference becomes less …” This sentence doesn’t make sense You need to split the two points covered in the sentence: 1) ClOx increasing dramatically in the beginning of the season to a slower increase until ~mid-August, where a slow decrease starts, ended with a drastic decrease at the end of the season for one level in fig 6a and 2) the difference between the Hunga_H2O and control_G simulations is reducing in magnitude from the beginning of the season until the end. Finally, a separate point is if the difference between the Hunga_H2O and control_G simulations which shows a positive anomaly in the beginning of the season, reduced to nothing and followed by a small decrease at the end of the season in fig 6c for ClO can be representative for ClOx? Looking at 520 K in 6a (ClO vs ClOx) this is not the case. Please rephrase/rethink the analysis accordingly.
Line 390: “…initial increase that is maintained throughout the season…” – I disagree, in comparison to the core region, you show the edge region as increasing at a slower rate to the core, peaking mid-July and then slowly decreasing until the end of September, finishing the season with a sharper decrease towards zero at the end of October in fig. 6b. Please rephrase to reflect the data shown in the figure.
Line 400: “… very low levels…” what do you mean here? Concentration levels? Pressure levels? Please clarify in the text – I assume you mean concentrations, but please add which concentrations and if you mean to compare fig 6a,b. Later in the sentence “…maintains a reduction in reservoir species…” compared to the core that reaches zero. This doesn’t make sense the way it is phrased, it reads as though you mean to say that the maintained reduction in the edge region is more reduced than the core region but then follow that by saying the core reaches zero. Please rephrase this whole sentence – I think you want to say that the changes in the core region are more drastic than the edge region and both reservoir species almost reach zero in the core, whereas the HCl is not reduced as much in the edge and ClONO2 is unchanged or increasing rather than decreasing in the edge across the vortex season.
Line 404: “… PSCs are not as effective.” – effective at what? Please add this information to the sentence.
Line 408: “…small amount of ozone loss of up to -0.05 ppm” – there’s also a small increase in ozone before the season at ~575-750 K in Apr-May, please include this information.
Line 410: Surely, the number in brackets should be positive? “+0.03 ppm”, you say it is a small increase, please correct this.
Line 419: Please add reference to the figure, i.e., “…ClO increase (Figure 6d), alongside…”
Line 420: Please extend the period to match the figure better: “late September through October as the ozone…” and please add references to the figure panels in the text: “…additional HCl increase (Fig. 6e)…” and “with a ClO decrease (Fig 6c)…”
Line 421: As above, please add reference to the figure: “…regime of near zero ozone (Fig. 7c).”
Line 422: Add reference to the figure at the end of the sentence: “…period and smaller areas (Fig. 7d).”
Line 435: Fig. 8, not 7, please correct this.
Line 442: “Dumont D’Urville” – needs more information about the location and the “D” should be a small letter, so i.e., “the Dumont d’Urville station, Antarctica” is a suggestion to use instead.
Lines 448-450: Regarding the four area numbers: Do you really need this many significant numbers, when they are in millions? I suggest rounding, so you only have two significant numbers in all four numbers mentioned in these lines, i.e., 24, 26, 1.7, and 7,2.
Line 453: typo “…the the PSC…”
Line 454: Another rounding off: please round off the percentage to 25%.
Line 470: “…continue to remain…”, please simplify/correct the language here: “continue to be” or “ remain”
Line 476: “larger than 2023… and towards the end in mid-December” – I disagree, looking at Figure 8b, the purple and dark pink lines are indistinguishable from the end of September until mid-December, where the purple line is lower for a while. 2024 is not larger than 2023 as it is written in the text. Please correct this, i.e., simply delete the text: “and towards the end in mid-December”.
Line 480: Please add more text here to be more precise: “…example after the eruptions of El Chichón, 1982 (e.g., … and Mount Pinatubo, 1991 (Hofmann….”
Line 482: First mention of figure 9. Somewhere here it should be mentioned that Fig 9a,b are identical to fig. 7a,b.
Line 487: Please add two commas in this sentence – it changes the meaning of the sentence to what I assume you want to say: “descends, with positive values above, and gradually diminishes…”
Line 489: Please add “losses of” in “ with losses of 0.08 ppm in the core…”
Line 506: This sentence should be clarified, particularly: “…the additional ozone (positive) relative to the…was 40% less for both regions…” How can this be both positive and 40% less than what you compare it to? Please elaborate and clarify what you are trying to say here.
Line 508: Delete “Therefore,” rephrase and start with “Overall the chemical impact on…”
Line 520: “… the higher solubility of HCl in (liquid) PSCs than organics…” – I would like to see a reference for this added to this sentence.
Line 540: Again, please round off to “25%”
Lines 544-545: “…that are not maintained…” and “…only 0.12 ppm in September 2023.”
Line:555: Rounding to “1.7 million km2”
Line 556: “a control simulation” – Please specify which one, you have used one with 2022 aerosols and one that was “clean” with 2017 SAD.
Lines 565-567: merge this text with the paragraph that ends on line 559, as these lines repeat some of the information in lines 557-559. I suggest that you keep the reference to ERA5 and the last sentence in lines 566-567 and merge the rest into the paragraph above.
Line 569: MLS url: please be more specific and add the MLS direct link:
https://search.earthdata.nasa.gov/search?fi=MLS
Lines 596-602: both Bednarz et al papers and the Brühl et al. paper have been published now
Lines 790-791: Wargan et al has been published.
Comments on figures
General comments on figures
I like that you have four distinct lines showing the PSC thresholds and the +2K of the thresholds, however, in all the text you refer to these as two solids lines and two dashed lines (and in one case in colour), which they are not. Please correct this throughout the paper.
Some figures have boxes around the legend for the threshold/temperature lines, some don’t, please be consistent and remove the boxes.
Header for rows of panels are not consistent between the different figures. Sometimes you have the model name, sometimes not, other times you use the simulation names, i.e., “(Hunga – control)”, whereas you mostly refer to this as Hunga_H2O – control_G or ΔWater_vapour, or you write out the word “Delta”. Please be more consistent with this. I suggest using the “ΔWater_vapour”-style and include thes row headers for all figures
Use the delta symbol in the first part of the headers, i.e., for the PSC area (figure 3) as “ΔIce PSC area” or simply remove the word “Delta” as the colourbar is labelled “ΔPSC area”.
Finally, some of the colour choices are difficult to tell apart, particularly the yellow lines in figures S5 and S6, please think about other options to make all data more visible in all figures.
Specific comments on figures and captions
Figure 1: The threshold lines are not shown as described in text or caption. Panels b and d are particularly difficult to read, panel b because there are additional lines that shows something else than the thresholds (I think a repeat of all four lines from panel c?) and panel d, because the lines are very close together. In the text and captions the threshold lines are described as red and black solid and dashed lines; however, this is not the case. The use of different types of dashes work just as well as using two colours, but as it is, only the legend has the correct labelling I assume. Please check and correct this figure and associated text. Readability in panel d could maybe be achieved by re-scaling the figure, a suggestion, but please improve readability in some way.
Figure 2 caption: misplaced delta symbol, please delete this or rephrase to use the “ΔWater_vapour” terminology instead. The latter would be cleaner and yields an additional purpose to defining your delta-model runs. Please add the point that the threshold contours are the minimum ones from fig 1 to clarify.
Figure 4: panels e-h have a colourbar labelled with delta HNO3, please remove the delta-symbol, which is misplaced and write “HNO3 vmr” instead. The bottom colourbar has two flat ends, should be an arrow for the top one labelled 15 to be consistent with the other figures.
Figure 5: many of the panels are not discussed in the text, mostly the three panels regarding HNO3, which could suggest that either the figure is reduced in number of panels, moved to SI or more analysis of the data is added to the text.
Figure 5 caption: there are no purple or grey lines and the yellow lines are difficult to read, maybe use purple here? Or a different colour. It’s fine that the threshold/temperature lines are black keeping consistency with the other figures in the paper.
Figure 6: All anomaly panels 6e-h have the colours reversed compared to the rest of the figures in the paper, please switch these back to red = positive and blue = negative to match all the other figures. Only six species are visible in panels a,b – for clarity please remove the four redundant species from the figures (Cl, Cl2, OClO, BrCl) and change the colours somewhat to make it easier to distinguish between the different species, as it is now Cl2/ClO and Cl/Cly could be seen as the same colour, respectively.
Figure 8: legend is in a jumbled-up order in my opinion. The lines and colour should be grouped together and/or the header to say “pre-Hunga years” need to be above 2015, Calbuco. The two black years for 2020-2021 are indistinguishable, maybe this is what you want(?), and why are these two lines thinner than all other coloured lines? I assume that the years before 2022 are all from the long background run, also including 2015, which is the same thickness as the Hunga years 2022-2024. Please fix these inconsistencies.
Figure 8 caption: “The ozone hole is calculated using the 220 DU threshold.” This sentence requires more explanation in the main text, please add this. It is not enough to have this information in the caption. The text here in the caption is enough for a caption, but you need to explain why this threshold is used here in relation to past work/observations.
Figure 9: only figure to have “Jan” written at the end of the x-axes, please remove these for consistency. Also replace the x-axis label with “ΔO3 (ppm)”. This figure doesn’t have the row titles, I think that is a mistake, this one in particular would benefit from them. I suggest adding the label for your experiments as the headers, i.e., “ΔWater_Vapour”. Finally, the title should include “ΔO3” instead of “O3 absolute Δ”, in better agreement with the style of all other figures.
Figures S1 and S2: the “L” in the labels on the colourbars are capital, these should be small: “HCl” and “ClO”. In these two figures panels a and b are shown in the main text as figure 6 panels c-f, this should be mentioned. Also here the S1a,b and S1a,b have the red-blue colours in the “correct” way, meaning blue is negative and red is positive in alignment with all other figures you show.
Figures S3 and S4: the style of these figures are very different to the rest of the figures in the paper, it would be nice if they were more coherent, please update these (if you choose to keep them, see general comments).
Figures S5 and S6: the yellow lines are almost impossible to see, please pick a different colour that will still show on top of the colour gradients.
Figure S5and S6 captions: Please add “changes” or “differences” in the first line of the caption: “…modelled differences in H2O, …”. Add mention of which set of simulation are used here, i.e., in the form “ΔWater_Vapour”
Citation: https://doi.org/10.5194/egusphere-2026-3619-RC2
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I have read your study with great interest and for me it was a very interesting and well done study of the impacts of the Hunga Tonga eruption on the Antarctic polar vortex in 2023. However, the manuscript in its current form is quite lengthy and would benefit from some shortening. Further, there are also a lot of small typos, especially obsolete spaces before commas and full stops, that should be removed before publication. There are also some other issues that could be improved to make the text and results presented more concise.
I will list in the following my comments and technical corrections:
General comments:
The figure main titles are rather obsolete since all information needed is provided in the caption and the text. The only titles that should be kept are core/edge and dates.
Using subsections for the introduction is rather unusual and I would suggest omitting these and trying to adjust the text flow that it will be one continuous text.
I would suggest to swap section 2 and 3, thus starting with the model and measurement data description and then describe the metrics. I also think it would be better to have both data and metrics in one “Method” section.
As mentioned above, the manuscript is quite lengthy and some shortening would make it much more concise.
The lines in the figures should be improved for better visibility, especially the PSC temperature threshold lines. I would suggest to use additional different colours or line thickness.
Figure 2, 4 and 7: The comparisons to MLS are quite nice and show the good agreement of the model simulation with the measurements. However, since this comparison is not the major focus of the study you may consider to move these figures to the supplement.
The summary and conclusions should be improved to be more concise and to provide a better statement on the implications of your results.
Specific comments:
P3, L89: In the classical classification using type Ia, Ib and II it was always assumed that type II forms homogeneously and consists of pure ice. Later it was found that ice can also form heterogeneously on NAT or on other small particles as e.g. meteoric dust. However, to be consistent at this place in the text with the classical PSC types I would suggest to write that ice is composed of H2O and NAT of HNO3 and H2O.
P4, L93: Lidar measurements and model simulations show that STS forms already when temperatures drop below 195 K. Note, the 195 K threshold is the NAT existence temperature, not the formation temperature. NAT forms usually at temperatures around 190 K (dependent on the formation process), but can exist up to 195 K.
P5, Fig. 1 caption: There is no red line. Please check the caption text and correct.
P6, L161: Here you could cite also other studies discussing the occurrence of ozone mini holes in the Arctic as e.g. the study by Hommel et al., ACP, https://doi.org/10.5194/acp-14-3247-2014 for the 2010/2011 winter.
P7, L179: I guess k1 to k6 refer to the reactions given below. However, at that place in the text this is not clear. A reference to the reactions given below is missing.
P7, L186: Not clear. Isn’t that a contradiction? Why can the HNO3 production contribute to denitrification?
P7, L194: Supported is not the correct wording here. Simply temperatures are too warm for the PSC particles so that these evaporate.
P7, 195ff: Add numbers for the reactions.
P8, L210: What exactly is meant with saturation threshold? You mean the saturation pressure? More explanations should be provided here to be more clear.
P8, L219: What is NRL? The abbreviation has not been introduced.
P8; L227: How has this given value for the fall velocity been derived? Has this been calculated or derived from a parameterisation?
P9, L240: delta_Water_Vapour denoted here as “simulations”, but not listed in Table 1. I guess you mean experiment instead of simulation.
P10, L273: Which band? Do you mean edge?
P13, L290: Not clear what you mean with slightly higher temperature thresholds.
P13, L308: In the Antarctic ice PSCs will rather consist of pure ice due to the very low temperatures and thus contribute mainly to dehydration. Even if they contain NAT, I am not sure if this will have a huge effect on denitrification. If there are studies showing that also ice PSCs containing NAT contribute to denitrification you should mention these here. Generally, I would suggest to phrase the sentences more carefully to be more precise and avoid misunderstandings.
Figure 5: Denitrfication/re-nitrification rather difficult to see. I would suggest to consider changing/adjusting the colour scale or adding boxes/circles to mark the respective areas.
P18, L383: Around which temperature fluctuations? You are not showing any temperatures.
P20, L440: Hunga report? I guess you mean here the APARC report on the Hunga Tonga eruption. You should be more precise here with the reference.
P25, L530: Sentence “For this purpose, the model predicted chemical impacts from the
Hunga H2O were analysed using an equivalent latitude co-ordinate system” not clear. Please rephrase.
P25, L552: Sentence “It is possible the edge could be used to assess the impact of a Hunga-like eruption in a warmer winter and is potentially transferable to the Arctic” not entirely clear and should be rephrased. Generally, I would also suggest to more clearly write here and throughout the manuscript “edge region” and “core region”, respectively, instead of just “edge” and “core”.
P29, Reference of Davies: Correct first name initials.
Technical corrections:
P4, L94: Add “a” -> Stratospheric H2O plays a key role
P7, L183: Change test to: ……sedimentation of the NAT particles and subsequent denitrification…
P8, L210: Ice -> ice
P8, L230: where model had fixed -> where the model had a fixed
P9, L240, K251: Remove space before full stop.
P9, L259: process -> processes
P10, L264: Remove space before full stop.
P12, Fig.3 caption: Remove obsolete spaces.
P12, L289: Either write “This is due to “that” the additional ……”or “This is due to the additional H2O promoting……”.
P13, L293 and 301: Replace “&” by “and”
P13, L297: Rephrase sentence, I think it rather should read “that occurs in the NAT extent”.
P14, L328: Add “the” so that it reads “Therefore, it is possible that ,,,,,,,” Sentence generally somewhat difficult to read. Consider rephrasing or splitting into two sentences.
P16, L335: Avoid separation of number and unit at the line break.
P17, Figure 6 caption: Replace “&” by “and”.
P18, L395: focussed -> focused, but I would rather suggest to replace focused by found.
P18, L396: Add “PSC” so that it reads “NAT PSC”.
P19, Figure 7 caption: Replace “&” by “and” (three occasions) and change “right is the edge” to “right is for the edge” or “right is shown the edge” .
P19, L404: Here you write zero, but in other occasions you use the number 0. The wrtting should be consistent throughout the manuscript.
P20, L425: hole -> holes
P21, L447: Remove obsolete space before comma.
P22, L449: Same here.
P22, L466: so can diagnose -> thus the model can diagnose
P22, L467: metrology -> meteorology
P22, L468: Add “simulations” so that it reads “both simulations with and without…..”.
P22, L479: has -> have
P22, L481: Add “increased” so that it reads “the increased H2O, stratospheric aerosol…….?
P23, Fig. 9 caption: Be more precise and write: The left column shows the core region and right column shows the edge region
P24, l490, 499 and 504: Remove obsolete space before comma.
P24, L498: Add space between “</>“ and “number”
P24, l500: Add “that” -> It is possible that….
P24, l502: Figure 9 -> Fig. 9
P24, L523: pyrocumubnimbus -> pyrocumulunimbus
References:
Hommel, R., Eichmann, K.-U., Aschmann, J., Bramstedt, K., Weber, M., von Savigny, C., Richter, A., Rozanov, A., Wittrock, F., Khosrawi, F., Bauer, R., and Burrows, J. P.: Chemical ozone loss and ozone mini-hole event during the Arctic winter 2010/2011 as observed by SCIAMACHY and GOME-2, Atmos. Chem. Phys., 14, 3247–3276, https://doi.org/10.5194/acp-14-3247-2014, 2014.