the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Stratospheric water vapor and ozone response to different QBO disruption events in 2016 and 2020
- 1Institute of Energy and Climate Research, Stratosphere (IEK–7), Forschungszentrum Jülich, 52 425 Jülich, Germany
- 2Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany
- 3Department of Meteorology, University of Reading, Reading, UK
- 4Laboratoire Atmosphères, Milieux, Observations Spatiales, UMR CNRS 8190, IPSL, Sorbonne Univ./UVSQ, Guyancourt, France
- 1Institute of Energy and Climate Research, Stratosphere (IEK–7), Forschungszentrum Jülich, 52 425 Jülich, Germany
- 2Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany
- 3Department of Meteorology, University of Reading, Reading, UK
- 4Laboratoire Atmosphères, Milieux, Observations Spatiales, UMR CNRS 8190, IPSL, Sorbonne Univ./UVSQ, Guyancourt, France
Abstract. The Quasi-Biennial Oscillation (QBO) is a major mode of climate variability with periodically descending westerly and easterly winds in the tropical stratosphere, modulating transport and distributions of key greenhouse gases such as water vapor and ozone. In 2016 and 2020, anomalous QBO easterlies disrupted the QBO’s 28–month period previously observed. Here, we quantify the impact of these two QBO disruption events on the Brewer–Dobson circulation, water vapour and ozone using the ERA5 reanalysis and satellite observations, respectively. Both lower stratospheric trace gases decrease globally during the 2015–2016 QBO disruption event, while they only weakly decrease during the 2019–2020 QBO disruption event. These dissimilarities in the circulation anomalous response to the QBO disruption events result from differences in the tropical upwelling caused by anomalous planetary and gravity wave forcing in the lower stratosphere near the equatorward flanks of the subtropical jet. The differences in the response of lower stratospheric water vapor to the 2015–2016 and 2019–2020 QBO disruption events are due to the cold–point temperature differences induced by the Australian wildfire, which moistened the lower stratosphere, therefore, hidding the 2019–2020 QBO disruption impact. Our results highlight the need for a better understanding of the causes of QBO disruption events, their interplay with other climate variability modes, and their impacts on water vapor and ozone in the face of a changing climate.
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Mohamadou A. Diallo et al.
Status: final response (author comments only)
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RC1: 'Comment on acp-2022-382', Anonymous Referee #1, 14 Jun 2022
Diallo et al. investigate the impact of the two QBO disruption events in 2016 and 2020 on water vapour and ozone using ERA-5 reanalyses and satellite observations from MLS. They find differences in the impact these disruption events had on atmospheric circulation and thus on the trace gas distribution of water vapour and ozone. This is a quite interesting study with interesting results. However, the writing could have been generally done a bit better and I have several suggestions for major revision before publication in ACP.
Generally, the whole study and writing is a bit too descriptive and though you state in the abstract that you “quantify” the impact it is done throughout the study in just a “qualitatively” manner. Don’t understand me wrong, I do not need for everything numbers, but if there are too many phrases using terms like “weakly”, “small”, “large” it is quite difficult to get a feeling for how strong actually the impact is. I will provide more detailed feedback on this in the specific comments.
General Comments:
- Usage of the term “2016” and “2020” and “2015-2016” and “2019-2020”. In some occasions the whole period is used and in other only the second year of the period is used. I could not really see if there is a concept when you use which term, thus I would suggest to change to one way of writing consistently throughout the manuscript or explain when you use what.
- In all figures the font size should be increased. In the supplement this should be done for Figures 1-5.
- Use the Copernicus style: Units (km, hPa,…….) are written in upright font.
- Your results are based on the measurements from one satellite, namely MLS. I remember that there are significant differences in the QBO imprint on the trace gases between different satellites. How does that affect your results? Have you done a similar analysis using another satellite instrument? What where the differences?
- Some figures of the supplement as e.g Figure S5 should be moved to the manuscript since they are discussed in detail and seem thus to be not that unimportant. There are also some other figures in the supplement that also could be moved to the manuscript.
Specific Comments:
P1, L6: “weakly decrease”. Be more precise. Decrease by what? What exactly causes the decrease? The BDC transport?
P1, L7: Here you talk about “circulation anomalies”, but before you talked about changes in the trace gas distributions (their abundance). I would prefer a clear separation in the language between dynamical processes and their consecutive imprint on the trace gas distributions.
P1, L17: Here a 1-2 sentence description what the BDC is should be added.
P2, L21: “Ozone is mainly produced in the middle stratosphere and is a good proxy for tropical upwelling”. This is generally correct, but a too simple and not correctly understandable sentence for non-experts. I would suggest to rephrase this sentence and clearly state when and where is ozone produced, how is it transported and why can it be used as proxy for transport.
P2, L27: Introduce the abbreviation “QBO” and add a sentence describing what it is. You actually do that in the next paragraph. This paragraph should be moved higher up.
P2, L29: Explain also shortly what dehydration is.
P2, L32: Shouldn’t it read “e.g. water vapour and ozone”. Doesn’t this hold also for other trace gases?
P2, L31-36: As stated in my comment on P2, L27 this entire paragraph should be incorporated in the previous paragraph.
P2, L52: ….affect the radiative forcing it the Earth’s climate system…” What does that mean? Are we (the society) affected by these disruptions? What are the changes or consequences we experience based on this disruptions? Or are these just interesting for scientists to better understand atmospheric circulation?
P3, L68-69: “….high precision and lower systematic uncertainty….” Add some numbers. How high is the precision? Lower uncertainties than what? The former MLS version?
P4, L112: Rephrase this sentence that either the references are incorporated in the text or so that these can be added in parentheses. As it is done know it is not correct
P4, L116: Differences in the disruptions. Are here references missing? Are you referring to previous studies or is this done in this study? Please clarify and revise text accordingly.
P5, Figure 1 caption: How has the onset/offset be defined? When exactly did this happen. Can you provide year/month of the respective onsets and offsets?
P6, L148: What is the “tape recorder”. A short explanation should be added.
P7, Figure 2 description: I really have trouble follow your descriptions/explanations. This is really difficult to see from the figures. Could add some guidance for the eye in the figures, like arrows or boxes or any other shape or sign that marks the respective areas?
P7, L181: I would suggest to rephrase this sentence. Dehydration refers only to H2O not to both H2O and O3. This sentence can be easily misunderstood.
P7-8: This is all bit too qualitative and difficult to see in the figures. Is there a possibility to quantify the changes?
P8, L197: How do you exactly derive the “zonal mean impact”? What has been done/considered here? The difference of the zonal means?
P8, L198: Which AOD data has been used?
P8, L198: How do you derive the impact? This becomes not clear.
P8, L216: “Also note the large variability….” Is this visible in the figures? Or do you mean these have been shown in other studies? If the latter is the case references should be added. If the former is the cause the text should be rephrased.
P9, L226: “large” should be quantified or give more information on the differences than just “large”.
P10, Figure 3 caption, 3rd line: The monthly mean mixing ratios you are referring here to; are these for the entire time period 2005-2020?
P10, Figure 3 caption: The sentence “The impact of the QBO ……….” should be incorporated into the main text rather than in the figure caption.
P10, Figure 10: The wind lines are difficult to see in detail. Thus, I would suggest to add a figure panel showing only the wind.
P11, L231ff: Can you quantify these differences?
P11, L254: about 10% weaker? How do you derive this number?
P11, L259: Fig S4 and maybe some other figures should be rather moved to the main text. It is quite inconvenient to swap back and forth between the manuscript and the supplement.
P13, L280: Add a marker/box in the figure to better visualize this?
P16, L348: “large” and “small”. Please quantify this.
P17, L354: “smaller” and “shallower”. Same here as for P16, L348.
P17, L358 and L360: This is really hard to see from the figures shown.
Supplement, Figure 3: Although you can only show here a specific altitude range, these figures is much more helpful to see the difference. I would suggest to put this figure into the manuscript rather than in the supplement.
Supplement, Figure 5: Since this figure is discussed in detail in the manuscript it also should rather appear there than in the supplement.
Technical Comments and Corrections:
P1, L1-2: I would suggest to move “in the tropical stratosphere” to the first part of the sentence so that it reads: “The Quasi-biennial Oscillation (QBO) is a major mode of climate variability in the tropical stratosphere, with ……………”.
P1, L4: Writing it like this is rather misleading. I would suggest to rewrite the sentence as follows:…..on the Brewer-Dobson circulation and respective distributions of water vapour and ozone, using…...”.
P1, L14: The line “Copyright statement: TEXT” is obsolete and can be deleted.
P1, L29: in the air parcels → of the air parcels
P3, L70: Add “e.g”. There are also other studies that document the quality of the MLS H2O data than the ones by Hegglin et al.
P3, L71: Here a capital “U” is used. Later to the wind with a small ”u” is referred. This should be done consequently throughout the manuscript in one or the other way.
P3, L81: Rephrase sentence as follows: “In the figures only the 2013-2020 period is shown to highlight the two QBO disruptions.
P4, L92: Introduce abbreviation “ENSO”.
P4, L95: Introduce abbreviation “AOD”
P4, L99: In In → In
P4, L105: are → were
P5, Figure 1 caption: “U” or “u”?
P7, L158: 3_3 → O_3
P7, L159: I am not entirely sure, but I would add “a”, so that it reads “we performed a regression analyses”
P7, L163: \citet instead of \citep
P8, L186: disrution → disruption
P9, L221 and L225: JAS → July-August-September (or July-to-September)
P11, L227: add “phase” or “winds” after “easterly”
P11, L229: JAS → July-August-September (or July-to-September)
P12, Figure 4 caption: “Tropical averaged of the deseasonalized mean” should be either changed to “Tropical averaged deseasonalized mean residual velocity” or to “Tropical averages of the deseasonalized mean residual velocity”.
P13, L284: move “in the following” before “we finally” so that it reads “in the following we finally investigate…….”
P14, Figure 5 caption: space between “(NetF)” and “(a,b)” and between “(contours)” and “easterly” missing.
Supplement: Check the figure captions. The units should be in upright font (same holds for the manuscript) and in several occasions the O in H2O is in italic instead of an upright font.
Supplement, Figure 3 caption: Add which line is the blue one and which is the red one.
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RC2: 'Comment on acp-2022-382', Anonymous Referee #2, 30 Jun 2022
Diallo et. al use ERA5 data and Aura Microwave Limb Sounder (MLS) satellite observations to quantify the impact of anomalous QBO events that occured in 2016/2017 and 2019/2020 on the Brewer-Dobson circulation, water vapour and ozone. They highlight the importance of understanding the reasons for disruptions in the QBO because of its impact on climate research within a changing climate by making use of multiple regression analyses to separate the impact of the QBO on the circulation, ozone and water vapour.
General comment:
The paper is well written and well structured, but needs some more precision in some points to make concepts clearer (indicated below). The text is often very descriptive and it easily becomes tedious to read, but this is necessary in order to build the storyline and possible omissions have been applied where concepts for the first QBO disruption are similar to the second. The supplement only contains figures which are used extensively in the text. An effort should be made to include the really necessary images in the text and only put figures and add explanatory text in the supplement that is not necessary to understand the idea behind the paper. It does not help the reader to have to refer to the supplement to understand the main text.
Specific and technical comments:
Most comments I have are questions about understanding and precision.
I noticed that you mix American (A) and British (B) spelling (center (A) vs centre (B), vapour (B) vs vapor (A)). Could you check for consistency?
Line 1: What do you mean with “major mode of climate variability”? Do you want to speak about the disruption as a change to the QBO as a mode of climate variability? Climate change impacting this mode?
Line 3: It sounds as if there was a fixed 28–month period for previous QBO periods when in fact it varied before. Maybe giving a range indicating in what the disruption consisted is better here.
Line 5: Better write “Both, water vapour and ozone in the lower stratosphere” instead of “Both lower stratospheric trace gases”
Line 7: Do you mean “anomalous circulation response“ instead of “circulation anomalous response”?
Line 11: Do you mean “hiding/obscuring/concealing” instead of “hidding”?
Lines 21/22: The two following sentences essentially say the same thing: “Ozone is mainly produced in the middle stratosphere and is a good proxy of the tropical upwelling. In addition, ozone variability in the tropical lower stratosphere is affected by variability in tropical upwelling of the BDC.” Please revise.
Lines 24/27: Do you mean “natural climate variability, including the QBO” or “modes of climate variability, such as the QBO”? The term “natural mode of climate variability” is confusing.
Lines 33/37: “oscillation between tropical westerly and easterly zonal wind shears” Do you mean “oscillation of the zonal wind”? The easterly and westerly shear zones descend differently.
Line 34: “QBO phases” You have not defined what you mean with phase, here. Looking at a vertical profile the QBO has easterly and westerly phases at different altitudes, so for the Brewer-Dobson circulation one might argue that there is on average no influence.
Line 38: It was not the “anomalous QBO westerlies” but the “QBO westerlies” that got disrupted (by an anomaly).
Line 44: I would write “climate change“ instead of “climate changes”
Line 46: Osprey et al 2016 do not mention CMIP6?!
Lines 54/55: This sentence appears not to be grammatically correct because verb and substantive have similar forms. It is better to reformulate the sentence, e.g: “Here we use satellite observations to quantify the similarities and differences in the strength and depth of perturbed/disrupted QBO effects in 2015-2016 and 2019-2020 on water vapor and ozone in the lower stratosphere. “
Lines 60 to 63: Please reform the sentence to make your statement more lucid. The same issue of verb and substantive confusion might occur especially for the non English native reader. You probably mean something like: “Finally, we discuss the main reasons for the anomalous differences in BDC and UTLS composition between the 2015-2016 and 2019-2020 perturbed QBO effects associated with planetary and gravity wave dissipation, which are likely caused by the anomalous surface conditions associated with the strong El Niño Southern Oscillation (ENSO) in 2015-2016 and the strong Indian Ocean Dipole (IOD) in 2019-2020. “
Lines 63/64: Maybe better: “We also discuss the differences between 2016 and 2020 in terms of the particularly warm stratosphere in the context of Australian wildfire smoke in 2020.”
Line 69: “lower systematic uncertainty” lower with respect to what?
Line 70: It is better to explain “multi-instrument mean”? From the text it is not obviously clear what you mean without reading Hegglin et al., 2013, 2021
Line 71: I presume that the ERA5 data used is also 2005-2020?
Line 79: “…impact on these monthly…” should be “…impact on the monthly…” or “…impact on the MLS monthly…”
Line 81: “To highlight the two QBO disruptions, figures only show the 2013–2020 period.” Do you mean “To highlight the impact of the two QBO disruptions, figures only show the shorter 2013–2020 period.”?
Is the water vapour and the ozone from ERA5 much different from the MLS data? Because it would actually be really good to see the impact of the QBO on water vapour and ozone from 2005 to 2013 to visually see what “normally” happens, maybe as supplement.
Line 89: In this context (mathematical, technical) I prefer “indices” over “indexes”. See for example https://books.google.com/ngrams/graph?content=climate+indexes%2C+climate+indices&year_start=1950&year_end=2019&corpus=26&smoothing=3&case_insensitive=true#
Line 90: Please define “tropical” here. (for example averages over 5°S to 5°N)
Line 93: Please define “AOD”
Line 95: “The solar forcing is neglected because our data set is relatively short.” You have a data set comprising 16 years. That means that you have more than one solar cycle. I don’t think that this is short, especially not because a linear trend does not take into account the end of solar cycle 23 and solar cycle 24. Have you checked whether it matters? Is it too much work to include the solar forcing?
Line 99: There is an “In” too many at the beginning of the sentence.
Line 99: “unexpected tropical QBO easterlies (negative QBOi) developed in the center” Here “in the center” is not clear, what is the center of the QBO? Is there a center? Over which altitude does the QBO exist? There are many questions that you raise by using “center” here. Maybe it is better to say at 22 km). Furthermore, it seems that the disruption already starts earlier that where you indicate at an altitude of 32 km. As the wind shear seems to shift downwards the disruption of the QBO may have been started earlier. By emphasizing your study on the disruption in the altitude range 15 to 24 km you might oversee something? Or are there two independent disruptions, one aloft and one starting at 22 km? The interesting thing is why at 26 km the westerlies persist.
Line 112: The references should not be in brackets.
Line 114: Here you use “center” again. Better indicate the altitude range or ‘center of the image’.
Line 119: You say that the disruption is visible in the water vapour ozone plots. This is difficult to judge if you only show 2013 to 2021. In the water vapour plot it even looks as if water vapour shows a strange behaviour before the onset of the disruption in 2016 that you indicate. Which would point towards a previous event maybe the onset of easterlies at 32 km at the beginning of the year. Tropical ozone anomalies are closely related to temperature anomalies show the QBO disruption, as you say, and are therefore to be expected.
Line 125: “is the most effective” should be “is most effective“
This sentence is not clear. Do you mean that the disruption impacts tropical upwelling via its impact on tropical upwelling? Do you mean the water vapour anomaly minimum at 17 km and the ozone anomaly minimum at 16 km the end of the disruption that you indicated? What do you mean by “when the signal reaches”? Why do you think that this is due to the disruption impact on tropical upwelling (if this is what you meant to say)?
Line 127: You refer to the wind at 30 hPa but this is not shown in the figure. Please add the pressure altitudes to the figure or indicate altitudes in km (with pressure in brackets) whenever you mention pressure altitude in the text. Also indicate where this event happens. Do you mean at 26 km between the two vertical lines indicated, i.e. the uninterrupted westerlies during the disruption?
Line 129: I would not speak about an upward shift of the westerlies. Westerlies are rather maintained longer and reestablish at the top moving downwards.
Line 133: “substantially increased H2O mixing ratios and decreased O3 mixing ratios” do you mean “coincided with an increase of H2O mixing ratio anomalies and a decrease of O3 mixing ratios anomalies”?
This is true for water vapour anomalies but for the ozone anomalies there is an earlier onset with a slight increase and it does not reach as high up as the water vapour (25 km).
Line 134/135: “sudden occurrence of the QBO 135 disruption”. An interesting question here is if the disruption was not caused by this, and the ozone and water vapour response is just due to the thermodynamic balance.
Line 138: the spelling of structural is wrong here (strutural).
Line 145: “compare” should be “compared” (or compares but then there should be an “and” before “suggests”.
Line 147: Figure S3 is mentioned before S2 please switch the order of the figures.
Line 158: Spelling: “33 anomalies” should be “O3 anomalies”
Line 160: “The difference… gives the QBO-induced impact.” Is it not only “the linear part of the QBO-induced impact”?
Line. 170: I don’t really see this. I presume that you refer to the region between the two vertical lines. There ist seems the other way round? Or for water vapour it is negative when the QBOi increases (from negative to positive).
Line 171: Here I would only mention that the ozone anomaly changes follow closely the disruption in the zonal wind. I would not speak about suddenness.
Line 173: Here it would help to have the months as minor tick marks. I can see the alignment with ozone but for water vapour this is only speculation and is not true further up, i.e it might only be true for one altitude level.
Line 179: 40 hPa please also give the altitude.
Line 179/180: The response is different for the ozone and water vapour anomalies. For ozone the altitude range and the temporal extend true but for water vapour it is rather from mid 2016.
Line 182: “anomalously cold point temperatures” should be “anomalously low cold point temperatures”
Line 183: Why is there enhanced tropical upwelling?
Line 184: “indueced” should be “induced”
Line 186/187: I don’t understand:
1st statement: disruption induced O3 anomalies are small between 2016 and 2020
2nd statement: disruption induced O3 differences are large between 2016 and 2020
I am not sure what you want to say here. Could you reformulate this sentence please to make it clearer?
Line 192: What do you mean with “early” in “…we note that the early QBO westerly…”
Line 197: “zonal mean impact“ what do you mean with “impact”?
Line 201: Are those responses due to the disruption or due to the QBO in general? I.e. Do the responses just follow the stratospheric wind regime no matter if there is a disruption or not?
Line 204: “below the altitude of 20 km”: at about 20 km there is the maximum hydration?! It is rather 18 km? You could add minor tick marks to the plot to see clearly where the sign changes.
Line 204ff: How can you be sure?
Line 209f: “but stronger in winter hemisphere” Do you mean “but more in the winter hemisphere” or “but is stronger in the winter hemisphere”?
Line 212: “consistent” Do you mean “correspond”?
Line 226: “particularly large“ please indicate what figures you are referring to.
Line 234: “induced secondary circulation are weaker” should I not see this in figure S4a,b?
Line 260: It is very difficult to follow your argument here, especially because the tropospheric w* differences look very strange. In your argument you don’t mention altitude ranges so which makes it difficult to follow.
Line 264: “(Fig. 4c in the supplement)” does not show cold point temperatures. What do you mean with substantially in “substantially negative”? Maybe better “strongly negative”?
Line 266 Figure 4 which you refer to does not show water or ozone? Neither does Figure S4?! Please correct.
Line 279 “hidding” should be “hiding”
Line 297 “net wave forcing is stronger and broader” do you mean the red region between 20 and 25 km altitude?
Line 298 “wave breaking near the equatorward” do you mean the blue region between 18 and 22 km between latitudes of about -20° and +17°?
Line 303ff: “The wave forcing evolution…” what do you mean? Adding the components gives you the total? I guess I misunderstand this sentence?
Line 322: What do you mean with “for the tropical upwelling of the BDC differences”?
Line 341: “few months after the sudden shift from the QBO westerly to QBO easterly wind shear reached the tropical tropopause. “ For ozone it seems to have happened already earlier!
Line 349ff: How can you be sure of this statement? (“strengthening of the tropical upwelling of the BDC”)
Line 362 “warmed the cold point temperature” should be “raised the cold point temperature”
In the Figure captions you repeat the definitions for a, b, c etc very often. It would be good to remove the repetitions.
Figure 1: I would prefer omitting the first (a) and putting the ERA in the description under the second (a).
“50hPa” it would be good to have an approximate altitude at 50 hPa to see where we are in the panels (a) to (c).
The QBOi line looks weird because of the disruptions. Also here it would be good to see how regular it looked before. Please add months as minor tick marks.
Figure 4: The labeling seems wrong in the first sentence. What you call b should be c and vice versa. What you call “impact” I presume comes from the multiple regression analysis?
Figure S1: The altitudes in the text refer to pressure altitudes whereas here are only altitudes in km. Please make consistent. The whole year average for Figures a) and b) depends a lot on the phase of the QBO for that year.
It appears that Figure S3 is mentioned before Figure S2 in the text, please reverse order.
Figure S2: There is a mistake: instead of 2016 (a, c) and 2020 (b, *c*) it should be 2016 (a, c) and 2020 (b, *d*).
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RC3: 'Comment on acp-2022-382', Anonymous Referee #3, 30 Jun 2022
Diallo et al. present results from a multiple regression analysis of water vapor and ozone data from MLS and wind and temperature fields from ERA50 spanning 2013–2020 to delineate the impacts of QBO from other natural variations (e.g. El Niño) and from time-varying forcings (i.e. aerosol optical depth). They find distinct planetary wave forcing patterns corresponding to each of the two QBO disruptions, and ascribe the anomalously moist lower stratosphere during the 2020 disruption to Australian wildfires.
I have concerns about the robustness of the multiple linear regression and the statistical methods used on such a short time series. I think the paper itself could use editing for flow, clarity, and language. The figures show much more information than is actually discussed, making it a chore for the reader to discern the meaningful results.
Significance: Good (3) understanding the impact of QBO disruptions is helpful, particularly inasmuch as their frequency may increase in the immediate future.
Scientific Quality: Fair (2) The authors are abreast of recent literature, but I’m not convinced the methods are adequate to produce meaningfully significant results.
Presentation Quality: Poor (1) There is a lot of information shown in the figures, which all use the same color scales and are not prominently labeled. It takes a considerable amount of effort for the reader to distill the important information from the figures, and the language and writing in the paper make it more difficult.- Does the paper address relevant scientific questions within the scope of ACP?
Yes. The objective of this paper is important and germane to ACP. - Does the paper present novel concepts, ideas, tools, or data?
Yes. The multiple regression analysis including both the recent QBO disruptions is timely and useful. - Are substantial conclusions reached?
I think so; the location of the eddy forcing is helpful to know, and the attribution of moist UTLS during the 2020 disruption to the Australian wildfires – an impact that has been discussed in the community – is important to show. - Are the scientific methods and assumptions valid and clearly outlined?
I don’t believe they are clearly outlined. I think the multiple regression analysis on 8 years of data – dealing with oscillations that are subseasonal-to-nearly-interdecadal in scope – may be over-determined. Furthermore, while the authors state that a t-test is used to test for statistical significance, they do not specify the parameters used (e.g., the effective degrees of freedom, which I believe to be important in a time series that is temporally over-sampled with respect to the QBO, ENSO, etc.). - Are the results sufficient to support the interpretations and conclusions?
I don’t believe so. Again, I think – considering the shortness of the MLS record – that the multiple regression analysis used here is likely to appear more significant than it is. Also, there is an implicit assumption in the test that the QBO disruptions are well described by a one-dimensional QBO index time series. In other words, that the impacts of the QBO are the same as the impacts of any other transition between QBO phases with a similar index. If this is indeed the case, the QBO disruptions may not be so interesting. If this is not the case, then the interesting impacts of QBO disruptions seem more likely to appear in the residual term (epsilon), but this is not examined in detail. - Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results)?
I don’t believe so, for reasons stated above. Also, Figure 3E is said to capture the aerosol optical depth (AOD) impacts of the Australian wildfires, but since there are only two disruptions, of differing character, it seems possible that some of the impact of the QBO disruption itself may be wrapped up in the AOD term, in addition to the residual term. - Do the authors give proper credit to related work and clearly indicate their own new/original contribution?
I believe so. The authors cite a good variety of work, including very recent work, and the authors’ own related contributions. It seems strange to me that Taguchi (2010) is being cited to back up the statement that there is not yet a clear understanding of how QBO disruptions are linked to anomalous sea surface temperatures, since QBO disruptions had never occurred when that paper was written. - Does the title clearly reflect the contents of the paper?
Yes. - Does the abstract provide a concise and complete summary?
Yes - Is the overall presentation well structured and clear?
The paper could use some work in this regard. Paragraphs are rambling, having at times several different subjects. There are no subsections to aid quick navigation of the paper. - Is the language fluent and precise?
The paper needs editing to be publication ready. Like the paragraphs, the sentences are long and often have weak structure. Definite/indefinite articles are often missing, singular/plural disagreement is prominent. Many other phrases (e.g. “the quasi-periodic QBO cycle of about 28–month period” on line 37) are just a bit awkward and could use careful reading by a native English speaker. - Are mathematical formulae, symbols, abbreviations, and units correctly defined and used?
Yes. - Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?
I think many of the figures show 2D anomalies, but only certain levels or time periods are described. Perhaps reducing the dimensionality of the figures would make the authors’ message clearer.
Figure production is rough, with uniformly small labeling for ticks labels, and figure panel titles. The figure lettering is added after the fact, is large, and is removed from the figure panel title. Some figure labels are missing. All color scales are the same. - Is the amount and quality of supplementary material appropriate?
I think the supplementary figures are of similarly rough quality to the figures in the main text. The figures I would be most interested in (some of the other regression terms) are not shown.
A few small edits/suggestions follow:
- Line 7: “circulation anomalous responses” needs re-wording
- Lines 9–11: this sentence needs to be split or otherwise clarified.
- Line 31: “Considered as a…” could just be “Considered a…”
- Line 37: “The quasi-periodic QBO cycle of about 28–month period” needs rewording
- Line 44: “study” should be “studies”
- Line 50: comma needed after amplitude.
- Line 74: “planetary (PWD) and gravity (GWD) wave drag” would be better as “planetary wave drag (PWD) and gravity wave drag (GWD).” It’s just two words more, but much easier to read.
- Line 99: “In in”
- Lines 104–106: Sentence beginning with “Both” is then used to contrast the two QBO events. Re-word.
- Lines 161–163: This sentence is confusing. I keep reading “fits” as a verb, and it breaks everything. Make it clear.
- Lines 148–164: This paragraph doesn’t have a clear direction/subject to me.
- Lines 282–285: The last sentence of the previous paragraph and the first sentence of the subsequent paragraph are a bit redundant—they both serve to introduce the topic of gravity wave drag
- Line 327: The word “finally” is repeated. Check how many times it’s used. Use it once.
- Does the paper address relevant scientific questions within the scope of ACP?
Mohamadou A. Diallo et al.
Mohamadou A. Diallo et al.
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