Dynamical and surface impacts of the January 2021  sudden stratospheric warming in novel Aeolus  wind observations, MLS and ERA5

Wright, Corwin J.; Hall, Richard J.; Banyard, Timothy P.; Hindley, Neil P.; Krisch, Isabell; Mitchell, Daniel M.; Seviour, William J. M.

doi:https://doi.org/10.5194/wcd-2-1283-2021

Articles | Volume 2, issue 4

https://doi.org/10.5194/wcd-2-1283-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Aeolus data and their application (AMT/ACP/WCD inter-journal...

https://doi.org/10.5194/wcd-2-1283-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 2, issue 4

Research article

|

20 Dec 2021

Research article |

| 20 Dec 2021

Dynamical and surface impacts of the January 2021 sudden stratospheric warming in novel Aeolus wind observations, MLS and ERA5

Corwin J. Wright, Richard J. Hall, Timothy P. Banyard, Neil P. Hindley, Isabell Krisch, Daniel M. Mitchell, and William J. M. Seviour

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Final revised paper (published on 20 Dec 2021)
Supplement to the final revised paper
Preprint (discussion started on 30 Mar 2021)
Supplement to the preprint

Interactive discussion

Status: closed

RC1: 'Comment on wcd-2021-16', Gloria Manney, 03 May 2021

Please see accompanying PDF file.

Citation: https://doi.org/10.5194/wcd-2021-16-RC1
RC2:
'Comment on wcd-2021-16', Isabell Krisch, 04 May 2021
The provided manuscript of Wright et al. on “Dynamical and Surface Impacts of the January 2021 Sudden Stratospheric Warming in Novel Aeolus Wind Observations, MLS and ERA5” is a very extensive analysis which is overall well written. It contains a very detailed overview over the most recent SSW including all necessary details on the formation and impacts. In contrast to many other studies, Wright et al. focus on the use of measurement data and mostly only use model (reanalysis) data to complement and support the conclusions. The newly available wind data from the Aeolus satellite provide new possibilities for the analysis of SSWs which is nicely demonstrated by this paper.

However, there are three major points which I would propose to improve before publication:

The two different objectives of this paper make it sometimes difficult to read. The authors should therefore revise the manuscript and think about possible ways of restructuring to make it easier to read.

The use of measurement data where possible is a large asset of this paper. However, this is not fully consistent throughout the paper. At many locations I would recommend to use MLS data (GPH and/or geostrophic wind) instead of ERA5 reanalysis data. More details on this are given below.

The calculation of the Aeolus projected zonal and meridional winds (which is in detail described in the appendix) should be revisited. More details can be found in the comments to the appendix.

More detailed comments are given below.

A paper on SSWs should probably include a reference to the most recent review on this topic, Baldwin et al. 2020 (e.g. to be added in line 35).

L1-4: Major SSWs lead to a reversal of the wind. For SSWs in general (minor + major) the given definition is correct. The rise happens over just a few days, but has to remain reversed for a longer period. Maybe revise this sentence.

L5-7: Sentence itself is correct, but might be misleading as multiple other missions measuring temperature also provide wind products (even though not direct). This point is nicely explained in the introduction, but should also become clear in the abstract.

L9-10: As you notice correctly in the introduction, already in Jan 2019 a major SSW was observed by Aeolus. Additionally, in Sep 2019 a minor SSW was observed over Antarctica. The data from Jan 2019 is reliable, but not yet available for scientific analysis due to large systematic biases. These biases need to be removed by reprocessing before the data can be used for scientific analysis. The reprocessing is planned for end-2021.

L17-18: Does this paper really show 3)?

L69: Maybe include Stoffelen et al 2020 here.

L73/74: Are there no newer publications on ALADIN? 1989 is 30 years before launch!

L76: vertical resolution is ~0.5-2km (0.5km is rare nowadays)

L77: The hot pixel correction is described in Weiler et al 2020

L78: Rennie and Isaksen 2020 could be updated to Michael Rennie, Lars Isaksen, Fabian Weiler, Jos de Kloe, Thomas Kanitz, Oliver Reitebuch: The impact of Aeolus wind retrievals in ECMWF global weather forecasts, QJRMS, 2021 (if this becomes available in time; the revised version was submitted recently and publication is expected soon).

L90-94: As Aeolus data is one of the major components of this paper, I would propose to explain the vertical sampling of Aeolus a bit more in detail. First, the vertical sampling changes in height (maybe even include typical altitude profiles), then in location (the range bin settings are terrain following and change e.g. at 60°N), and last but not least also in time (however, this should not be the case throughout your study period). Especially the change at 60°N is worthwhile mentioning as this impacts all your estimates (means). Thus, I recommend plotting two sampling profiles at >60°N and <60°N to explain this change.

L69-94: The following information is missing here and should be added for clarity: Aeolus horizontal resolution, which data (baseline) was used, and which quality filtering has been applied.

L102: Here you give precision, whereas for Aeolus you state the systematic bias (accuracy). As your analysis uses mean values, the precision of MLS is probably not representative for your data and the accuracy should be given instead.

L130: Is MLS assimilated in ERA5/OPAl?

L145-151: This approach is a good idea!

Figure 1 and others: Are you sure the differences at 22km are not due to the Aeolus sampling (only data available >60°N -> data plotted is for 62.5°N, not for 60°N). You should verify that the averaged latitude is consistent for the different datasets.

Figure 1: Interesting, that just before the SSW onset (day 0), Aeolus shows weaker winds than ERA5 at 22km whereas stronger winds at 15km.

L162: many previous studies (even though they are by Manney et al.)

L170/171: The paper is long enough as is, thus, I understand the authors here. Still for such a new dataset as Aeolus closer investigations of the differences at geographical scale could probably raise the confidence in the projected meridional winds.

L173/174: Please see comment above.

L173-177: From my point of view, this paragraph is not really necessary, wrong (reliability of Aeolus data) and could be removed completely.

Figure 2: To be consistent with Figure 1: Why not use similar or even the same altitude levels? Especially, why not show 10hPa (32km) as this altitude is used for the main definition of SSWs?

L187/188: Maybe citation of a 2017 paper not correct for 2 events out of which one is from 2019?

L214: mission-to-date day-of-year median: Is this for the time period 2004-2021?

L220: Also validation campaigns do not show a strong altitude dependence of the bias and reasonable values down to 2km (e.g. Witschas et al 2020, Lux et al 2020)

Figure 4: Again, I am not sure if an average around 60°N is recommendable for Aeolus data above ~17km as this might actually be the average at 62.5km. This sampling bias should be investigated and discussed in the paper. For validation of Aeolus winds, it would be good to include MLS winds in this plot as well.

Figure 3 & 4: I would somehow propose to combine these two Figures or put them close too each other as otherwise the reader is constantly going back and forth.

Figure 5: Before only measurement data (MLS & Aeolus) was used. Why introducing here ERA5 if MLS GPH data is available? What is the additional information or do MLS and ERA5 differ significantly?

L323/324: Citing from Baldwin et al. 2020 (link provided above): “About a third of the observed 36 major SSWs in the 1958–2012 period can be unambiguously classified across all methods as splits and another third as displacements (Gerber et al., 2021). The rest of the events are more ambiguous across methods, perhaps because in some cases, the polar vortex both displaces and splits within a period of several days (Rao et al., 2019).” Thus, the 2021 event just seems to fall in the third category.

L330-332: I am not sure, I fully understand this sentence. Could you maybe rephrase it?

Figure 6: For analysis of SSW, I would include 10hPa. This should be possible by using MLS meridional winds. Also, for lower altitudes, it might be valuable to compare data using only MLS (u, v, T), MLS T + Aeolus (u, v), MLS (T, v) + Aeolus u, and reanalysis and hybrid as plotted. For a consistent use of the combination of Aeolus winds with an external v (ERA5 or MLS), the external v should already be used when converting HLOS to u. Maybe also think about using some kind of “apriori” u and v values for the conversion of HLOS to v and u, respectively. For this topic, please also see my comments to the appendix.

L363: Are the mentioned sampling pattern issues by any chance related to the use of different numbers of ascending and descending orbits? For details see my comments to the appendix.

L374: If this is a real difference should be easy to check by using an apriori u from either MLS or ERA5 when deriving v from HLOS. See comments to appendix.

L377: “note the different vertical scales” can be mentioned here, but definitely belongs to the figure caption.

L425-427: When averaging over Aeolus data you should definitely pay attention that ascending and descending orbits contribute evenly as then the errors due to u (or v) better cancel out. See comments to the appendix.

L440: Why again using ERA5 instead of MLS?

L464/465: Is there already “typical” Aeolus winter data?

Figure 9: Again, why not use MLS? Does MLS give significant different results or is the data too coarse?

Sections 7.1 and 7.2 are somewhat repetitive. Maybe they could be joined and all Figures could be discussed simultaneously?

Line 532: units not consistent between text and figure.

Line 539-540: Can MLS winds provide this missing information?

L 563: 85°N

L639: Referring back to my citation of Baldwin et al 2020: 1/3 of all SSWs are not easily classifiable. Thus, better remove “unlike many others”.

L644: For clarity add 60°*N*.

L670: “timing” double

L670: Is there a way to asses if this is really a timing effect or an offset effect?

Appendix:

General comment: This appendix is very interesting and important to interpret the Aeolus data quality. However, I would propose to include the different orbit geometry for ascending and descending orbits as described in the following. Regarding the formulas, I am not 100% sure what the authors have done in equations (A2) & (A3). To my understanding, converting HLOS to u_HLOS (and neglecting the v_HLOS contribution) should lead to HLOS/sinθ (not HLOS * sinθ, as given in A2). Same for v_HLOS in A3, btw. If I now follow these corrected equations, I get to a zonal wind error (u_HLOS – u) of v/tanθ (or -v/tanθ depending on the definition of θ). This has opposite sign (for same/similar v) for ascending and descending orbits. Thus, averaging u_HLOS over the same amount of ascending and descending orbits should remove this error almost completely, but not if one considers only ascending or only descending orbits.

In a similar way, one should be able to construct a more or less reliable meridional wind by first averaging over HLOS for both ascending and descending orbits (u * sinθ part cancels out) and then dividing by cosθ.

Additionally, two minor comments to this appendix:

L704: Why do you use January 2020 data even though your paper mainly treats January 2021 data?

Figure A2: Which binning is used here?

References:

Baldwin, M. P., Ayarzagüena, B., Birner, T., Butchart, N., Butler, A. H., Charlton-Perez, A. J., et al. (2021). Sudden stratospheric warmings. Reviews of Geophysics, 59, e2020RG000708. https://doi.org/10.1029/2020RG000708

Stoffelen, A., Benedetti, A., Borde, R., Dabas, A., Flamant, P., Forsythe, M., Hardesty, M., Isaksen, L., Källén, E., Körnich, H., Lee, T., Reitebuch, O., Rennie, M., Riishøjgaard, L., Schyberg, H., Straume, A. G., & Vaughan, M. (2020). Wind Profile Satellite Observation Requirements and Capabilities, Bulletin of the American Meteorological Society, 101(11), E2005-E2021. Retrieved May 4, 2021, from https://journals.ametsoc.org/view/journals/bams/101/11/bamsD180202.xml

Weiler, F., Kanitz, T., Wernham, D., Rennie, M., Huber, D., Schillinger, M., Saint-Pe, O., Bell, R., Parrinello, T., and Reitebuch, O.: Characterization of dark current signal measurements of the ACCDs used on-board the Aeolus satellite, Atmos. Meas. Tech. Discuss. [preprint], https://doi.org/10.5194/amt-2020-458, in review, 2020.

Witschas, B., Lemmerz, C., Geiß, A., Lux, O., Marksteiner, U., Rahm, S., Reitebuch, O., and Weiler, F.: First validation of Aeolus wind observations by airborne Doppler wind lidar measurements, Atmos. Meas. Tech., 13, 2381–2396, https://doi.org/10.5194/amt-13-2381-2020, 2020.

Lux, O., Lemmerz, C., Weiler, F., Marksteiner, U., Witschas, B., Rahm, S., Geiß, A., and Reitebuch, O.: Intercomparison of wind observations from the European Space Agency's Aeolus satellite mission and the ALADIN Airborne Demonstrator, Atmos. Meas. Tech., 13, 2075–2097, https://doi.org/10.5194/amt-13-2075-2020, 2020.
Citation: https://doi.org/10.5194/wcd-2021-16-RC2
EC1:
'Comment on wcd-2021-16', Peter Knippertz, 05 May 2021

First of all, I would like to thank the two reviewers for their excellent reviews. Second, I would like to invite the authors to reply to the general suggestions by the two reviewers to split or significantly shorten the material. I feel that we need a top-level agreement on this before spending any time on the details of the science.

Citation: https://doi.org/10.5194/wcd-2021-16-EC1
- CC1: 'Reply on EC1', Corwin Wright, 05 May 2021
  
  Dear Peter et al,
  I agree that a decision is needed on whether or not to split the paper before we proceed further with the review. We will consider this carefully, and I will provide a more detailed response to this question by the end of the week at the latest (i.e. within two to three days).
  Corwin
  (submitting as a Community Comment rather than an Author Comment as I have not yet discussed this with the co-authors)
  
  Citation: https://doi.org/10.5194/wcd-2021-16-CC1
- AC1:
  'Reply on EC1', Corwin Wright, 07 May 2021
  
  Dear all,
  I have now had chance to discuss it with co-authors. Apologies for the short delay while I did so.
  First, while I only address top-level structure in this response, I should make clear that I have read and acknowledge all the specific comments provided by Drs Krisch and Manney, and greatly appreciate the significant time they have spent on their reviews. Most of the changes requested are excellent suggestions that will significantly strengthen the manuscipt when implemented. I hope to respond to each comment individually and in detail at a later date.
  In the remainder of this Comment, I will address only the top-level debate on which Dr Knippertz has requested a speedy response. I will first summarise my interpretation of the two suggested approaches, and then respond to them both in combination.
  Dr Manney has suggested taking the material from the existing manuscript and splitting it into two manuscripts, which I will term Manuscripts 1 and 2. Manuscript 1 would be focused primarily on validation of how Aeolus represents extreme events such as SSWs, and Manuscript 2 would use reanalysis data only to study the 2021 SSW.
  Dr Krisch instead suggests a different approach, which I will term Manuscript 3. This manuscript would be broadly similar in conception to the current manuscript, but would be simplified in structure, and use more observational data and less reanalysis data (specifically switching ERA5 GPH for MLS GPH), and better describe the calculation of the Aeolus winds.
  In general, my intended conception of the current study (which my co-authors have supported in email discussion) is very significantly closer to Manuscript 3 than to Manuscripts 1 and 2, but I agree that the work presented could be sensibly modified to separate out the material for a separate Manuscript 1. In line with this conceptual model, I propose the following approach:
  ----
  
  A. The current manuscript would be transformed into something close to Manuscript 3, as follows:
  Aa. remove both appendices, adding a concise section of text which more carefully explains the method used to project the winds.
  Ab. remove the current Section 6 ("Mesoscale forcing").
  Ac. remove all text describing results from these sections from the introduction, conclusions and other sections
  Ad. restructure and reorder the text to provide a clearer flow.
  Ae. investigate the possibility of using MLS GPH data instead of ERA5 data. This could work well for Figure 9, which is stratosphere-only, but may not be a viable approach for Figure 10 as this which relies on reanalysis output below the bottom of the MLS scan. A hybrid approach may be possible here using MLS GPH in the upper part and ERA5 below with the cutoff between the two clearly indicated, and I can investigate this, but there may be more benefit to using the same product across the full height range, even if this leads to a slight disjoint with Figure 9.
  --
  
  B. The validation and methodological material would be removed to a new manuscript, to be submitted in principle to Atmos. Meas. Tech. or a similar journal. This manuscript would contain:
  Ba. an extended form of Appendix 1, including a new section showing the benefits and disbenefits of different methods of estimating u and v from Aeolus. Co-author Hindley and I have discussed the possible contents of such a section today. The assessment would be carried out for both 2020 and 2021, as the 2020 data should be out of embargo* soon.
  Bb. an extended form of Appendix 2, including spatial as well as zonal-mean comparisons.
  Bc. a detailed investigation of the 'lag' seen in Figure 1 between Aeolus and the reanalysis/analysis products, to investigate whether the differences are due to spatial sampling or a real lag in the assimilative systems.
  Bd. [perhaps] a modified version of the current Section 6.
  (* the seemingly-odd choice to test on 2020 was because I did not realise the 2020 data were still under embargo when carrying out the assessment - early drafts of the manuscript more logically included a full comparison to the preliminary 2020 observations!)
  --
  My estimate is that these changes would reduce the manuscript length by just over 10 preprint-format pages, i.e. approximately a third of the current manuscript length without references, and provide sufficient material for a second manuscript of roughly similar length and technical level to e.g. the currently under-review https://amt.copernicus.org/preprints/amt-2021-93/ . Such a split and rearrangement would address all the top-level concerns of Dr Krisch, and address one of the primary concerns of Dr Manney, specifically that the validation objectives of the paper do not mesh well with the science objectives.
  
  The key area in which Dr Manney's comments would not be addressed by this approach is that observational data would be retained for the current study, rather than switching to entirely reanalysis data for these objectives as she proposes. I strongly disagree with a change of this nature:
  1. I feel this suggestion may have arisen due to a possible large mismatch between authorial intent and reviewer interpretation of that intent, likely due to poor communication by myself when writing the introduction. Essentially, the manuscript Dr Manney is requesting describes a significantly different study to the work we have actually done and the manuscript we have set out to write. Due to this very significant mismatch, making such a change would, in practice, mean discarding all of the work carried out and starting again ab initio with only an outline structure and no scientific content, with the end result being a manuscript the authorial team never set out to write.
  2. More broadly, I feel it is important that we as a scientific community continue to carry out wholely-observational science to at least some degree, rather than switching to reanalysis for all dynamical studies of the lower and lower-middle atmosphere. Modern reanalyses are indeed excellent (I have lead- and coauthored several papers myself quantitatively demonstrating this!), but we know that they still have many important biases and inaccuracies, and this is doubly the case when looking at variables not assimilated into the models such as (for ERA5) observed winds.
  
  Citation: https://doi.org/10.5194/wcd-2021-16-AC1
  - RC3: 'Reply on AC1', Gloria Manney, 07 May 2021
    
    In light of the author's proposed path for splitting the paper, I had a chat with Michael Schwartz, who is the cognizent scientist for MLS temperature and GPH. With any version previous to v5 of MLS GPH, he (and therefore I) would have been uncomfortable with basing this kind of dynamical study on MLS GPH / temperature, and would have strongly recommended using the reanalysis data instead. MLS GPH, however, has been substantially improved in v5 such that Michael (and therefore I) would recommend it for this kind of use (though he does still opine that the reanalyses are probably better anywhere below about 10hPa or so, and that because the MLS GPH is built up from its temperatures, biases and oscillations in those are reflected in the GPH). Another important caveat is that a significant part of the improvement in MLS GPH in v5 was achieved by building it on top of the 100hPa GEOS5 analysis (very nearly identical to the MERRA2 reanalysis at this level, but available in NRT). Thus if joining to a reanalysis to get tropospheric fields, one should either (1) join to MERRA2, or (2) in order to appropriately "correct the origin", subtract off 100hPa GPH from the MLS GPH fields and add back in (point by point and time by time) the 100hPa (and use those below 100hPa) fields from the reanalysis used (presumably ERA5 if you don't want to use MERRA2).
    If this sort of approach was taken, I would in principle (obviously in practice and for specifics, one would have to see the revised paper(s)) support the approach the authors are proposing for revising the paper.
    
    Citation: https://doi.org/10.5194/wcd-2021-16-RC3
    
    EC2: 'Reply on RC3', Peter Knippertz, 11 May 2021
    
    First of all I would like to thank the authors for their thoughtful reply to the question on restructuring the work. I agree that the Manuscript 3 solution you outline looks like the best way forward and is still well within the scope of WCD.
    Secondly, I'd like to thank Gloria Manney for going the extra-mile and inquiring about the current state of the MLS data. Generally I would welcome the use of these data in addition to Aeolus but the caveats outlined by Gloria need to be clearly articulated in the paper.
    So in conclusion, please go ahead and start the revision based on your Manuscript 3 concept.
    
    Citation: https://doi.org/10.5194/wcd-2021-16-EC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Corwin Wright on behalf of the Authors (20 Aug 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to revisions (further review by editor and referees) (05 Sep 2021) by Peter Knippertz

ED: Referee Nomination & Report Request started (13 Sep 2021) by Peter Knippertz

RR by Gloria Manney (15 Oct 2021)

For final publication, the manuscript should be

accepted as is

accepted subject to technical corrections

accepted subject to minor revisions

reconsidered after major revisions

rejected

Were a revised manuscript to be sent for another round of reviews:

I would be willing to review the revised manuscript.

I would not be willing to review the revised manuscript.

Suggestions for revision or reasons for rejection

Reevaluation of “Dynamical and Surface Impacts of the January 2021 Sudden Stratospheric Warming in Novel Aeolus Wind Observations, MLS and ERA5”, Wright et al.
(Reviewed by Gloria L Manney)

Recommendation: Accept after some minor revisions, clarifications, and corrections

General Comments: This paper is substantially improved over the original submission. I still find it rather unfocused (and thus somewhat difficult to read) because of the number of topics with different foci that the authors are bringing together, but the science is sound and interesting, and is now largely well-presented; thus I think it is ultimately suitable for publication in WCD. There are, however, a number of small points that are either unclear or incomplete, several places where important references are left out, and many typos, small grammatical errors, and style “choices” that hinder clarity; these should be addressed before the paper is ready for publication.

Most of my comments are given as pop-up notes in the tracked changes version of the MS, which is uploaded with this review at the "referee report". I hope this does not make it awkward, but it would have taken much more time to transcribe them with their associated location information, and many of them are small typos or wording issues for which I believe it’s more efficient for everyone to see marked in the manuscript. A few additional thoughts:

I still believe that the motivation / reasoning for the choice of datasets used (specifically, why you want to use MLS rather than ERA5 for most of the “dynamical context” material) should be stated -- it is a choice, both datasets are of a quality that supports the analysis you are doing -- but I think most readers would like a brief statement (perhaps in the second to last paragraph of the introduction where you list the datasets you are using) of your reasons/philosophy in making that choice.

While the 3D images in Figure 8 are improved over the versions in the original manuscript, they are still difficult to get much information out of and to see the (few) features that are pointed out in the text. While I don’t insist that it be deleted, IMO this figure (and the corresponding supplementary figure, which should be updated with the same format changes as Figure 8 if retained) is unnecessary.

Per the query in the author’s responses, the Smith et al (2019) paper mentioned in my original review is https://doi.org/10.1002/qj.3690.

Grammar and/or Style that substantially impairs clarity:

The use of the serial (aka “Oxford”) comma is rarely (never IMO) optional to achieve clarity. For example, the title of this paper without it can correctly be read to state that “MLS and ERA5” are “Novel Aeolus Wind Observations”; while it is highly unlikely that the intended audience for this paper would read it that way, that is not a good reason to be unclear/imprecise. Another example early in the paper is around line 40 (in the tracked changes version), “...models, reanalyses and winds inferred from gradients in other…” -- this could very easily (and grammatically correctly) be read as meaning both “reanalyses” and “winds” are “inferred from gradients…” -- someone in your intended audience who doesn’t happen to work with reanalyses and thus is not that familiar with them might plausibly make that mistake. There are more such cases in the paper, some of which make one have to pause to figure out what you really mean. I have marked missing Oxford commas in the manuscript, and adding these is really not optional for achieving clarity.

There are also some instances marked in the manuscript of using “due to” where what you mean is “because of” (along with numerous instances where you use it correctly), and where “which” rather than “that” is used for a restrictive clause. I have marked several of these again, because they do (especially in the latter case) significantly affect the clarity of the writing.
--------------------------------------------------------------------------------------------

An aside -- reply to an author response that doesn’t affect the paper:

Regarding: (My comment) 55. Section 8, Overall: To read and try to understand this section, the reader is constantly flipping back to virtually all of the previous time series figures in the paper. For this material to be communicated effectively, all of these figures should be introduced and discussed consecutively, and combined into as few separate figures as possible so that flipping back and forth and trying to eyeball lining up times is not constantly disrupting the flow of the narrative. It would also be much better focused if you weren’t constantly referring tto one quantity from one dataset and another from another, leaving the reader to wonder how much it matters which dataset you show (e.g., around lines 579–580). This sort of reorganization would vastly improve the paper, and would be straightforward to do if the Aeolus results were separated out into a different paper.
(Author response) I (Wright) disagree with the core argument here - perhaps due to misinterpretation of the written comment, or perhaps due to philosophical differences in our views on technical writing. Back- and cross-referencing are entirely normal parts of scientific (and general) writing; the sections are not intended to stand completely independently, and doing so would force an extremely artificial and narrow scope on both each individual section and on the manuscript as a whole.

My response: While the point is moot with respect to this paper because the reorganization and deletion of some material in the revised paper have resulted in greatly alleviating this issue (and thus making the paper much easier to follow), since the author (Wright) suggested he possibly misinterpreted my comment and indeed appears to have partially done so (so this is a comment to the authors for clarification, not something to change in the revised paper): In my professional experience, including teaching research and technical communications / writing to physics graduate students, I have always been taught (and have taught) that it is critical to make it as easy as possible for the reader to understand the points being made with the figures. Never had I seen anything that suggests that it is OK to separate figure panels that are much more easily interpreted in a certain orientation with respect to each other by many pages (in this case, time series for which the original manuscript described features that required lining up dates in multiple (more than two) figures, which would have been much clearer if the panels to be compared were arranged in a column so that the time axes are lined up). Neither have I ever heard any suggestion against introducing a figure with multiple panels when the first panel is discussed and then discussing succeeding panels later, even much later, in the text. Thus I was making no suggestion that sections should be independent or that back- or cross-referencing was a problem -- only that when it is feasible to arrange figure panels so as to make the relationships described immediately apparent (this was entirely feasible in the original manuscript) that should be done.

Referee Report: PDF

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ED: Publish subject to minor revisions (review by editor) (17 Oct 2021) by Peter Knippertz

AR by Corwin Wright on behalf of the Authors (11 Nov 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (14 Nov 2021) by Peter Knippertz

AR by Corwin Wright on behalf of the Authors (18 Nov 2021) Manuscript

Short summary

Major sudden stratospheric warmings (SSWs) are some of the most dramatic events in the atmosphere and are believed to help cause extreme winter weather events such as the 2018 Beast from the East in Europe and North America. Here, we use unique data from the European Space Agency's new Aeolus satellite to make the first-ever measurements at a global scale of wind changes due to an SSW in the lower part of the atmosphere to help us understand how SSWs affect the atmosphere and surface weather.