|Second review of "Comparison of ozone profiles and influences from the tertiary ozone maximum in the night-to-day ratio above Switzerland" by Moreira and colleagues.|
The authors have dealt with the comments from me and the other reviewers well. The updated manuscript is better and, I think, largely suitable for publication in ACP. There are a few points where I think some minor updates or corrections are needed, these are noted below.
I do feel this paper still leaves the reader unclear about the implications of the 40% MLS/GROMOS difference in daytime mesospheric ozone. While some discussion has been added in section 4, it is still rather unclear (to me at least), what the authors are concluding from the observed discrepancy. See the specific points below.
This paper remains in the "grey zone" between ACP and AMT, but, particularly in the context of an NDACC special issue, I'm perfectly happy to see it published in the former.
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Line 10: Perhaps summarize the discussion I'm going to suggest you add in section 4 here (just a sentence or so if space).
Line 18: What sets the 1-hour temporal resolution? Presumably it's arbitrary, simply a case of whether you choose to average in spectral or geophysical space. Perhaps reword along those lines, stating that 1-hour was (presumably) chosen as it represented the finest temporal resolution that provided sufficiently noise-free measurements to be geophysically useful.
Lines 22-24: Awkward wording, suggest: "Changes in the stratospheric ozone concentration alter the radiative balance, composition, and dynamics of the atmosphere."
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Line 7: I'm glad the authors opted to follow my suggestion of including reactions. However, they seem to have done so in rather a strange manner, not least because they are introduced out of order. My suggestion would be to quote each reaction individually (or in small groups as needed) immediately as they are introduced. Lumping them all together (while appropriate for a figure/table) doesn't feel right for a set of reactions to me. I would simply think of them as "in line" entities rather than "floats".
Line 13: Suggest: "... summertime. The winter nighttime maximum is related to the ..."
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Line 5: 100hPa already feels pretty much like the "lower stratosphere" to me. Could you be clearer, was the 28% value chosen to be at some particular (larger) pressure level, or was it dictated by the time-dependent altitude of the tropopause?
Line 14: I would use the word "precision" rather than resolution. To me resolution risks being confused with spectral resolution.
Also, you haven't defined T_rec, and I (again) say it would not hurt at all to give us that number (I know it's in the 2015 reference, but it's a useful detail).
Line 17: I think this is unclear and risks confusing the reader. Is the (0.5K to "a few K") change in noise across the spectral line due to changes in Tb? Presumably not as Trec dominates and the Tb change would not give the 0.5 to a few K change. Presumably it's because of using a spectrometer (at least for the early part of the measurement record) that has channels that are narrower near the line center. The way it's written now, it sound like the signals are inherently noisier (per unit frequency) near the line center which (Tb issues aside) is not really the case, unless I've misunderstood things.
Line 22: Suggest simply: "Figure 1 compares version 2021 and ..."
Line 30: Suggest "version 150 appear in the" -> "version 150 are largest in the "
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Line 14: "We assume" sounds weak and is asking for a reviewer/reader to challenge you to prove it. You should give a more confident statement and say something like "Improvements in the retrieved product have resulted from a combination of changes in the a priori covariance, improved handling of measurement noise and changes to integration time".
Line 24: Froidevaux et al. 2009 (10.1029/2007JD008771) is the most suitable reference for MLS ozone validation. The Schwartz et al. paper describes the temperature and GPH products. I believe there is also an updated version of the Livesey et al. document (2017).
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Lines 17-20: I think the way this is worded it makes things sound much worse than they are. I would reword the final sentence of the paragraph ("We conclude...") along the lines of: "Overall, Figure 3 shows excellent (better than 5% [could be better, hard to tell from plot]) agreement between MLS and GROMOS over a large vertical range. Exceptions are in the lower stratosphere ..."
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Line 12/13: This sentence is awkwardly worded, and not just because of the parentheticals (see 10.1029/2010EO450004). I'd say: "We compute 'noon' and 'midnight' averages from the observations recorded over the 11AM/PM to 1PM/AM periods." or similar.
Line 23: This is unclear. Does "our results" refer to the GROMOS observations or to the results shown in the figures that indicate an MLS/GROMOS discrepancy? Either way, the sentence needs clarification. (See the note below concerning line 24 for a minor clarification needed). The main reason it needs clarification is that (to me) the logic doesn't flow. If, as I assume is the case, you mean "our results" to refer to the GROMOS measurements, then you've not explained why MLS might report the situation differently. Conversely, if "our results" are the discrepancy, then simply citing a gradient doesn't clarify the situation further. Are you saying that this difference is purely due to the horizontal gradients involved? A more quantitative discussion is needed in either case. As mentioned above, some brief summary of the points you make should be included in the abstract (page 1 line 10).
Line 24: For clarity I suggest: "... its effects extend from the polar regions into the midlatitudes with decreasing amplitude".
Line 27: "Planetary time scale" is odd wording to me. I understand planetary scale waves, but to me there is not an obvious time scale associated with "planetary" phenomena. Perhaps say "planetary wave time scale"?
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Line 3: Who is "we" in this context? GROMOS or Moreira et al using MLS and GROMOS data? Reword to clarify.
Line 13/14: Suggest you swap the order to: "Furthermore, we observe extensions of the middle mesospheric maximum of ozone (MMM) towards northern mid-latitudes during winter."
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Would be good to clarify whether it is the smoothed or "raw" MLS data used here. Presumably the smoothed, but it doesn't hurt to be explicit.