Generally, the structure of the main text is quite good. The storyline through the sections and subsections appears logical, the main findings are nicely summarized in Section 7, and some lengthy “side excursions” have been removed.

However, the paper is still moving on the edge of being “information overload”, especially with the large amount of cross referencing to the Appendices and Supplement. Some of this extra material is important and well justified, but in some cases, I’m not sure if it is really necessary and if the placement in an Appendix/Supplement is the correct choice. Please consider the following specific remarks and suggestions in that respect:

Appendix A: from the title of the Appendix, this is not different from Section 6.1, and some of the extra discussion of processing inside the ASMA could be blended into that Section in the main text. But much of the material, such as the comparison to CARIBIC and Satellite observations and the model sensitivity studies seem more appropriate in the supplement (some of the figures are already there, e.g. Figure S10) to convince those readers who have doubts about the model lighting NOx.

Appendix B: I think this could be shortened a bit and added to the main text. Figures B1 and B3 can be added to Figures 4 and 3, and the discussion added to Sections 4, 5 and 6, maybe by adding subsections. I don’t see that NOy is so much less important than the other material discussed in the main text, and I don’t think it will disrupt the main text too much. You mention all tracer-tracer relations in the first sentence of Section 4.1 and state that some are shown in that Section and others in the Appendix. But a reasoning why the NOx relations are not discussed in the main text is not given.

Appendix C: does this “primer” contain any information that is not available in the literature? I don’t think it is really needed and suggest referring to one or a few papers (or even books) where tracer relations are introduced in some detail.

With respect to the supplementary figures, some of them are referred to and discussed in the main text in just the same way as normal figures (e.g. page 11, line 26, page 15, line 20, and quite a few others), and I don’t see any harm including some of them in the main part of the paper. Extra figures typically don’t disrupt the story line, and there is not an official limit with respect to the number of Figures in a paper. I’m thinking that especially Figures S1, S11 and S16 would be nice to have in the main part of the paper: they are very interesting and highly relevant and do not just provide extra documentation and reproducibility. For the multi-year information, data comparisons and model sensitivities, these are indeed appropriately placed in the supplement if you do want to show all of them. Maybe you can add a bit of discussion in the actual supplement, e.g. move some of the material from Appendix A into the supplement, so it becomes a little more independent and rounds up all “extra topics”. In fact, you may want to consider giving the supplement a bit of structure, e.g. model comparison to satellite data, inter-annual variability, process sensitivities in the model. In that case, the referencing in the main text to this “extra material” becomes much clearer.


Besides considering the suggested rearrangements into main text and supplements, the following technical corrections need to be made prior to final publication:

The in-text referencing of the figures is not in the correct order (e.g. Figure 2 should be referred to earlier than Figure 7). In particular, Figures discussed in detail later are referred to in quite random order in Section 3. Please either renumber your figures, or adjust the text so that the referring is in the correct order.

On the same note, Section 5 discusses in detail what is seen in Figure 4, but the subsections 5.1 to 5.4 correspond to e/f, c/d, a/b and g/h respectively. I suggest changing the order of the gases shown in the Figure according to the Section ordering, i.e. O3 on top, then CO, then HCl and then NOx.

Page 6, line 4: I don’t understand the word “enhanced” here. If you refer to the vertical gradients in O3 itself, then please delete “Enhanced”. If you mean something else, then please explain.

Page 6, lines 13 and 16: please add some literature references that HCl is a good tracer for stratospheric O3 entrainments and that daytime NO is a good proxy for NOx.

Page 9, line 20: the circled area looks more like 300 to 500 hPa below the TP rather than 200 to 300 hPa. Please check this and correct or clarify!

Page 13, line 14: should be (“2” in Fig. 6) instead of (“2” in Fig. 4)

Caption Figure 3: it should be (b,e) and (c/f) in lines 4 and 6

Caption Figure 4: please remove the #+ in front of the Figure numbering

Caption Figure 6, line 9: between 200 and 700 ppb NOx seems incredibly high. Please check and correct this!

Dear Authors,

I think that the manuscript has been further improved and the structure is much more helpful now. Thanks for putting this effort into it! I hereby accept your manuscript for publication in ACP.

Best regards,
Marc