Second review of “Zonally asymmetric influences of the Quasi-Biennial Oscillation on stratospheric ozone” by Wang et al.
General comments
I understand that the authors made many efforts to improve the manuscript. Thank you for considering my comments and suggestions. However, I have still found a lot of errors, inconsistencies, typos, and insufficient explaining of logic in the revised manuscript; thus, I have several questions and comments (see the minor comments). I do not think the current version of the manuscript is acceptable as it is; the manuscript still seems to need corrections and refinements.
Major comments
First, I apologize to the authors for making comments and questions on points I did not mention in the original version. I have checked the manuscript more carefully in this round of review, and I have further comments and questions.
According to the description in the Method section (2.4), QBOW is a phase with westerly winds around 10 hPa. Is it correct? If so, for me, and possibly some others, who are used to the definition of QBO at 50 hPa, the relationship between the QBO phase and TCO anomaly sounds reversed and may be confusing. Would you add some descriptions explaining this? For example, “…during QBOW phases (easterly around 50 hPa), as compared with QBOE (westerly around 50 hPa).
The authors’ analyses were performed by evaluating the difference between the composites of QBOW and QBOE (QBOW–QBOE), and they gave descriptions like “Zonally asymmetric features are seen in the polar regions…”. I think they should state more clearly “zonally asymmetric features of the difference”. Making the difference between QBOW and QBOE is a standard practice to examine QBO effects, but my concern is that in Figs. 9, 10, 11, 12, and 13b, the contours are climatological means, while the colors are the difference between QBOW and QBOE. If the figures depicted the contours of QBOE means, I could easily understand how the QBOW changed the fields from QBOE; or if they used colors to show the difference between QBOW and the climatology along with the climatology contours, it would also be easy to understand the physical meaning. Do the authors assume that the climatology is near the mid-point between QBOW and QBOE?
In association with this, I am confused with the results shown in Fig. 12, although this figure seems to be interesting. The authors state that the QBO related wavenumber-1 anomalies (QBOW–QBOE) are generally out of phase with the climatological pattern. Therefore, in the QBOW phase, the zonal asymmetry is smaller and it is expected that wave activity is less than that in the QBOE. Is this correct? My understanding of E-P flux anomaly associated with the QBO phases is that more wave flux goes into the high latitude stratosphere when the tropical zonal wind around 50 hPa is easterly, thus polar vortex is weaker, and vice versa (less wave flux goes into the high latitude stratosphere when the tropical zonal wind around 50 hPa is westerly, thus polar vortex is stronger.) This relationship is the Holton and Tan relationship and several other works also showed this. I am wondering if the anomalies in Fig. 12 is consistent with the results from the preceding studies based on the zonal-mean zonal wind and E-P flux. Would you represent Fig. 12 by making difference between QBOW and climatology (QBOW–climatology) and between QBOE and climatology (QBOE–climatology), and depict the differences from by colors? Then you can check whether the anomaly distribution is “in-phase” or “out of phase” compared to the climatological mean geopotential height distribution for each QBO phase. I think that “out of phase” reduces the zonal asymmetry and corresponds to less E-P flux, then zonal winds in the tropics and 50 hPa should be westerly (QBOE in the author’s definition?).
An interesting point is the phase shift of the anomaly compared to the climatology in Fig. 12. This seems to be a new finding. I hope the authors represent this for the anomalies in the QBOW and QBOE phases separately with the climatology contours and discuss the reasons.
Another issue is that there are several sentences in which it is difficult to understand the logic or physical meaning. For example, the authors should carefully explain that the data period of TCO (1979–2020) and that of ozone at 10 hPa (2002–2020) is different when they compare between Figs.8 and 11.
Finally, I found an inconsistency in the figure format between Figs. 2, 3, 7, and 8 and Figs. 9–11
Minor comments
The line numbers refer to the ATC (article tracked changes) version.
1. Abstract: It would be better to include the period for analysis (1979–2020) somewhere. The ERA5 data have recently been updated for the period before 1979 due to some problems affecting the performance in the tropics in the original version. However, this would not affect the case under consideration, since the target period of this article is 1979–2020.
2. Abstract: An explanation of the QBO definition is needed, otherwise readers may be confused. See minor comment No.10.
3. Lines 17–18, “influenced by the corresponding temperature changes and subsequent chemical reactions”: It seems better to say, “influenced by chemical reactions associated with the corresponding temperature changes.”
4. Lines 29–30: Since the description associated with the references is a general description, add “e.g.,” before “Son et al., 2008….”, or add more appropriate references (review papers, for example).
5. Line 30, “WMO et al., 2018”: Should be “WMO 2018.”
6. Line 58: So, what is the level used to define the QBO?
7. Lines 64–65: I do not understand why the global pattern of ozone changes is important to the regional UV radiation. It is certain that regional ozone change is a cause of regional UV change.
8. Lines 65–66, “it is therefore interesting to look through the zonal differences of QBO signals in ozone”: I do not understand how this flows logically from the previous sentence.
9. Line 144, “deviation of the zonal mean”: Change to “deviation from the zonal mean”
10. Lines 148–149, “monthly anomalies of TCO near the equator (10S-10N) are anomalously high during QBOW phases compared with QBOE.”: This expression is understandable because the authors define QBO by PC1 (around 20 hPa). However, for me, and possibly some others, who are used to the definition of QBO at 50 hPa, the relationship between the QBO phase and TCO anomaly sounds reversed and may be confusing. Would you add some descriptions explaining this? For example, “…during QBOW phases (easterly around 50 hPa), as compared with QBOE (westerly around 50 hPa). I hope this kind of explanation may be repeated in other places where “QBOW” and “QBOE” appear in the text.
11. Line 156: Would you state here or somewhere that the anomaly distribution is the difference between QBOW and QBOE? The authors often mention a “zonally asymmetric feature” or “positive/negative anomaly is seen in …” in the text, but it is not compared to a climatological mean field but to the field in the QBOE.
12. Line 157, “to our understanding”: Change to “to the best of our knowledge.”
13. Line 164: Add “(Fig. 2d)” after “the QBO signals disappear in the NOQBO run”
14. Lines 164–165: I do not understand this sentence. My understanding is “Because the only difference between the two model simulations is the QBO nudging and because the difference in the two composites is similar between the simulation and the observation, this result indicates that the differences in the two composites of the observed TCO are mostly due to QBO.”
15. Line 181, “disappear”: The phrase “not evident” would be better.
16. Line 195, “in the stratosphere Fig. 4d”: Do you mean “in the stratosphere in Fig. 4d”?
17. Line 196, “sown”: Typo.
18. Lines 196–198 and Fig. 5: Can you say this without statistical significance in the positive anomalies in the lower and middle stratosphere? The authors could use the 90% level figure in the previous version and explain the relatively low significance for the seasonal panels.
19. Line 208, “SOLOMON et al.”: Should be “Solomon et al.”
20. Line 217, “to our understanding”: Change to “to the best of our knowledge.”
21. Lines 219–221: Fig. 7 indicates the distribution of QBOW–QBOE. The asymmetry during QBOE is not mentioned.
22. Lines 259–261: I think the authors should say, “The results are consistent with preceding studies, considering the different definition of QBO.”
23. Lines 271–272: 10 hPa is a difficult altitude level to use to discuss the dominance of the chemical process or dynamical (transport) process for ozone, because it is a transition altitude from dynamical control at lower altitudes (except for polar lower stratosphere) to chemical control to upper altitudes. For example, in panels (d) in Figs. 9 and 10 (DJF), the ozone and temperature anomalies have opposite signs in the SH mid and high latitudes, and this is considered to result from chemical control in the austral summer. In some regions of the NH high latitudes in DJF, the anomalies have the same sign, and this is considered to result from dynamical control in boreal winter (the negative anomalies indicate less heat and ozone transport from the midlatitudes).
24. Line 275, “anomalies at 10 hPa during QBOW phases”: These are anomalies from QBOE, that is, QBOW-QBOE.
25. Lines 277–279: Because Fig. 11 shows the Z difference between QBOW and QBOE, zonal asymmetry of Z in the QBOE should be mentioned.
26. Lines 287–288, “However, ozone anomalies are all positive over the Antarctic from the merged satellite data”: Which figure are you referring to? Fig. 8b? I think the data period is different between Fig. 8 and Fig. 11.
27. Lines 287–290: The authors should consider and discuss the difference in data periods (2002–2020 for Fig. 8 and 1979–2020 for Figs. 11 and S6).
28. Line 292, “during QBOW”: The distribution is an anomaly from QBOE.
29. Lines 303–304 and 305–306: The anomalies indicated by color are those from QBOE, not from the climatology.
30. Lines 321–328: I understand the necessity of showing the 3-D QBO anomaly in the Northern Hemisphere in DJF in Fig. 12, because in winter, planetary wave activity is active. Why did the authors explain the QBO anomalies in the NH and SH in SON? Is there nothing worth to mention in MAM? There is a description in lines 347–348 that seems to be the answer. Please mention it in Section 3.4.
31. Lines 332–335: Please mention the QBO phase.
32. Line 336, “a single-factor controlling simulation”: It would be better to say, “a sensitivity simulation.”
33. Line 340, 120W-30E: I found this longitude range in Conclusions and in the Abstract (line 12) but could not find it in the other sections. Is it inconsistent?
34. Lines 469–470: Should be “WMO (World Meteorological Organization), Scientific Assessment of Ozone Depletion: 2018, Global Ozone Research and Monitoring Project–Report No. 58, 588 pp., Geneva, Switzerland, 2018.”
35. Figs. 9–11: Why is the format for these figures different form that for Figs. 2, 3, 7, and 8? |
