Comparative study between ground-based observations and NAVGEM-HA analysis data in the mesosphere and lower thermosphere region

Stober, Gunter; Baumgarten, Kathrin; McCormack, John P.; Brown, Peter; Czarnecki, Jerry

doi:https://doi.org/10.5194/acp-20-11979-2020

Articles | Volume 20, issue 20

https://doi.org/10.5194/acp-20-11979-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-20-11979-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 20

Research article

|

26 Oct 2020

Research article |

| 26 Oct 2020

Comparative study between ground-based observations and NAVGEM-HA analysis data in the mesosphere and lower thermosphere region

Gunter Stober, Kathrin Baumgarten, John P. McCormack, Peter Brown, and Jerry Czarnecki

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Final revised paper (published on 26 Oct 2020)
Preprint (discussion started on 19 Nov 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Comments on Stober-et-al_ACP', Anonymous Referee #1, 16 Dec 2019
- AC1: 'Reply to Reviewer 1', Gunter Stober, 27 Jan 2020
RC2: 'Referee Comment', Anonymous Referee #2, 23 Dec 2019
- AC2: 'Reply to Reviewer 2', Gunter Stober, 27 Jan 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Anna Wenzel on behalf of the Authors (29 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Feb 2020) by William Ward

RR by Anonymous Referee #1 (17 Feb 2020)

RR by Anonymous Referee #3 (18 Feb 2020)

Suggestions for revision or reasons for rejection

Review report of “Comparative study between ground-based observations and NAVGEM-HA analysis data in the MLT region” by G. Stober et al.

General comments:
The present manuscript compared the MLT winds obtained from meteor radar measurements at three mid-to-high latitude stations and those from NAVGEM-HA for the daily-mean, semidiurnal tides and their day-to-day variability during the SSW. It is shown that the NAVGEM-HA reproduces the observed winds reasonably well.

A major concern is that the novelty is not clear. Especially, the same type of comparison has been already made extensively by McCormack et al. (2017) including semidiurnal tides and their variability during SSW (the same cases) with the same datasets. Another major concern is that the manuscript is not well organized and sounds quite redundant for me. I sometimes get lost about what the authors are trying to suggest.

A small novelty of this study may be applying APF technique. And if so, I might recommend that the manuscript just focus on a subject of the day-to-day variability during SSW, although I do not find the relevant discussion (Sec. 5) written straightforward. For the discussion of Pekeris resonance, the authors resort on the results of Forbes and Zhang (2012); but it should be noted that the resonance period depends on the circulation pattern for each SSW and I would suspect that FZ2012 results cannot be applied so simply.

For the above reasons, I am afraid I feel this manuscript needs substantial revisions before the publication may be considered. Please see below for specific comments.

Major comments:
1. I could not find what is a new finding for this study. McCormack et al. (2017) already made a comparison for the MLT winds between meteor radar measurements and NAVGEM-HA. They discussed the seasonality and day-to-day variability (during SSW) of semidiurnal tides. The present manuscript seems to emphasize a priority of ASF technique, but I do NOT think this technique is necessary at least for the analysis of seasonality (the variation with a relatively long time scale). In this context, I would barely guess that the discussion in Sec. 5.4 seems scientifically interesting; if so I might recommend the manuscript just concentrate on this subject, substantially reducing the rest part.

2. Partly because of the issue #1, the manuscript is not well organized. Particularly I think Section 5 should only focus on scientific discussions about the results shown in Section 4. Sec. 5.1 should be briefly merged into Sec. 3 and Section 5.2 be into Sec. 2.3, because they are all related to the data quality and analysis methods. Section 5.3 can be entirely removed, because the description here is like an Introduction of tides and a brief summary of results, not providing any detailed scientific discussions.

3. (L8-12 on p.7, L 3 on p.20) For the analysis, the authors assume that the vertical wavelengths of tides are much larger than 25 km. This may be true for semidiurnal tide but is not true for diurnal tide. The wavelength of the gravest propagating mode for the diurnal migrating tide is 25-30 km (the higher modes have shorter wavelengths; e.g., Chapman and Lindzen, 1970) and Davis et al. (2013) (cited by this manuscript) actually reported that the observed wavelengths were sometimes 20-30 km. In this sense, I am wondering whether the vertical retrieval kernel of 16 km damps a part of tides (esp. diurnal tides)? Also, is the averaging kernel applied also to NAVGEM-HA data for comparison?

4. Section 5.4 might be potentially interesting, but the main conclusions are not clear for the present manuscript. For example, the authors first say that the semidiurnal amplitude is enhanced after SSW (L3 on p.14) and the observed phase is approaching that of Pekeris resonance (~M2?) (L21-22 on p.24), but later said (L1 on p.26) that there was no amplification of lunar tide; these descriptions seem contradicting and confusing. At the final paragraph (L2 on p.27) it is suddenly suggested that the day-to-day variability is attributed to zonal winds, but this seems just a speculation without any evidences. At the beginning of the discussion (L21 on p.23), the authors say “we want to disentangle these three aspects…”. I wonders what is the final conclusion in this context?

5. For the Pekeris resonance, how is the resonance period determined? The resonance period depends on the background zonal wind and temperature each time. Forbes and Zhang (2012) examined the case for the January 2009. The present study considers the cases in the years 2010 and 2013, and so Forbes & Zhang’s results cannot be simply applied.

Minor comments:
1. L34 on p.6: What do you mean by “considering also a potential semidiurnal and terdiurnal tide”?
2. L1 on p.7: What do you mean by “regularization”? Do you mean that semidiurnal tide is fitted to the residual time series after removing the daily-mean and diurnal tide?
3. L10 on p.7: For the “16 km vertical retrieval kernel”, does this averaging(?) kernel put the same weights for the 16 km range? What kind of waves (wavelengths) would be effectively filtered with this kernel? (please also see Major comment #3).
4. L8 on p.11: It is said “the latter point (minimum in Nov.?) is not visible above Tavistock…” but for me, November minimum is clear at Tavistock.
5. L10 on p.12 “due to the coarser temporal resolution of the global data”: How can you reach this conclusion?
6. L10-11 on p.26: How are these two peaks explained vortex splitting event and planetary wave activity? Please describe more details.
7. L21-24 on p.28: I feel that this is just a speculation.
8. Captions of Fig.3-12…: Please do not repeat the same sentences in captions.

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ED: Reconsider after major revisions (06 Apr 2020) by William Ward

AR by Svenja Lange on behalf of the Authors (15 Jun 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (07 Jul 2020) by William Ward

RR by Anonymous Referee #3 (19 Jul 2020)

Suggestions for revision or reasons for rejection

Major comment (Pages and Line numbers are based on the manuscript with track of changes):

1. Although the present manuscript is much easier to follow compared with the previous one, I still cannot get the point of the very long discussion in Section 5.3. The authors say at Line 11 of Page 26 that “We discuss these three aspects using….”. I assume that these three aspects include (1) changes in mean wind, (2) nonmigrating tides and (3) lunar tidal amplification. At this point, readers expect the following paragraphs to discuss each of them; but the actual discussion is not straightforward (not well organized) but winding. For instance, another factor (i.e., ozone change) suddenly appears; I cannot understand how the discussion of vertical wavelengths is relevant here. While reading the answers to my previous major comment #4, I got the impression that the authors try to exclude the possibility of (2) and (3), and thus to speculate that (1) may be important (Is it true?). Since the suggestion that (3) is not the case seems important, please consider again making the discussion of this Section as concise as possible, really focusing on the discussion of each of (1)-(3). Otherwise readers may get lost and have difficulty getting to the final conclusion.

Other comments

1. (L7-8, p24) “higher temperature in NAVGEM-HA may also explain the higher wind magnitudes” I could not understand the logic.

2. (L11, p25) “?” Something is missing.

3. (Eqs (3-6)) The amplitude change with time does not need to be considered?

4. (Fig. 14) How long data are used for drawing Fig.14 (only during 2012/2013 SSW?; please describe such information in caption).

5. (L4 p.31) “Instrumental effects” How can you conclude this? For me the secondary peak appears close to the M2 frequency.

6. (Appendix) Figures should be cited in the text?

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ED: Publish subject to minor revisions (review by editor) (10 Aug 2020) by William Ward

AR by Gunter Stober on behalf of the Authors (17 Aug 2020) Author's response Manuscript

ED: Publish subject to technical corrections (31 Aug 2020) by William Ward

AR by Gunter Stober on behalf of the Authors (07 Sep 2020) Author's response Manuscript

Short summary

This paper presents a first cross-comparison of meteor ground-based observations and a meteorological analysis (NAVGEM-HA) to compare a seasonal climatology of winds and temperatures at the mesosphere/lower thermosphere. The validation is insofar unique as we not only compare the mean state but also provide a detailed comparison of the short time variability of atmospheric tidal waves. Our analysis questions previous results claiming the importance of lunar tides.