Quasi 18 h wave activity in ground-based observed mesospheric H<sub>2</sub>O over Bern, Switzerland

Lainer, Martin; Hocke, Klemens; Rüfenacht, Rolf; Kämpfer, Niklaus

doi:https://doi.org/10.5194/acp-17-14905-2017

Articles | Volume 17, issue 24

https://doi.org/10.5194/acp-17-14905-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-17-14905-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 24

Research article

|

18 Dec 2017

Research article |

| 18 Dec 2017

Quasi 18 h wave activity in ground-based observed mesospheric H₂O over Bern, Switzerland

Martin Lainer, Klemens Hocke, Rolf Rüfenacht, and Niklaus Kämpfer

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Final revised paper (published on 18 Dec 2017)
Preprint (discussion started on 11 Jan 2017)

Interactive discussion

Status: closed

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

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RC1: 'Review of "Quasi 18-hour wave activity in ground-based observed mesospheric H2O over Bern, Switzerland"', Anonymous Referee #2, 05 Feb 2017
RC2: 'review of Lainer et al', Anonymous Referee #3, 04 May 2017
RC3: 'Referee Comment', Anonymous Referee #4, 22 May 2017
AC1: 'Authors responses to all referees', Martin Lainer, 04 Jul 2017

Peer-review completion

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

AR by Martin Lainer on behalf of the Authors (04 Jul 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Jul 2017) by Gabriele Stiller

RR by Anonymous Referee #4 (28 Jul 2017)

Suggestions for revision or reasons for rejection

The revised manuscript mainly deals with observations of ground based mesospheric water vapour using the MIAWARA experiment near Bern (46.88° N) during 12 winter months from Oct 2014 – March 2015 and from Oct 2015 –March 2016. The authors found in 7 of these 12 months dominating oscillations with periods between 15 and 21 h. To interpret these oscillations, they used for case studies zonal winds from the Doppler wind radiometer WIRA at the same location. The combination of these datasets itself is valuable and suitable for publication in ACP. Compared to the previous version, this paper is nearly a new one focussing on own ground based measurements. I recommend to publish the manuscript after minor revision considering the following comments:
Comments
1) Page 3 Line 17: please explain “the area of the averaging kernel (the so-called measurements response)” in more detail or with a suitable reference. The measurement response is here given in percent in contrast to the WIRA (see Page 4, line 10)
2) Fig. 3 does not show the monthly time series for Winter 2015/2016 because it is identical with Fig. 2. However, in the present form these figures makes no sense and could be deleted, even if these both figures describes the data where the 18 hour oscillations appeared, because the authors didn’t explain the observed variability and they didn’t make any use of these figures in the discussion later on.
3) Page 3 Sect. 2.2 line 33: it is recommended to a add here a remark to lidar wind measurements with a higher vertical and temporal resolution as presented in the cited paper by Baumgarten et al., GRL, (2015) or in the paper by F.-J. Lübken, G. Baumgarten, J. Hildebrand and F. J. Schmidlin, Simultaneous and co-located wind measurements in the middle atmosphere by lidar and rocket-borne techniques, Atmos. Meas. Tech., 9, 3911-3919, doi:10.5194/amt-9-3911-2016, 2016, even if the application of the LIDAR wind technique requires a cloud free sky.
4) Page 5 line 5 : 0.25 – 0.35
5) Page 5 Sect 4.2: line 34 please add here a reference to Fig. 9a, because this is an important result.
6) The new discussion in Sect 4.3 contains two parts which could be separated in two subsections.
7) Page 7 line 34 below the period of 16.44 h corresponding to the inertia frequency at the latitude of Bern
8) Page 9 line 13 delete maybe

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RR by Anonymous Referee #3 (03 Aug 2017)

Suggestions for revision or reasons for rejection

They have removed much of the questionable analyses and thus the paper is more carefully presented. It is less interesting as a result although I guess the 18 hour periodicity observation could merit a short note in ACP. I have one more very significant concern- namely their wind result, and specifically Figure 9b, is simply not credible. Consider that they have only 4 days of useable data with a 6 hour integration time. That means they have 16 points. And with 16 points, they are claiming to resolve about 5 oscillations of the 18 hour wave? This is very hard to believe even for a stationary amplitude. But to show time dependence like in Figure 9b? The uncertainties in the spectral domain have to be enormous. The slightest bit of non-stationarity, for example, will, I believe, completely invalidate their results. Further, a detailed look at Figure 9 shows it to not be consistent with Figure 4. Thus above 0.2 hpa, Figure 4 shows a white area meaning no data on Dec 5. So at the highest altitudes, they have less than 16 points. One suggestion is to limit themselves to the pressure domain from 0.5 to 1.0 hpa where they have 7 days of data.

Other than the above, I have a few other minor comments plus some technical/grammar corrections.

1. On line 2, page 4, they state that they retrieved zonal and meridional winds, but show only the zonal component. What about the meridional component?
2. They mention meridional gradients in the H2O as possibly resulting from the edge of the polar vortex (line 10, page 8). I would argue that vertical gradients are equally if not more deserving of mention. They would not be expected to see oscillations in the H2O for pressures higher than about 0.2 hpa because the vertical gradient in the H2O becomes so weak. This means that the altitude variation of the 18 hour wave in H2O and in particular, a comparison with the wind results in Figure 9, is misleading. But then again, Figure 9b has bigger problems as per my top comment.
3. What are the vertical hash lines in Figures 2 and 3?
4. Grammar: line 18, page 3: say “A typical range for the threshold for the ….”
5. Grammar: line 22, page 3: “significantly”
6. Page 6, line 26: delete “water vapor”, saying “climatology as a priori information” is clear without redundancy
7. Page 6, line 28, whats Ac?
8. Figure 11 in general- I am very confused. If the a priori is seasonally varying, and only seasonally varying, why do they get any kind of short term oscillations as shown in the Figure? Why not use monthly averaged a priori, then the question of short term (quasi 2 day) oscillations becomes moot.
9. Continued of the above- line 31, page 6. This is unsubstantiated.

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RR by Anonymous Referee #2 (09 Aug 2017)

ED: Reconsider after major revisions (21 Aug 2017) by Gabriele Stiller

AR by Martin Lainer on behalf of the Authors (25 Sep 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Oct 2017) by Gabriele Stiller

RR by Anonymous Referee #3 (24 Oct 2017)

ED: Publish subject to minor revisions (review by editor) (01 Nov 2017) by Gabriele Stiller

Dear authors,

one of the referees provided a review on the revised version of your manuscript. He points out that he is satisfied with your response and the related changes to your manuscript. He has provided two minor comments and several editorial issues. Therefore I am happy to accept your manuscript provided you account for these comments in your final version.

In particular, he says:
**Reviewer comment**:
The substitution of an older wind dataset in Figs 4 and 9 is the appropriate thing to do and at least allows them to offer additional evidence for the 18 hour wave. The paper is suitable for publication subject to the two minor comments below plus two editorial/grammar comments.

First, the paragraph beginning on page 8, line 31 was a bit confusing and scattered. It starts out with a mention of the polar vortex and then includes comments about vertical gradients in H2O, a topic which does not seem to have much to do with the polar vortex. What are they trying to say with this paragraph? Is it that a direct comparison with wind data is complicated? OK, if so, then say so more directly and then follow the general statement with specific reasons why.

They could also helpfully add, someplace in the text- perhaps here or in the Conclusion, a simple comment that at very least the wind observations do provide an additional constraint for 3D models which might be trying to reproduce their data. If this wave has not yet been simulated or discussed in models such as WACCM or ECHAM, that would be useful information to know.
**End reviewer comment**

Please try to sharpen your argumentation in the paragraph beginning on page 8, line 31. If the reviewer's assumption is right, then please follow his suggestion. Maybe you could start the paragraph with the words: "Another complication in the comparison between wind and H2O wave signatures comes from oscillations in H2O that may be caused by the polar vortex edge moving across the observation site ...." or something similar.
The second comment of the reviewer is certainly helpful, and the conclusion section seems to be the right place for some words on this issue.

Please consider also the Editorial comments:
**Reviewer comment**
"Editorial:

Page 6, line 11. They should take care to emphasize that this is a qualitative observation only. Then, with also correcting the English: “Qualitatively, this looks like the same behavior as revealed by the water vapor analysis”

Page 9, line 28: “straightened out” is too informal for the academic literature. Suggest: “clarified”
**End reviewer comment**

Please submit your manuscript with the improvements discussed above.
Kind regards,
Gabriele Stiller

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AR by Martin Lainer on behalf of the Authors (09 Nov 2017) Author's response Manuscript

ED: Publish as is (13 Nov 2017) by Gabriele Stiller

AR by Martin Lainer on behalf of the Authors (14 Nov 2017)

Short summary

We report on middle-atmospheric water vapor measurements above Bern from the ground-based microwave radiometer MIAWARA (NDACC affiliated) during two winter periods of 6 months. Quasi 18 h oscillations of mesospheric water vapor above 0.1 hPa are observed. Further, the 18 h wave is seen in a zonal wind data set from the Doppler wind radiometer WIRA. Inertia-gravity-wave-induced fluctuations or a nonlinear coupling between tides and quasi 2-day waves are considered as possible drivers.

Quasi 18 h wave activity in ground-based observed mesospheric H2O over Bern, Switzerland

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Quasi 18 h wave activity in ground-based observed mesospheric H₂O over Bern, Switzerland