the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Jul 2025
Spectral variability of gravity-wave kinetic and potential energy at 69°N: a seven-year lidar study
Abstract. We present the first multi-year study of gravity-wave (GW) kinetic Ekin and potential Epot energy spectra in the polar middle atmosphere based on simultaneous temperature and horizontal-wind measurements by the Doppler Rayleigh-lidar at the ALOMAR observatory (69°N, 16°E). The 7-year data set (2017–2023) comprising 100 soundings, each longer than 12 h, totalling >2700 h of observations with 150 m vertical and 5 min temporal resolution spanning 35–60 km. Overall, winter spectra exhibit significantly higher GW energies and variability than summer: the winter-to-summer amplitude ratio peaks at ≥10 at periods ≥12 h, declining to ∼1.5 above 3 h. This ratio is ∼2.5 in Epot across all vertical wavelengths, but peaks at ∼4 at 3 km in Ekin and approaches unity at smaller wavelengths. Winter Ekin exhibit a broad enhancement just above the inertial frequency f, whereas summer spectra show a sharp near-inertial peak and a distinct minimum at periods >11 h. Ekin/Epot shows strong dependence on observed frequency and vertical wavelength, exceeding values of 6 especially near f and short vertical wavelengths (<3 km), hinting at the non-separability of the GW spectrum. Frequency spectra showed -for the first time to be reported- broken power-laws at 35–40 km (more pronounced in summer), gradually merging into a simple power-law with a flatter slope as altitude increased. Our findings are critical for accurate spectral energy budget at high latitudes in the middle atmosphere and provide essential benchmarks to validate GW parameterisations in climate and numerical weather prediction models.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(6641 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-3267', Anonymous Referee #1, 08 Aug 2025
- AC1: 'Reply on RC1', Mohamed Mossad, 12 Sep 2025
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RC2: 'Comment on egusphere-2025-3267', Anonymous Referee #2, 17 Aug 2025
As with Reviewer 1, I find this paper well-written, clear and interesting. The dataset is an interesting one, the analysis is well-done, and the work is clearly presented with only extremely minor errors, nearly all of which are typographical.
I concur with all the points made by reviewer 1, and hence see no need to duplicate them again. I have the following additional typos, but I would be fine with the paper being accepted pretty much as-is, and definitely if the corrections suggested by Reviewer 1 were made:
L010 showed -> 10, but the sentence is a little tricky to read as a whole so couod be rephrased.
L013 budget -> budgets ("or an accurate...")
L020 - contribute significantly
L035 - a clearer definition of m* might be helpful here
L055: specific mention of exact instrument resolution jars - is this number special in some physical way, or just what your instrument measures?
L063 - don't think these references should be bracketed? Same for the rest of the paragraph
L065: they can also derive non-energy things! Suggest a slight rephrase :-)
L083: why is "midnight sun" capitalised?
L126: gain ->gaining, provide -> providing
L134: noctilucent (not capitalised)
L188: interleaved (again, not capitalised)
Intro to section 3 is a single extremely long paragraph - maybe chop in 2 or 3?
L289: expand out "approximately"
L492: "conforming" is being used here as a calque of the German term I think - in English it think you're after something like "consistent with previous work"?L496: "severely" -> "significantly"
L508: "significant" -> "significantly"
L584: "small" -> "smaller"
L683 "even when only the 1-3km band"
L728: I wouldn't capitalise the name of these theoriesCitation: https://doi.org/10.5194/egusphere-2025-3267-RC2 - AC2: 'Reply on RC2', Mohamed Mossad, 12 Sep 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-3267', Anonymous Referee #1, 08 Aug 2025
The work "Spectral variability of gravity-wave kinetic and potential energy at 69◦N: a seven-year lidar study" by Mossad and co-authors constitutes a comprehensive study of a unique dataset. The results are very relevant for this field of research and provide a reference for other studies and observations. The analysis is carefully done, and the presentation of results, the interpretation of measurements and the implications are well written. I have no major comments or questions, and recommend publication after minor corrections which are listed below.
Minor comments:
Abstract: In the abstract 2700 h of measurements and 100 soundings are mentioned, but the actual data used is less. Only summer and winter data are actually used in the study, e.g. from months Jan-Feb and Jun-Jul-Aug. They amount to 1091 h and 745 h according to Fig. 1 and Table 1. The actual number of used soundings is not given. I recommend to add these numbers to the abstract, and correct the number of soundings in line 742.
line 3: comprising --> comprises
line 65: add reference https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL104357
line 72: delete "will", delete "ever"
line 80: uniqueness of the ALOMAR location: also mention that it is situated at the coast and close to the Scandinavian mountain ridge
line 82: "only instrument in the world" change sentence to include https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JD026368 and https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017JD027386
line 97: "measuring horizontal wind velocities for 30 years" is that true? The Fiedler and Baumgarten (2024) reference only gives one example from 2017. Suggest to add "the capability for wind measurements was added in xx" or similar
line 90: Sec. 2.4 --> Sec. 4.4
line 105: two 1.8 m telescopes --> two tiltable 1.8 m telescopes
line 131: 27.5 h --> 27.6 h
line 143: It is not clear what a Reynolds decomposition is. Please explain.
line 145: delete "and turbulence". I don't think this can be seen at 5 min resolution.
line 147: Is there a difference between removing a 12-h running mean and a sounding-length running mean because the sounding length differs from sounding to sounding?
line 150: "the problem of long vertical stripes" I didn't find that in the reference. What kind of problem is that, an instrumental problem?
line 258: delete "fine"
line 259/260: 5 min resolution and 1221 individual spectra for winter adds to 102 h. Isn't winter supposed to comprise 745 h?
line 260: "is much smoother" Is that also because of the top-down integration?
line 283: what is "p" in the equation "b approx pd approx 1/6"?
Fig. 3: I suggest to add the dates in the legend to make clear that those are single cases and not winter and summer averages
line 332: upper stratosphere --> mid stratosphere?
line 345: measurements in (Hertzog.. --> measurements by Hertzog...
Table 2: For winter Epot energy a digit is missing for the uncertainty ("1"), in line 425 it is "1.4"
line 604: rabidly --> rapidly
line 676: "we need to first" --> "we first need to"
line 677: delete "do"
line 683: change "an artefact of" to "it is not a property of long-wavelength motions only, but.."?
line 707-713: this sentence is too long
check the use of brackets around citations: at least in l. 63, l. 64, l. 345, l. 350, l. 613, l. 662, l. 667 \citep should be changed to \citet
Citation: https://doi.org/10.5194/egusphere-2025-3267-RC1 - AC1: 'Reply on RC1', Mohamed Mossad, 12 Sep 2025
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RC2: 'Comment on egusphere-2025-3267', Anonymous Referee #2, 17 Aug 2025
As with Reviewer 1, I find this paper well-written, clear and interesting. The dataset is an interesting one, the analysis is well-done, and the work is clearly presented with only extremely minor errors, nearly all of which are typographical.
I concur with all the points made by reviewer 1, and hence see no need to duplicate them again. I have the following additional typos, but I would be fine with the paper being accepted pretty much as-is, and definitely if the corrections suggested by Reviewer 1 were made:
L010 showed -> 10, but the sentence is a little tricky to read as a whole so couod be rephrased.
L013 budget -> budgets ("or an accurate...")
L020 - contribute significantly
L035 - a clearer definition of m* might be helpful here
L055: specific mention of exact instrument resolution jars - is this number special in some physical way, or just what your instrument measures?
L063 - don't think these references should be bracketed? Same for the rest of the paragraph
L065: they can also derive non-energy things! Suggest a slight rephrase :-)
L083: why is "midnight sun" capitalised?
L126: gain ->gaining, provide -> providing
L134: noctilucent (not capitalised)
L188: interleaved (again, not capitalised)
Intro to section 3 is a single extremely long paragraph - maybe chop in 2 or 3?
L289: expand out "approximately"
L492: "conforming" is being used here as a calque of the German term I think - in English it think you're after something like "consistent with previous work"?L496: "severely" -> "significantly"
L508: "significant" -> "significantly"
L584: "small" -> "smaller"
L683 "even when only the 1-3km band"
L728: I wouldn't capitalise the name of these theoriesCitation: https://doi.org/10.5194/egusphere-2025-3267-RC2 - AC2: 'Reply on RC2', Mohamed Mossad, 12 Sep 2025
Peer review completion
Journal article(s) based on this preprint
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Irina Strelnikova
Robin Wing
Gerd Baumgarten
Michael Gerding
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(6641 KB) - Metadata XML
The work "Spectral variability of gravity-wave kinetic and potential energy at 69◦N: a seven-year lidar study" by Mossad and co-authors constitutes a comprehensive study of a unique dataset. The results are very relevant for this field of research and provide a reference for other studies and observations. The analysis is carefully done, and the presentation of results, the interpretation of measurements and the implications are well written. I have no major comments or questions, and recommend publication after minor corrections which are listed below.
Minor comments:
Abstract: In the abstract 2700 h of measurements and 100 soundings are mentioned, but the actual data used is less. Only summer and winter data are actually used in the study, e.g. from months Jan-Feb and Jun-Jul-Aug. They amount to 1091 h and 745 h according to Fig. 1 and Table 1. The actual number of used soundings is not given. I recommend to add these numbers to the abstract, and correct the number of soundings in line 742.
line 3: comprising --> comprises
line 65: add reference https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL104357
line 72: delete "will", delete "ever"
line 80: uniqueness of the ALOMAR location: also mention that it is situated at the coast and close to the Scandinavian mountain ridge
line 82: "only instrument in the world" change sentence to include https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JD026368 and https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017JD027386
line 97: "measuring horizontal wind velocities for 30 years" is that true? The Fiedler and Baumgarten (2024) reference only gives one example from 2017. Suggest to add "the capability for wind measurements was added in xx" or similar
line 90: Sec. 2.4 --> Sec. 4.4
line 105: two 1.8 m telescopes --> two tiltable 1.8 m telescopes
line 131: 27.5 h --> 27.6 h
line 143: It is not clear what a Reynolds decomposition is. Please explain.
line 145: delete "and turbulence". I don't think this can be seen at 5 min resolution.
line 147: Is there a difference between removing a 12-h running mean and a sounding-length running mean because the sounding length differs from sounding to sounding?
line 150: "the problem of long vertical stripes" I didn't find that in the reference. What kind of problem is that, an instrumental problem?
line 258: delete "fine"
line 259/260: 5 min resolution and 1221 individual spectra for winter adds to 102 h. Isn't winter supposed to comprise 745 h?
line 260: "is much smoother" Is that also because of the top-down integration?
line 283: what is "p" in the equation "b approx pd approx 1/6"?
Fig. 3: I suggest to add the dates in the legend to make clear that those are single cases and not winter and summer averages
line 332: upper stratosphere --> mid stratosphere?
line 345: measurements in (Hertzog.. --> measurements by Hertzog...
Table 2: For winter Epot energy a digit is missing for the uncertainty ("1"), in line 425 it is "1.4"
line 604: rabidly --> rapidly
line 676: "we need to first" --> "we first need to"
line 677: delete "do"
line 683: change "an artefact of" to "it is not a property of long-wavelength motions only, but.."?
line 707-713: this sentence is too long
check the use of brackets around citations: at least in l. 63, l. 64, l. 345, l. 350, l. 613, l. 662, l. 667 \citep should be changed to \citet