Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

Wüst, Sabine; Offenwanger, Thomas; Schmidt, Carsten; Bittner, Michael; Jacobi, Christoph; Stober, Gunter; Yee, Jeng-Hwa; Mlynczak, Martin G.; Russell III, James M.

doi:https://doi.org/10.5194/amt-11-2937-2018

Articles | Volume 11, issue 5

https://doi.org/10.5194/amt-11-2937-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-11-2937-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 11, issue 5

Research article

|

18 May 2018

Research article |

| 18 May 2018

Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

Sabine Wüst, Thomas Offenwanger, Carsten Schmidt, Michael Bittner, Christoph Jacobi, Gunter Stober, Jeng-Hwa Yee, Martin G. Mlynczak, and James M. Russell III

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Final revised paper (published on 18 May 2018)
Preprint (discussion started on 10 Oct 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Wust et al., 2017 review', Anonymous Referee #1, 03 Nov 2017
- AC1: 'Answer to referee 1', Sabine Wüst, 19 Dec 2017
RC2: 'Review', Anonymous Referee #2, 07 Nov 2017
- AC2: 'Answer to referee 2', Sabine Wüst, 19 Dec 2017
RC3: 'Review of Wüst et al', Anonymous Referee #3, 09 Nov 2017
- AC3: 'Answer to referee 3', Sabine Wüst, 19 Dec 2017

Peer-review completion

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

AR by Sabine Wüst on behalf of the Authors (19 Dec 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Jan 2018) by William Ward

RR by Anonymous Referee #3 (11 Jan 2018)

RR by Anonymous Referee #1 (15 Jan 2018)

RR by Alan Liu (15 Jan 2018)

Suggestions for revision or reasons for rejection

Review

This revised manuscript is improved from the first version. However, I still have some major concerns, with both how the results are presented, and how the analysis was done. In the following, I provided comments following the sequence of the manuscript, with major ones marked by '*'. I also commented to the authors' replies to my first review at the end.

* P2, L5-10: I understand that the authors try to state the different strengths of different instruments, but they are not described accurately. There needs to be a distinction between what parameters an instrument can directly measure or sensitive to, and what parameters can be derived or 'investigated' from the measurements. For example, lidars can measure vertical profiles so can directly measure vertical variations and provide vertical wavelength. But they can also be used to derive horizontal wavelength (e.g. as in Hu et al. 2002, Lu et al. 2009, Chen et al. 2013) for inertia-gravity waves. Airglow images can directly measure horizontal wavelength but can also be used to derive vertical wavelength when background horizontal wind. The main message here is that with enough known parameters, any instrument can be used to derive other missing gravity wave parameters. The distinctions among different instruments should be what they can directly measure, not what they can be used to derive.

* P2, L24-26: The real 'first time' here is only about deriving vertical wavelength. Mixing them with 'zonal, meridional' wavelengths is a bit misleading. As referenced by the authors, Wachter et al. (2015) have already shown the technique of deriving horizontal wavelength. Furthermore, as I pointed in the first review, the ability to derive vertical wavelength is partially contributable to the spatial information resolved by the scanning spectrometer (not new) and partially contributable to the horizontal wind from a nearby meteor radar (not this instrument). I suggest changing the title to 'Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning ...' Deriving intrinsic parameters (which the vertical wavelength depends on) using a single spectrometer is really the main contribution, not the horizontal wavelength.

P2, L5, 'sensitive for' -> 'sensitive to'
P2, L12, 'exclusively' -> 'only'. 'Exclusively' means no other instrument can do it.
P2, L30, Wave vector is always related to intrinsic wave frequency, not just for low- and medium-frequency waves.

P4, L11-12: missing the squares after 'km'
P4, L14-15: provide an estimated uncertainty of the 5 min averaged data

P5, L25-27: The sentence 'The radar delivers ...' describes only a very small part of the whole procedure of meteor radar wind retrieval. The main procedure is a fitting of all radial winds within a time-altitude bin in a least-square sense, assuming homogeneity within the bin. Since 'fit' and 'fitting technique' are mentioned in subsequent sentences, what the fit means need to be described first.

P6, L6: 'dynamical' -> 'dynamically'

* P8, L17-18: Even if the uncertainty of ground frequency is negligible, the intrinsic frequency may be not, because the latter depends on the wind in the direction of wave propagation. This Doppler wind depends on both the magnitude and direction of the background wind as well as the direction of the wave. In the analysis, the uncertainty in k and l are considered, but its indirect effect on the wave direction thus the component of the background wind in the direction of propagation is not. Please address this source of uncertainty.

P9, L2: It's not clear what 'too conservative' means. Does it mean the 10% is an underestimate or overestimate? Please clarify.

P10,
L5-6: Please clarify if this phase velocity is relative to the ground or intrinsic. Also, clarify in Figure 2b and its caption.
L21-22: I don't understand why the authors say 'no vertical ... profile is suitable' first and then 'more than one is available'. Please clarify.
L23: 'In one case' -> shouldn't it be 'In some cases'? There seem to be 31-19=12 cases that are without wind.
L24: 'referring to' -> 'on'

P7, L9-12: I think it's important to point out that this method looks for a single oscillation throughout an entire night (according to Wachter et al. 2015). If that's not the case, then the duration of each wave event should be given. Readers normally assume that a wave event could occur during part of a night but not the entire night, as I did at first.

P10, L25-26: If I understand correctly, the authors used one detected wave from the airglow and applied multiple nearby SABER profiles and corresponding winds to obtain multiple vertical wavelengths. This needs to be clarified in the text. It's also not clear whether all SABER data selected are within that time period. The spatial range is described in P5L3 but not the temporal range.

P11, L3: 'table 2' should 'Table 1'. It appears the authors have deleted Table 2.
P11, L4: evanescent waves are not necessarily damped.
P11, L21: Are there always 'Two wavelengths' in a SABER profile? Table 1 shows some SABER vertical wavelengths are over 15 km, which means there can only be one wavelength in the 60-80 km range.

* P11, L23-26: As the authors stated, SABER is sensitive only to oscillations with long horizontal wavelength. In Table 1, there are two cases (DOY 212 and 215) where the horizontal wavelength is only 200 km. It's true that SABER may be seeing at a horizontal angle not perpendicular to the wavefront, therefore the cancellation effect is not severe. This is however only a speculation but it can be easily demonstrated by additional analysis. Since both the wave direction and the direction of SABER sounding profile are known, their relative angles can be calculated to examine whether this speculation is correct. This needs to be done to verify if that's indeed the case.

P24: Table 1 caption should state that the period is 'ground-based.' as one reviewer asked. Adding a small subscript in the variable in the table header is not obvious to the readers.

P25: Table 1 should list the intrinsic wave periods. In the manuscript, as it is, there is no information at all about the background wind and its effect. For this reason, at least the intrinsic period (and/or wind in the direction of the wave, intrinsic frequency) is necessary. Another column needed is the percentage uncertainties of airglow vertical wavelength as shown in Figure 3b. The figure only shows the distributions but one cannot tell which uncertainty is for which wavelength.

Figure 1: Adding Figure 1 helps a lot. In the caption, the square after km is also missing. Since the area of the zenith square is given, it seems natural to also give the area of the off-zenith areas in the caption.

Comments to the authors' replies:

Regarding the tidal effect:
The effects of tide are not about affecting different FOV differently, but about changing the assumed 86 km altitude of OH airglow. This has two effects on the derive vertical wavelength. One is changing the assumed distance between different FOVs, therefore, the derived horizontal wavelength. This error depends on the horizontal wavelength (the shorter the larger the error). The other is changing the background wind needed to calculate the intrinsic frequency because the wind is averaged at airglow altitude. This error depends on the magnitude of the vertical wind shear. If the authors do not plan to address these issues in the analysis, they should at least be discussed.

About the SABER data:
The deficiency in using SABER data to derive vertical wavelength is real and I presented the reason. The authors' arguments such as, if that's the case, then 'I can never use data ...' or 'I can expand this ... to every instrument' are missing the point, and are not a scientific argument. My point is, deriving vertical wavelength from a snapshot of a vertical profile has its limitation, and authors should be aware of it. This is obvious in authors' own analysis process, in which different approaches give different results, and they have to pick what's most favorable. The main message here is that this comparison can neither validate, nor invalidate the vertical wavelength derived from OH data. Consequently, whether the derived OH vertical wavelength agrees or disagrees with the SABER data is really not meaningful, because both have uncertainties due to different reasons and the uncertainties are as large as their differences. Again, it is OK for making the comparison just for reference (since there is no other data to compare), but it is not a validation of the OH derived vertical wavelength.

References

Chen, C., X. Chu, A. J. McDonald, S. L. Vadas, Z. Yu, W. Fong, X. Lu (2013), Inertia-gravity waves in Antarctica: A case study using simultaneous lidar and radar measurements at McMurdo/Scott Base (77.8˚S, 166.7˚E), J. Geophys. Res. Atmos., 118, 2794-2808.

Hu, X., A. Z. Liu, C. S. Gardner, G. R. Swenson (2002), Characteristics of quasi-monochromatic gravity waves observed with lidar in the mesopause region at Starfire Optical Range, NM, Geophys. Res. Lett., 29, 2169.

Lu, X., A. Z. Liu, G. R. Swenson, T. Li, T. Leblanc, I. S. McDermid (2009), Gravity wave propagation and dissipation from the stratosphere to the lower thermosphere, J. Geophys. Res., 114, D11101.

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ED: Reconsider after major revisions (17 Jan 2018) by William Ward

AR by Sabine Wüst on behalf of the Authors (28 Feb 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Mar 2018) by William Ward

RR by Alan Liu (03 Apr 2018)

ED: Publish as is (07 Apr 2018) by William Ward

AR by Sabine Wüst on behalf of the Authors (16 Apr 2018)

Short summary

OH*-spectrometer measurements allow the analysis of gravity wave ground-based periods, but spatial information cannot necessarily be deduced. We combine the approach of Wachter at al. (2015) in order to derive horizontal wavelengths (but based on only one OH* spectrometer) with additional information about wind and temperature and compute vertical wavelengths. Knowledge of these parameters is a precondition for the calculation of further information such as the wave group velocity.