the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Nov 2025
GLOFI – A methodology and toolbox for scale-separation of satellite observations for analysis of gravity waves
Abstract. The direct analysis of atmospheric gravity waves (GWs) in temperature observations is difficult since the much stronger signal of large-scale temperature perturbations such as planetary waves obscure the perturbations due to GWs. The small-scale GW perturbations need to be isolated from the measurements by removing the large-scale temperature background, thereby revealing the object of analysis. In this study, the scale-separation via 2D spectral decomposition, which has the advantage of removing physical wave modes of zonal wavenumber up to 7 and wave frequency up to one cycle per day, is discussed. The technical implementation of this technique in a scale-separation Python-based toolbox, GLOFI (GLObal wave FIt), is detailed and demonstrated on a simulated satellite dataset for the ESA Earth Explorer 11 candidate CAIRT incorporating ECMWF ERA5 temperature data. Planetary wave spectra for the specified wavenumbers and frequencies are obtained by using a 28 day sliding window. These spectra are subsequently used to remove perturbations due to planetary waves from the measurements. This is followed by the removal of tides in a similar way but using a shorter 5-day sliding window and a fit of only stationary waves for ascending and descending orbits separately.
For the considered dataset, the variances of the difference between reference and GLOFI-generated temperature background are an order of magnitude smaller than GW temperature variances, which suggests that the method removes the large-scale waves to a degree that enables the separation of the GW perturbations. Furthermore, the obtained spectra can be used to generate a global temperature background grid which approximately resembles the actual global temperature field. More importantly, the temperature background estimated by GLOFI at the satellite track coordinates is almost identical to the actual reference temperatures along the tracks. Regarding the performance on data including GW perturbations, the isolated small-scale temperature perturbations are virtually identical to the actual reference GW perturbations from the model.
The GLOFI toolbox for scale separation of satellite observations is published as open access along this article.
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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
(13505 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
(13505 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-4602', Anonymous Referee #1, 20 Nov 2025
- AC2: 'Reply on RC1', Arun Jo Mathew, 23 Dec 2025
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RC2: 'Comment on egusphere-2025-4602', Anonymous Referee #2, 25 Nov 2025
This paper tackles an important issue: how to efficiently and accurately recover temperature fluctuations due to gravity waves that are masked by large scale planetary and tidal wave values in satellite data. It is particularly important to understand the strengths/limitations of new satellite instruments. The methodology/algorithm for using 2D spectral decomposition to remove the large-scale components due to planetary waves and tides is well described and tested using simulated data. The recovery of gravity wave fluctuations is convincing. However, like any technique there will be instrumental limitations that constraint the range of gravity wave scales that can be observed, as summarized in Appendix A for a range of techniques. It would help the reader to understand these limitations if there was a diagram similar to Fig 8 in Alexander et al QJRMS 136: 1103–1124 (2010) that describes observational constraints. More information is required on what GW scales can be recovered with these proposed new satellite measurements.
There are some minor issues:
- Appendix A is not mentioned in the body of the text. Probably should be referenced in about line 31.
- L 69: What does it mean that a tide is a ‘true resonant mode and propagating wave’?
- L230 ‘date’ not ‘data’
Citation: https://doi.org/10.5194/egusphere-2025-4602-RC2 - AC1: 'Reply on RC2', Arun Jo Mathew, 23 Dec 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-4602', Anonymous Referee #1, 20 Nov 2025
Review of “GLOFI - A methodology and toolbox for scale-separation of satellite
observations for analysis of gravity waves” by Mathew et al.
The manuscript describes an interesting methodology to derive GW perturbations by using a scale-separation Python-based toolbox. The methods and assumptions are mostly clearly outlined with some missing details. I recommend publication after addressing the following comments.
Specific comments:
- In Section 4.2 (Figure 4) and Appendix: In describing the comparisons between the temperature background estimated by GLOFI and actual temperature perturbations – “almost identical”, virtually identical” and the model spectrum is “very well” reproduced, “stronger deviations” is not quantitative. Please provide for e.g. differences and/or standard deviation etc.
- Section 2: (a) It might be useful to the reader to summarize the spatial technique in Strube et al (2020).
(b) The text and figures in Figure 2 are too small. Please make this more readable.
(c) Please clarify if ‘GW residuals’, ‘GW perturbations’, ‘residual GW perturbations’ (Sec 3) all mean the same thing
- There are 3 Appendices that are not referenced anywhere in the main text (except for the mention of Figure C1)
- Section 4.4/Figure 8. No discussion/summary of the differences is provided.
- Line 25: ‘… hard to resolve in atmospheric models” – please clarify that GWs can indeed be resolved in high-resolution models (e.g. Becket et al., 2022)
Becker, E., Vadas, S. L., Bossert, K., Harvey, V. L., Zülicke, C., & Hoffmann, L. (2022). A High-resolution whole-atmosphere model with resolved gravity waves and specified large-scale dynamics in the troposphere and stratosphere. Journal of Geophysical Research: Atmospheres, 127, e2021JD035018. https://doi.org/10.1029/2021JD035018
- Line 155: Please provide reference for the Savitzky-Golay (SG) filter
Typos etc.
- Provide abbreviations appropriately:
Line 67: what does DW1 stand for?
Line 88: what does PW stand for (Planetary Waves is mentioned several times previously)
- Line 84: “This gives….” – correct to, for e.g. This ‘manuscript/paper/study’ gives ….
- Line 204: Typo in 40°W
Citation: https://doi.org/10.5194/egusphere-2025-4602-RC1 - AC2: 'Reply on RC1', Arun Jo Mathew, 23 Dec 2025
-
RC2: 'Comment on egusphere-2025-4602', Anonymous Referee #2, 25 Nov 2025
This paper tackles an important issue: how to efficiently and accurately recover temperature fluctuations due to gravity waves that are masked by large scale planetary and tidal wave values in satellite data. It is particularly important to understand the strengths/limitations of new satellite instruments. The methodology/algorithm for using 2D spectral decomposition to remove the large-scale components due to planetary waves and tides is well described and tested using simulated data. The recovery of gravity wave fluctuations is convincing. However, like any technique there will be instrumental limitations that constraint the range of gravity wave scales that can be observed, as summarized in Appendix A for a range of techniques. It would help the reader to understand these limitations if there was a diagram similar to Fig 8 in Alexander et al QJRMS 136: 1103–1124 (2010) that describes observational constraints. More information is required on what GW scales can be recovered with these proposed new satellite measurements.
There are some minor issues:
- Appendix A is not mentioned in the body of the text. Probably should be referenced in about line 31.
- L 69: What does it mean that a tide is a ‘true resonant mode and propagating wave’?
- L230 ‘date’ not ‘data’
Citation: https://doi.org/10.5194/egusphere-2025-4602-RC2 - AC1: 'Reply on RC2', Arun Jo Mathew, 23 Dec 2025
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Manfred Ern
Maniyatt Pramitha
Peter Preusse
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(13505 KB) - Metadata XML
Review of “GLOFI - A methodology and toolbox for scale-separation of satellite
observations for analysis of gravity waves” by Mathew et al.
The manuscript describes an interesting methodology to derive GW perturbations by using a scale-separation Python-based toolbox. The methods and assumptions are mostly clearly outlined with some missing details. I recommend publication after addressing the following comments.
Specific comments:
(b) The text and figures in Figure 2 are too small. Please make this more readable.
(c) Please clarify if ‘GW residuals’, ‘GW perturbations’, ‘residual GW perturbations’ (Sec 3) all mean the same thing
Becker, E., Vadas, S. L., Bossert, K., Harvey, V. L., Zülicke, C., & Hoffmann, L. (2022). A High-resolution whole-atmosphere model with resolved gravity waves and specified large-scale dynamics in the troposphere and stratosphere. Journal of Geophysical Research: Atmospheres, 127, e2021JD035018. https://doi.org/10.1029/2021JD035018
Typos etc.
Line 67: what does DW1 stand for?
Line 88: what does PW stand for (Planetary Waves is mentioned several times previously)