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the Creative Commons Attribution 4.0 License.
| 17 Apr 2025
Extreme Concentric Gravity Waves Observed in the Mesosphere and Thermosphere Regions over Southern Brazil Associated with Fast-Moving Severe Thunderstorms
Abstract. Three groups of intense CGWs lasting over 10 hours were observed by an airglow imager at the Southern Space Observatory (SSO) in São Martinho da Serra (29.44° S, 53.82° W) in southern Brazil on 17–18 September 2023. These CGW events were simultaneously captured by spaceborne instruments, including the Atmospheric Infrared Sounder (AIRS) aboard Aqua, the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi NPP, and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument operating on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. The CGW caused significant airglow radiation perturbations exceeding 24 % and the distance of the wave center movement exceeded 400 km. These CGW events were caused by fast-moving deep convections observed by Geostationary Operational Environmental Satellite-16 (GOES-16). The weaker background wind field during the spring season transition provides the necessary conditions for CGWs to propagate from the lower atmosphere to the mesopause region. The 630 nm emission images were significantly contaminated by specific OH emission bands. The same CGW event was observed propagating from the OH airglow layer to the thermospheric OI 630.0 nm airglow layer. The asymmetric propagation of CGWs in the thermosphere may be due to the vertical wavelength changes caused by the Doppler-shifting effect of the background wind field. This multi-layer ground-based and satellite joint detection of CGWs offers an excellent perspective for examining the coupling of various atmospheric layers.
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RC1: 'Comment on egusphere-2025-1417', Anonymous Referee #1, 16 May 2025
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The paper "Extreme Concentric Gravity Waves Observed in the Mesosphere and Thermosphere Regions over Southern Brazil Associated with Fast-Moving Severe Thunderstorms" by Li et al. is a thorough and convincing study of gravity wave events observed by airglow imaging over Brazil. It is demonstrated that the gravity waves were likely excited by thunderstorms in the region. Fortunate propagation conditions allowed to observe full ring structures of the convective gravity waves in OH airglow images.
Overall, this study is very interesting and of relevance for the readership of ACP. The paper is well written, and the figures are of good quality. The paper is therefore recommended for publication in ACP after minor revisions.
For specific and technical comments see below.
SPECIFIC COMMENTS:
(1) l.41: You should add some more general references for convective gravity waves. For example, Fovell et al. (1992), or Piani et al. (2000):Fovell, R., Durran, D., and Holton, J. R.:
Numerical simulations of convectively generated stratospheric gravity waves,
J. Atmos. Sci., 49, 1427-1442, 1992.Piani, C., Durran, D., Alexander, M. J., and Holton, J. R.:
A Numerical Study of Three-Dimensional Gravity Waves Triggered by Deep Tropical Convection and Their Role in the Dynamics of the QBO,
J. Atmos. Sci., 57, 3689-3702, https://doi.org/10.1175/1520-0469(2000)057%3C3689:ansotd%3E2.0.co;2, 2000.(2) l.42: For the jet/front source mechanisms please add the reference Plougonven and Zhang (2014):
Plougonven, R., and Zhang, F.:
Internal gravity waves from atmospheric jets and fronts,
Rev. Geophys., 52, 33-76, doi:10.1002/2012RG000419, 2014.(3) l.58: You should mention that another method for determining the source location is backward ray tracing of gravity waves, which can also be performed for circular gravity wave patterns. An example is Ern et al. (2022):
Ern, M., Hoffmann, L., Rhode, S., and Preusse, P.:
The mesoscale gravity wave response to the 2022 Tonga volcanic eruption: AIRS and MLS satellite observations and source backtracing,
Geophysical Research Letters, 49, e2022GL098626, https://doi.org/10.1029/2022GL098626, 2022.
(4) l.121: Please provide a reference for the ABI-GOES instrument. For example:Schmit, T. J., Gunshor, M. M., Menzel, W. P., Gurka, J. J., Li, J., and Bachmeier, A. S.:
Introducing the next-generation advanced baseline imager on GOES-R,
Bull. Am. Met. Soc., 86, 1079-1096, doi:10.1175/BAMS-86-8-1079, 2005.(5) l.132, 133: The expression "image acquisition time" is somewhat misleading! AIRS is scanning repeatedly in the across-track direction taking footprints one-by-one. The AIRS data are then arranged into granules of 6min, each.
(6) Please provide references for the AIRS instrument! For example:
Aumann, H. H., et al.:
AIRS/AMSU/HSB on the Aqua mission: Design, science objective, data products, and processing systems,
IEEE Trans. Geosci. Remote Sens., 41, 253-264, 2003.Chahine, M. T., et al.:
AIRS: Improving weather forecasting and providing new data on greenhouse gases,
Bull. Am. Met. Soc., 87, 911-926, doi:10.1175/BAMS-87-7-911, 2006.(7) p.8: Please provide in Sect.2 also some information about the SABER instrument because also SABER data are used later in the manuscript.
(8) l.217: In Fig.4, upper row, there are also indications of 630nm wave structures that are superimposed on the OH signature that is highlighted by the yellow square. These wave fronts are perpendicular to the OH wave fronts. Similar findings in Fig.5. You should comment on this. Do you think these patterns are from a different wave?
(9) About Fig.4: The OH images and OI images were taken at almost the same time for demonstrating the contamination effect. Later in the manuscript you determine the time that the CGW takes to propagate from the OH altitude to the OI altitude to be around 1 hour. Therefore you should mention that some of the mismatches in the wave patterns shown in Fig.4 might be related to this.
(10) Fig.7: Suggest to replace the red text "large scale CGW" in the figure with just "large scale GW" because it is difficult to tell whether this would be part of a concentric GW pattern.
Even in the text you do not use the expression "CGW" for this wave pattern.(11) Caption of Fig.11: Please state whether these images are from OH, or from OI.
(12) l.342: Please check! The double-peak structure is seen mainly during the second overpass in the 07:18:23 UT profile, but not so much during the first overpass.
(13) l.368, 369: Please state that the flux is calculated for the altitude of the OH layer.
(14) l.374: How does this momentum flux compare to average values determined from SABER satellite data? A climatology is given, for example, in Ern et al. (2018).
Ern, M., Trinh, Q. T., Preusse, P., Gille, J. C., Mlynczak, M. G., Russell III, J. M., and Riese, M.:
GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings,
Earth Syst. Sci. Data, 10, 857-892, https://doi.org/10.5194/essd-10-857-2018, 2018.(15) l.387: The parameter alpha does not occur in Eq.(6), but only later in Eq.(7). Therefore the introduction of alpha should be moved there.
TECHNICAL COMMENTS:
l.18: CGWs -> concentric gravity waves (CGWs)
l.81: its role -> their role
l.250: Sumi -> Suomi
l.301-307: Same sentence appears twice. Delete one of them.
l.332: saber -> SABER
l.356: are expressed -> is expressed
l.358: is cancellation factor -> is a cancellation factor
l.417: can be -> and can be
l.475: for downloaded -> for download
l.479: delete "radiances data" (double occurence).
l.584: publication year of Heale et al. is 2022, not 2021.
Citation: https://doi.org/10.5194/egusphere-2025-1417-RC1 -
RC2: 'Comment on egusphere-2025-1417', Anonymous Referee #2, 22 May 2025
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Review of “Extreme Concentric Gravity Waves Observed in the Mesosphere and Thermosphere Regions over Southern Brazil Associated with Fast-Moving Severe Thunderstorms” by Q. Li et al.
General comments
The study presents detailed observations of intense concentric gravity waves (CGWs) in the mesosphere and thermosphere over southern Brazil during 17–18 September 2023, triggered by fast-moving severe thunderstorms. Utilizing dual-channel ground-based airglow imaging (OH and OI 630.0 nm) alongside multi-satellite data (GOES-16, AIRS, VIIRS, SABER), the authors documented three CGW events lasting over 10 hours, with amplitudes exceeding 24% and horizontal movements over 400 km. The findings highlight exceptional momentum flux and vertical energy transport from the troposphere to the mesosphere–lower thermosphere (MLT) region. The study also addresses contamination in 630.0 nm thermospheric imaging due to OH emissions and explains the observed asymmetric wave propagation via Doppler effects from background winds. This work advances understanding of atmospheric coupling and underscores the value of coordinated multi-layer observations.
The study is scientifically sound and presents a comprehensive and well-supported analysis of extreme concentric gravity waves using an impressive combination of ground-based and satellite observations. The paper is well written, generally concise, and includes clear figures that support the findings. However, in a few instances, the inclusion of additional details, particularly regarding data interpretation and methodological assumptions, could enhance clarity and aid reader comprehension. I recommend accepting the paper for publication, subject to minor revisions.
Specific comments
lines 33-34: Might be helpful to mention the typical height of the OH airglow layer (~87 km) and OI airglow layer (~250 km).
lines 40-46: While the discussion provides useful context on the sources of atmospheric gravity waves (AGWs), it would benefit from the inclusion of some earlier and potentially more foundational references. Citing key historical studies on different atmospheric gravity wave types and generation mechanisms would help establish a more comprehensive background for the reader.
lines 68-73: The authors should briefly explain what is meant by “dual-layer airglow observations” to provide clearer context for readers who may not be familiar with this technique. Specifically, clarifying that it involves simultaneous observations of airglow emissions from the mesosphere and thermosphere (e.g., OH and OI 630.0 nm layers) would help highlight the significance of this method for studying vertical wave propagation and atmospheric coupling.
lines 77-82: It would be helpful to clearly state where and when the observations were conducted to orient the reader. Additionally, the reported 24% amplitude is striking, providing context by specifying which previous studies or typical values this is being compared to would clarify its significance.
lines 104-116: The authors should clarify what is actually done in step #2 of the image processing chain. Specifically, more detail is needed on how the van Rhijn effect and atmospheric extinction are corrected, what parameters are used, and how the corrections are applied to the data. This would help readers better understand the methodology.
line 120: It seems the subsection introducing the SABER/TIMED measurements is missing?
lines 122-129: The authors are kindly requested to provide a reference for the ABI (Advanced Baseline Imager) instrument onboard GOES-16 to support the description of its capabilities.
Schmit, T. J., M. M. Gunshor, W. P. Menzel, J. J. Gurka, J. Li, and A. S. Bachmeier, 2005: INTRODUCING THE NEXT-GENERATION ADVANCED BASELINE IMAGER ON GOES-R. Bull. Amer. Meteor. Soc., 86, 1079–1096, https://doi.org/10.1175/BAMS-86-8-1079.
lines 133-135: The swath width of AIRS is approximately 1765 km, not 1600 km as stated (Hoffmann et al., 2014). I recommend citing Hoffmann et al. (2014) here, as their study offers important additional details on data processing methods—such as detrending—and discusses the sensitivity of AIRS stratospheric gravity wave observations, which are currently missing in this manuscript.
Hoffmann, L., Alexander, M. J., Clerbaux, C., Grimsdell, A. W., Meyer, C. I., Rößler, T., and Tournier, B.: Intercomparison of stratospheric gravity wave observations with AIRS and IASI, Atmos. Meas. Tech., 7, 4517–4537, https://doi.org/10.5194/amt-7-4517-2014, 2014.
lines 255-257: The relatively weak brightness temperature fluctuations observed by AIRS may result from the instrument’s limited sensitivity to short vertical wavelengths (see, e.g., Hoffmann et al., 2024). Consequently, the observed brightness temperature amplitudes are typically much lower than the actual stratospheric temperature fluctuations, especially for convective wave events with short vertical wavelengths.
line 260: In Figure 6, the convective gravity waves (CGWs) might become more visible if the colorbar range is adjusted, for example, by using a fixed, symmetric range of ±0.5 K. Additionally, the colorbar label should be corrected to read “Brightness temperature perturbation (K)” instead of “Temperature perturbation (k)” to avoid confusion between measured radiance (brightness temperature) and actual atmospheric temperature.
lines 376-378: The statement "These events represent the most intense vertical transport cases ever recorded" should be better contextualized. Please clarify the criteria or dataset scope that support this claim to avoid potential overgeneralization.
lines 388-393: Another relevant study for comparison is Yue et al. (2013), which also presents multi-layer observations of convective gravity waves and estimates propagation times from the troposphere to the airglow layer, similar to the approach in this study. Including a discussion of their findings could provide valuable context and strengthen the interpretation.
Yue, J., L. Hoffmann, and M. Joan Alexander (2013), Simultaneous observations of convective gravity waves from a ground-based airglow imager and the AIRS satellite experiment, J. Geophys. Res. Atmos., 118, 3178–3191, doi:10.1002/jgrd.50341.
lines 422-424: The authors should please clarify the actual detection threshold of the vertically integrated airglow observations, specifically the limit in terms of vertical wavelength.
Technical corrections
line 18: The acronym "CGW" (Concentric Gravity Wave) should be introduced in full when first mentioned.
line 28: change to “fast-moving deep convection” (singular)
lines 304-307: Remove redundant sentence “Figure 9c present…”
line 312: replace “ERA-5” by “ERA5”
line 332: replace “saber” by “SABER”
line 358: is _the_ cancellation factor
lines 386-387: from _the_ troposphere to _the_ airglow layer
Citation: https://doi.org/10.5194/egusphere-2025-1417-RC2
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