the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Feb 2026
Case Studies on Mesospheric Fronts at Low Latitudes over Brazil
Abstract. This study investigates four mesospheric front events observed over Cachoeira Paulista (23° S, 45° W), Brazil, between 2007 and 2008, using coordinated measurements from an all-sky airglow imager, meteor wind radar, and sodium temperature lidar. The events, recorded on 14–15 September 2007, 5 October 2007, 31 March 2008, and 3 September 2008, were classified as mesospheric bores, two undular and two turbulent based on airglow morphology and atmospheric background structure. Vertical profiles of wind and temperature, along with vertical wavenumber diagnostics, revealed the presence of thermal and thermal-Doppler ducts supporting the bores. Classical complementary emission responses were observed in single-duct environments, while multi-duct layering led to complex airglow signatures, including mixed bright and dark fronts. This is the first study in Brazil’s low-latitude region to employ simultaneous multi-instrument observations for mesospheric bore analysis, offering new insights into duct dynamics, emission behavior, and wave–duct interactions in the mesosphere and lower thermosphere.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Annales Geophysicae.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 03 Apr 2026)
- RC1: 'Comment on egusphere-2025-6569', Anonymous Referee #1, 10 Mar 2026 reply
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- 1
This paper describes four bore-like wave events observed in the mesosphere with an all-sky imager over South-East Brazil. A complete description of the atmospheric background conditions was also provided by coincident Na lidar and radar measurements. Bore-like events are trapped waves which are able to propagate over large distances. Their presence gives important information about the structure of the upper atmosphere.
The manuscript is clear and well-written. Although it provides some interesting results, these are not new. They just corroborate previous studies.
The paper gives a good overview of ducted waves science and a fairly complete description of the four investigated cases. However, the authors should answer the following comments/questions:
- A map illustrating the measurements would be useful, with the field of view of the imager and the locations of the Na lidar beams where they intersect the OH layer.
- How was Lh measured because the events all appeared as a single front?
- In equation (1), only some of the parts are used in this study, why is that? What about 1/4H2 and u'?
- Uncertainties are plotted on the figures, can you also provide the error calculations?
- Evidence for inversion layers is not always obvious, especially for events 2 and 4. It would be interesting to expand the background plots to the whole nights. Something similar to Figure 7 in Bossert et al., 2014 (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JD021460). It would also help providing an explanation for the origin of the ducting regions (large scale wave, tide?), and interpret the data, not just present it.
- Some figures could be nicer, especially 2, 5, 7, and 9, which look low quality.
Minor edits:
l. 83: I think SJC is west of Cachoeira Paulista!
SABER is mentioned in the data availability section but it's not clear when/how it was used in the study.