the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Apr 2025
The global O2 airglow field as seen by the MATS satellite: strong equatorial maximum and planetary wave influence
Abstract. The Mesospheric Airglow/Aerosol Tomography and Spectroscopy (MATS) satellite was launched in November 2022, carrying as its main instrument a limb-viewing telescope with six spectral channels designed to image atmospheric O2 airglow and noctilucent clouds. Although the main objective of the satellite mission is to observe structures in the airglow introduced by propagating smaller-scale waves, the airglow emissions are also subjected to large-scale dynamical disturbances, such as atmospheric tides and planetary waves. This work presents large-scale structures in the airglow field as observed by the MATS limb imager from February 2023 to April 2023. The ascending (north-going) node in the satellite orbit, corresponding to the local sunset, is dominated by a strong equator maximum in the dayglow. In contrast, the descending (south-going) node, corresponding to the local sunrise, indicates an accompanying equatorial minimum. These characteristics align with the expected behaviour of atmospheric tidal movements. Specifically, a downwelling of atomic oxygen is expected over the equator at local sunset, contributing to airglow chemistry and enhancing the emissions. Another distinct feature in the data is a westward propagating disturbance observed at high latitudes in the Northern Hemisphere, maximising in February, interpreted as the quasi-10-day planetary wave of zonal wavenumber 1.
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Status: open (until 29 May 2025)
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RC1: 'Comment on egusphere-2025-1470', Anonymous Referee #1, 28 Apr 2025
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This paper reports on the nature of large-scale structures observed in Feb-Apr 2023 O2 limb emissions from the MATS satellite, which is in a Sun-synchronous ascending/descending dusk/dawn (17:30/05:30) orbit. It is well-written, provides new insights into the interaction between dynamics and chemistry, and is a nice addition to the literature.
specific comments
The authors do an excellent job explaining the complexities of the measurements in terms of dependencies on ascending vs descending, dayglow vs. nightglow, solar zenith angle, and month, so that geographical dependencies in the emissions can be ascribed to the underlying atmospheric dynamics.
The authors make creative use of the CTMT vertical winds to explain the equatorial enhancements in the 17:30 LST emissions at the equator and some aspects of the latitude and longitude dependencies, although this approach is limited by the fact that the Feb-April 2023 dynamics probably differs to any unknown degree from the 7-year climatology represented by the CTMT.
The authors also credibly argue that the emissions at high latitudes are modulated by the quasi-10-day planetary wave.
The arguments put forth by the authors in the context of previously published work is at about the right level, and the references to the literature are sufficient.
In future work the authors may wish to consider looking for eastward-propagating 2d-4d period ultra-fast Kelvin wave signals in their 10S-10N VER emissions.
I recommend publication of this paper as is.
technical corrections
Figure 1 caption should explain the meaning of the grey shading and cross-hatching.
Citation: https://doi.org/10.5194/egusphere-2025-1470-RC1 -
RC2: 'Comment on egusphere-2025-1470', Anonymous Referee #2, 04 May 2025
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The paper shows a first geophysical interpretation of measurements by the MATS satellite. A new satellite instrument is a major effort and confidence to the data needs to be gained and spread to the community by checking that such geophysical interpretations make sense. Therefore the study merits publication, even though not every detail is understood. However, the presented graphics should be made more consistent and I would request that easier comparison is facilitated.
Main comment:
The figures need more consistency: Give the main latitude lines at the left of the maps (once for each column) and the main longitudes once per each row. Use the same color for the same things e.g. (Volume emission rates currently jumping between viridis and a second color scale). Figure 7: Use the same longitude axis as for the maps -180° to 180°. I think it would be good to plot the vertical winds in the same format here as well.Suggestions:
a) For F7 Maybe have a look at JAWARA as well. What longitude structures do they have in their vertical winds?
b) For F8 Does SABER cover these latitudes? Could you do a similar Hovmoeller plot?Specific comments
L30 sentence structure?
L35 compare to completely ignoring PWs and tides, yes. But really more improtant is that GW amplitudes are usually smaller than these of Rossby waves and tides, i.e. that you get wrong GW amplitudes by wrong attribution in the fit. By subtracting the global scale waves first, you can also determine GWs larger than the analysis volume
L55 required to separate airglow emission signal from Rayleigh scattered background ?
L69 species -> would mean for me rather different molecules not states of the same molecule
F2 is this photons? photon counts? All real units are in the denominator ;
... and every map to two weeks ...
L91 ... examines how ... In the context I was first assuming that you would do a model calculation to separate effects, Reformulate slightly to make evident that this are your measurements.
L97 Motivation was given above, just state: For this study 1-D ...L131 Superposing six ... perturbations are isolated ...
Why isolate? What did you do here?F7 Maps run from 180W to 180E -> Do the same here! You could include three panels for the tidal winds
L149 does the model provide sigma? If yes you could check whether this is inside natural variations of the previous period
L176 in general agreement - you certainly have not shown to be compliant in details
L182 do you really want to conclude your paper this way, by an unquantified speculation about shortcomings in your temperature retrievals. In general, I would change the motivation slightly to general performance.
Citation: https://doi.org/10.5194/egusphere-2025-1470-RC2
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