the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Sep 2024
Does total column ozone change during a solar eclipse?
Abstract. Several publications have reported that total column ozone (TCO) may oscillate with an amplitude of up to 10 Dobson Units during a solar eclipse while other researchers have not seen evidence that an eclipse leads to variations in TCO beyond the typical natural variability. Here, we try to resolve these contradictions by measuring short-term (seconds to minutes) variations in TCO using “global” (Sun and sky) and direct-Sun observations in the ultraviolet (UV) range with filter radiometers (GUVis-3511 and Microtops). Measurements were performed during three solar eclipses: the "Great American Eclipse" of 2024, which was observed in Mazatlán, Mexico, on 8 April 2024; a partial solar eclipse taking place in the United States on 14 October 2023 and observed at Fort Collins, Colorado (40.57° N, 105.10° W); and a total solar eclipse occurring in Antarctica on 4 December 2021 and observed at Union Glacier (79.76° S, 82.84° W). The upper limit of the amplitude of oscillations in TCO observed at Mazatlán, Fort Collins, and Antarctica were 0.7 %, 0.3 %, and 0.03 %, respectively. The variability at all sites was within that observed during times not affected by an eclipse. The larger variability at Mazatlán is likely due to cirrus clouds occurring throughout the day of the eclipse and the difficulty of separating changes in the ozone layer from cloud effects. These results support the conclusion that a solar eclipse does not lead to variations in TCO of more than ± 2 Dobson Units and likely much less, drawing into question reports of much larger oscillations. In addition to calculating TCO, we also present changes in the spectral irradiance and aerosol optical depth during eclipses and compare radiation levels observed during totality. The new results augment our understanding of the effect of a solar eclipse on the Earth's upper atmosphere.
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RC1: 'Comment on egusphere-2024-2659', Anonymous Referee #2, 18 Oct 2024
Review of the paper: “Does total column ozone change during a solar eclipse?” by Germar H. Bernhard et al.
General comments
This manuscript studies the short-term variability of the total ozone column (TCO) during solar eclipses in order to find out if the variations in this magnitude are real or, by contrary, the observed variability is derived from instrumental errors. For this goal, the authors work with TCO measurements recorded during three solar eclipses by GUVis-3511 and Microtops instruments. The topic is highly interesting and appropriated for ACP journal. In my opinion, the manuscript is clear and well written. Nevertheless, the following specific comments must be addressed by the authors before its final publication
Specific comments
- Section 4.1. TCO values are derived by GUVis-3511 from the wavelength pairs of 340/305 and 340/313 nm. The authors should justify this selection, for example, giving some references in which comparations of the TCO estimations by GUV instruments using different wavelength pairs against reference data were reported (e.g. Piedehierro et al., 2017). It must be noted that Dahlback (1996) proposed 320/305 pair, being taken as reference for later studies and adopted in the NILU-UV product software. Why this pair is not used for the present study?. For instance, the authors could obtain TCO values using 320/305 pair and these values be compared against SUV-100 spectroradiometer (subsection 5.1), following the comparison reported for TCO values derived from the wavelength pairs of 340/305 and 340/313 nm.
- Section 4.1 If the spectral response function of the GUV instruments used at Union Glacier were not characterized (lines 250-251), which are the uncertainties related to use the generic response functions on TCO estimations using equation 2?. This issue should be explained in detail.
- Sections 5.2.2, 5.3.2 and 5.4.2 In my opinion, these three sections about AOD behaviour during eclipses should be removed since are out of the scope of the manuscript. Additionally, the last paragraph of Section 6 should be accordingly rewritten, and Section 3.3 about Cimel instrument also removed. The authors can work in detail about this topic in the future, providing their results in a new manuscript focused on the measured of AOD during solar eclipses.
References
Dahlback, A., (1996) Measurements of biologically effective UV doses, total ozone abundances and cloud effects with multichannel, moderate bandwidth filter instruments, Appl. Opt. 35 (33), 6514-6521, doi: 10.1364/ao.35.006514.
Piedehierro, A.A., M.L. Cancillo, A. Serrano, M. Antón, and J.M. Vilaplana, (2017) Selection of suitable wavelengths for estimating total ozone column with multifilter UV radiometers, Atmos. Environ., 160, 124-131, doi: 10.1016/j.atmosenv.2017.04.022
Citation: https://doi.org/10.5194/egusphere-2024-2659-RC1 - AC2: 'Reply on RC1 by Anonymous Referee #2', Germar Bernhard, 15 Nov 2024
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RC2: 'Comment on egusphere-2024-2659', Anonymous Referee #1, 24 Oct 2024
The study by Bernhard et al discusses the variability in total ozone during three solar eclipses. The authors use an improved parameterization, relative to previous studies, for the Limp Darkening correction, which results in a more accurate total ozone retrieval (from direct sun ground based spectral measurements) during solar eclipses. They finally show that the variability in total ozone during such events is much smaller than what has been proposed in previous studies. The study contributes significantly to the understanding of processes that take place in the stratosphere during solar eclipses.
The paper is well written, well structured, and within the scope of the journal.
Minor comments and suggestions for technical corrections:
In addition to the studies that have been discussed and cited by the authors there are a few more recent studies that could be discussed in the introduction. For example:
https://www.mdpi.com/2072-4292/16/1/14
https://www.sciencedirect.com/science/article/pii/S1309104221001823
L342: Do the authors mean “critically dependent”?
L500: Should it be “functions” instead of “function”?
Citation: https://doi.org/10.5194/egusphere-2024-2659-RC2 - AC1: 'Reply on RC2 by Anonymous Referee #1', Germar Bernhard, 15 Nov 2024
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