Preprints
https://doi.org/10.5194/egusphere-2024-2659
https://doi.org/10.5194/egusphere-2024-2659
30 Sep 2024
 | 30 Sep 2024

Does total column ozone change during a solar eclipse?

Germar H. Bernhard, George T. Janson, Scott Simpson, Raúl R. Cordero, Edgardo I. Sepúlveda Araya, Jose Jorquera, Juan A. Rayas, and Randall N. Lind

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.

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 preprint. The responsibility to include appropriate place names lies with the authors.
Germar H. Bernhard, George T. Janson, Scott Simpson, Raúl R. Cordero, Edgardo I. Sepúlveda Araya, Jose Jorquera, Juan A. Rayas, and Randall N. Lind

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2659', Anonymous Referee #2, 18 Oct 2024
    • AC2: 'Reply on RC1 by Anonymous Referee #2', Germar Bernhard, 15 Nov 2024
  • RC2: 'Comment on egusphere-2024-2659', Anonymous Referee #1, 24 Oct 2024
    • AC1: 'Reply on RC2 by Anonymous Referee #1', Germar Bernhard, 15 Nov 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2659', Anonymous Referee #2, 18 Oct 2024
    • AC2: 'Reply on RC1 by Anonymous Referee #2', Germar Bernhard, 15 Nov 2024
  • RC2: 'Comment on egusphere-2024-2659', Anonymous Referee #1, 24 Oct 2024
    • AC1: 'Reply on RC2 by Anonymous Referee #1', Germar Bernhard, 15 Nov 2024
Germar H. Bernhard, George T. Janson, Scott Simpson, Raúl R. Cordero, Edgardo I. Sepúlveda Araya, Jose Jorquera, Juan A. Rayas, and Randall N. Lind
Germar H. Bernhard, George T. Janson, Scott Simpson, Raúl R. Cordero, Edgardo I. Sepúlveda Araya, Jose Jorquera, Juan A. Rayas, and Randall N. Lind

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Short summary
Several publications have reported that total column ozone (TCO) may oscillate during solar eclipses while other researchers have not seen evidence of such fluctuations. Here, we try to resolve these contradictions by measuring variations in TCO during three solar eclipses. In all instances, the variability in TCO was within natural variability. We conclude that solar eclipses do not lead to measurable variations in TCO, drawing into question reports of much larger changes reported in the past.