Articles | Volume 17, issue 2
Clim. Past, 17, 969–983, 2021

Special issue: Interdisciplinary studies of volcanic impacts on climate and...

Clim. Past, 17, 969–983, 2021

Research article 30 Apr 2021

Research article | 30 Apr 2021

On the phenomenon of the blue sun

Nellie Wullenweber et al.

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Cited articles

Ångström, A.: The Blue Sun of September 1950, Tellus, 3, 135–140,, 1951. a
Ball, J. G. C., Reed, B. E., Grainger, R. G., Peters, D. M., Mather, T. A., and Pyle, D. M.: Measurements of the complex refractive index of volcanic ash at 450, 546.7, and 650 nm, J. Geophys. Res.-Atmos., 120, 7747–7757,, 2015. a
Bates, D. R.: Rayleigh scattering by air, Planet. Space Sci., 32, 785–790,, 1984. a
Bauch, M.: The Day the Sun Turned Blue: A Volcanic Eruption in the Early 1460s and Its Possible Climatic Impact – A Natural Disaster Perceived Globally in the Late Middle Ages?, in: Historical Disaster Experiences. Transcultural Research – Heidelberg Studies on Asia and Europe in a Global Context, edited by: Schenk, G. J., Springer, Cham, 107–138, 2017. a
Bergstrom, R. W., Pilewskie, P., Russell, P. B., Redemann, J., Bond, T. C., Quinn, P. K., and Sierau, B.: Spectral absorption properties of atmospheric aerosols, Atmos. Chem. Phys., 7, 5937–5943,, 2007. a, b, c, d, e
Short summary
This study investigates the physical processes leading to the rare phenomenon of the sun appearing blue or green. The phenomenon is caused by anomalous scattering by, e.g., volcanic or forest fire aerosols. Unlike most other studies, our study includes a full treatment of the effect of Rayleigh scattering on the colour of the sun. We investigate different factors and revisit a historic example, i.e. the Canadian forest fires in 1950, that led to blue sun events in different European countries.