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Applied Optics

Applied Optics


  • Vol. 44, Iss. 27 — Sep. 20, 2005
  • pp: 5723–5736

Simulating colors of clear and partly cloudy skies

Stanley David Gedzelman  »View Author Affiliations

Applied Optics, Vol. 44, Issue 27, pp. 5723-5736 (2005)

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A model (SKYCOLOR) is developed that simulates the light and color of the sky and open cloud decks in the vertical plane including the Sun and the observer and animates the changes as the Sun goes down. Model skylight consists of sunbeams that are scattered toward the observer, but depleted by scattering and absorption in the Chappuis bands of ozone. SKYCOLOR includes the Earth’s curvature, atmospheric refraction, cloud shadows, and solar eclipses. Scattering is given a wavelength (λ) dependence of λ−4 for air molecules (Rayleigh scattering), λ−1 for tropospheric aerosols, and λ+1 for volcanic aerosol particles. Multiple scattering is calculated directly in clouds but is parameterized in clear air by decreasing the scattering rates of sunlight and of skylight in the Earth’s shadow by 30%.

© 2005 Optical Society of America

OCIS Codes
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(010.1310) Atmospheric and oceanic optics : Atmospheric scattering
(010.4030) Atmospheric and oceanic optics : Mirages and refraction
(010.4950) Atmospheric and oceanic optics : Ozone
(290.1090) Scattering : Aerosol and cloud effects
(290.1310) Scattering : Atmospheric scattering
(290.4210) Scattering : Multiple scattering
(330.1690) Vision, color, and visual optics : Color

Original Manuscript: January 7, 2005
Revised Manuscript: May 12, 2005
Manuscript Accepted: May 12, 2005
Published: September 20, 2005

Stanley David Gedzelman, "Simulating colors of clear and partly cloudy skies," Appl. Opt. 44, 5723-5736 (2005)

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  1. The Sky Color model is available from the author at sgedzelman@ccny.cuny.edu. Internet Sites for sky color simulations include http://www.vterrain.org/Atmosphere/ and http://ucsu.colorado.edu/~kuestern/Rtweb/startRT/html and http://www.ati.com/developer/SIGGRAPH03/PreethamSig2003CourseNotes.pdf and http://webexhibits.org/causesof-color/14B.html .
  2. A. Meinel, M. Meinel, Sunsets, Twilights and Evening Skies (Cambridge Univ., London, 1983).
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  4. P. Candy, Le Meraviglie del Cielo (II Castello, Milano, 1997).
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  6. S. D. Gedzelman, “Atmospheric optics in art,” Appl. Opt. 30, 3514–3522, 3550–3551 (1991). [CrossRef] [PubMed]
  7. W. J. Humphreys, Physics of the Air (Dover, New York, 1964, reprint of 1940 edition), pp. 557–570.
  8. M. Minnaert, The Nature of Light and Color in the Open Air (Dover, New York, 1954, reprint of 1938 edition), pp. 235–308.
  9. J. Tyndall, Philos. Mag. 37, 384 (1869).
  10. Rayleigh, J. W. Strutt, “On the light from the sky, its polarization and colour,” Philos. Mag. 41, 107–120274–279 (1871).
  11. G. V. Rozenberg, Twilight: A Study in Atmospheric Optics (Plenum, New York, 1966), pp. 10, 89.
  12. R. L. Lee, “Horizon brightness revisited: measurements and a model of clear-sky radiances,” Appl. Opt. 33, 4620–4628 (1994). [CrossRef] [PubMed]
  13. R. L. Lee, “Twilight and daytime colors of the clear sky,” Appl. Opt. 33, 4629–4638 (1994). [CrossRef] [PubMed]
  14. A. Meinel, M. Meinel, Sunsets, Twilights and Evening Skies (Cambridge University, London, 1983), p. 36.
  15. R. L. Lee, J. Hernández-Andrés, “Measuring and modeling twilight’s purple light,” Appl. Opt. 42, 445–457 (2003). [CrossRef] [PubMed]
  16. The model is available by e-mail at sgedzelman@ccny.cuny.edu.
  17. S. D. Gedzelman, J. Lock, “Simulating coronas in color,” Appl. Opt. 42, 497–504 (2003). [CrossRef] [PubMed]
  18. S. D. Gedzelman, “Simulating glories and cloudbows in color,” Appl. Opt. 42, 429–335 (2003). [CrossRef] [PubMed]
  19. S. D. Gedzelman, “Sky color near the horizon during a total solar eclipse,” Appl. Opt. 14, 2831–2837 (1975). [CrossRef] [PubMed]
  20. C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983).
  21. S. D. Gedzelman, “Simulating rainbows and halos in color,” Appl. Opt. 33, 4607–4614, 4958 (1994). [CrossRef] [PubMed]
  22. C. N. Adams, G. N. Plass, G. W. Kattawar, “The influence of ozone and aerosols on the brightness and color of the twilight sky,” J. Atmos. Sci. 31, 1662–1674 (1974). Raymond Lee pointed this out to me. [CrossRef]
  23. K.-N. Liou, An Introduction to Atmospheric Radiation, Vol. 26 of International Geophysics Series, (Academic, New York, 1980), p. 55.
  24. S. T. Henderson, Daylight and its Spectrum (Elsevier, New York, 1970), pp. 34–43.
  25. R. W. Bergstrom, P. B. Russell, P. Hignett, “Wavelength dependence of the absorption of black carbon particles: predictions and results from the TARFOX experiment and implications for the aerosol single scattering albedo,” J. Atmos. Sci. 59, 567–577 (2002). [CrossRef]
  26. C. F. Bohren, A. B. Fraser, “Colors of the sky,” Phys. Teacher 23, 267–272 (1985). [CrossRef]
  27. Ref. 3, pp. 33–45.
  28. D. L. Chandler, “The mystifying shuttle shadows,” Weatherwise 54(4), 14–15 (2001). [CrossRef]
  29. R. Greenler, “The NASA, Shuttle-launch dark-moon-ray mystery,” presented at the Topical Meeting in Meteorological Optics, Boulder, Colo., 6–8 June 2001.
  30. Many photographs of the sky near the horizon during total solar eclipses that show twilight colors are available at http://www.comet-track.com/eclipse . Courtesy of Bob Yen.

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