Abstract

We have analyzed the colorimetric and spectral characteristics of 2600 daylight spectra (global spectral irradiances on a horizontal surface) measured for all sky states during a 2-year period at Granada, Spain. We describe in detail the chromaticity coordinates, correlated color temperatures (CCT), luminous efficacies, and relative UV and IR contents of Granada daylight. The chromaticity coordinates of Granada daylight lie far above the CIE locus at high CCTs (>9000 K), and a CCT of 5700 K best typifies this daylight. Our principal-components analysis shows that Granada daylight spectra can be adequately represented by using six-dimensional linear models in the visible, whereas seven-dimensional models are required if we include the UV or near-IR. Yet on average only three-dimensional models are needed to reconstruct spectra that are colorimetrically indistinguishable from the original spectra.

© 2001 Optical Society of America

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References

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  1. S. T. Henderson, D. Hodgkiss, “The spectral energy distribution of daylight,” Br. J. Appl. Phys. 14, 125–131 (1963).
    [CrossRef]
  2. D. B. Judd, D. L. MacAdam, G. Wyszecki, “Spectral distribution of typical daylight as a function of correlated colour temperature,” J. Opt. Soc. Am. 54, 1031–1041 (1964).
    [CrossRef]
  3. G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).
  4. H. R. Condit, F. Grum, “Spectral energy distribution of daylight,” J. Opt. Soc. Am. 54, 937–944 (1964).
    [CrossRef]
  5. Y. Nayatani, G. Wyszecki, “Color of daylight from north sky,” J. Opt. Soc. Am. 53, 626–629 (1963).
    [CrossRef]
  6. J. F. Collins, “The colour temperature of daylight,” Br. J. Appl. Phys. 16, 527–532 (1965).
    [CrossRef]
  7. G. T. Winch, M. C. Boshoff, C. J. Kok, A. G. du Toit, “Spectroradiometric and colorimetric characteristics of daylight in the southern hemisphere: Pretoria, South Africa,” J. Opt. Soc. Am. 56, 456–464 (1966).
    [CrossRef]
  8. S. R. Das, V. D. P. Sastri, “Spectral distribution and color of tropical daylight,” J. Opt. Soc. Am. 55, 319–323 (1965).
    [CrossRef]
  9. V. D. P. Sastri, S. R. Das, “Typical spectral distributions and colour for tropical daylight,” J. Opt. Soc. Am. 58, 391–398 (1968).
    [CrossRef]
  10. Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).
  11. A. W. S. Tarrant, “The spectral power distribution of daylight,” Trans. Illum. Eng. Soc. 33, 75–82 (1968).
  12. G. L. Knestrick, J. A. Curcio, “Measurements of the spectral radiance of the horizon sky,” (Naval Research Laboratory, Washington, D.C., 1967).
  13. V. D. P. Sastri, S. B. Manamohanan, “Spectral distribution and colour of north sky at Bombay,” J. Phys. D Appl. Phys. 4, 381–386 (1971).
    [CrossRef]
  14. E. R. Dixon, “Spectral distribution of Australian daylight,” J. Opt. Soc. Am. 68, 437–450 (1978).
    [CrossRef]
  15. G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982), pp. 144–146.
  16. D. Slater, G. Healey, “Analyzing the spectral dimensionality of outdoor visible and near-infrared illumination functions,” J. Opt. Soc. Am. A 15, 2913–2920 (1998).
    [CrossRef]
  17. J. Romero, A. Garcı́a-Beltrán, J. Hernández-Andrés, “Linear bases for representation of natural and artificial illuminants,” J. Opt. Soc. Am. A 14, 1007–1014 (1997).
    [CrossRef]
  18. R. L. Lee, “Twilight and daytime colors of the clear sky,” Appl. Opt. 33, 4629–4638, 4959 (1994).
    [CrossRef] [PubMed]
  19. See Ref. 15, p. 11.
  20. S. T. Henderson, Daylight and Its Spectrum (American Elsevier, New York, 1970).
  21. L. T. Maloney, B. A. Wandell, “Color constancy: a method for recovering surface spectral reflectance,” J. Opt. Soc. Am. A 3, 29–33 (1986).
    [CrossRef] [PubMed]
  22. D. H. Marimont, B. A. Wandell, “Linear models of surface and illuminant spectra,” J. Opt. Soc. Am. A 9, 1905–1913 (1992).
    [CrossRef] [PubMed]
  23. J. Hernández-Andrés, “Caracterı́sticas espectrales y colorimétricas de la luz-dı́a y luz-cielo en Granada,” Ph.D. dissertation (Universidad de Granada, Granada, Spain, 1999).
  24. J. Hernández-Andrés, J. Romero, A. Garcı́a-Beltrán, J. L. Nieves, “Testing linear models on spectral daylight measurements,” Appl. Opt. 37, 971–977 (1998).
    [CrossRef]
  25. J. Hernández-Andrés, R. L. Lee, J. Romero, “Calculating correlated color temperatures across the entire gamut of daylight and skylight chromaticities,” Appl. Opt. 38, 5703–5709 (1999).
    [CrossRef]
  26. LI-1800 spectroradiometer from LI-COR, Inc., 4421 Superior Street, Lincoln, Nebraska 68504-1327.
  27. C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
    [CrossRef]
  28. D. R. Myers, “Estimates of uncertainty for measured spectra in the SERI spectral solar radiation database,” Sol. Energy 43, 347–353 (1989).
    [CrossRef]
  29. S. Nann, C. Riordan, “Solar spectral irradiance under clear and cloudy skies: measurement and semiempirical model,” J. Appl. Meteorol. 30, 447–462 (1991).
    [CrossRef]
  30. See Ref. 15, pp. 306–310.
  31. See Ref. 15, pp. 224–225.
  32. See Ref. 15, pp. 256–259.
  33. R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
    [CrossRef]
  34. J. A. Olseth, A. Skartveit, “Observed and modelled hourly luminous efficacies under arbitrary cloudiness,” Sol. Energy 42, 221–233 (1989).
    [CrossRef]
  35. R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
    [CrossRef]
  36. B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).
  37. S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
    [CrossRef]
  38. J. P. S. Parkinnen, J. Hallikainen, T. Jaaskelainen, “Characteristic spectra of Munsell colors,” J. Opt. Soc. Am. A 6, 318–322 (1989).
    [CrossRef]
  39. ASTM Committee E-12, “Standard practice for computing the colors of objects by using the CIE system (E 308-95), in ASTM standards on color and appearance measurements,” (American Standards for Testing and Materials, Philadelphia, Pa., 1996), pp. 262–263.
  40. The white point for the transformation to L*u*v*space was the standard illuminant D65.

1999 (1)

1998 (2)

1997 (1)

1996 (1)

S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
[CrossRef]

1995 (1)

B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).

1994 (1)

R. L. Lee, “Twilight and daytime colors of the clear sky,” Appl. Opt. 33, 4629–4638, 4959 (1994).
[CrossRef] [PubMed]

1992 (1)

1991 (1)

S. Nann, C. Riordan, “Solar spectral irradiance under clear and cloudy skies: measurement and semiempirical model,” J. Appl. Meteorol. 30, 447–462 (1991).
[CrossRef]

1990 (1)

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

1989 (4)

J. A. Olseth, A. Skartveit, “Observed and modelled hourly luminous efficacies under arbitrary cloudiness,” Sol. Energy 42, 221–233 (1989).
[CrossRef]

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

D. R. Myers, “Estimates of uncertainty for measured spectra in the SERI spectral solar radiation database,” Sol. Energy 43, 347–353 (1989).
[CrossRef]

J. P. S. Parkinnen, J. Hallikainen, T. Jaaskelainen, “Characteristic spectra of Munsell colors,” J. Opt. Soc. Am. A 6, 318–322 (1989).
[CrossRef]

1987 (1)

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

1986 (1)

1978 (1)

1971 (1)

V. D. P. Sastri, S. B. Manamohanan, “Spectral distribution and colour of north sky at Bombay,” J. Phys. D Appl. Phys. 4, 381–386 (1971).
[CrossRef]

1968 (2)

A. W. S. Tarrant, “The spectral power distribution of daylight,” Trans. Illum. Eng. Soc. 33, 75–82 (1968).

V. D. P. Sastri, S. R. Das, “Typical spectral distributions and colour for tropical daylight,” J. Opt. Soc. Am. 58, 391–398 (1968).
[CrossRef]

1967 (1)

Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).

1966 (1)

1965 (2)

S. R. Das, V. D. P. Sastri, “Spectral distribution and color of tropical daylight,” J. Opt. Soc. Am. 55, 319–323 (1965).
[CrossRef]

J. F. Collins, “The colour temperature of daylight,” Br. J. Appl. Phys. 16, 527–532 (1965).
[CrossRef]

1964 (2)

1963 (3)

Y. Nayatani, G. Wyszecki, “Color of daylight from north sky,” J. Opt. Soc. Am. 53, 626–629 (1963).
[CrossRef]

S. T. Henderson, D. Hodgkiss, “The spectral energy distribution of daylight,” Br. J. Appl. Phys. 14, 125–131 (1963).
[CrossRef]

G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).

Barron, J.

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

Belbin, A. A.

G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).

Bittar, A.

S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
[CrossRef]

Boshoff, M. C.

Chamberlin, G. J.

G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).

Collins, J. F.

J. F. Collins, “The colour temperature of daylight,” Br. J. Appl. Phys. 16, 527–532 (1965).
[CrossRef]

Condit, H. R.

Curcio, J. A.

G. L. Knestrick, J. A. Curcio, “Measurements of the spectral radiance of the horizon sky,” (Naval Research Laboratory, Washington, D.C., 1967).

Das, S. R.

Delaunay, J. J.

B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).

Dixon, E. R.

du Toit, A. G.

Garci´a-Beltrán, A.

Grum, F.

Hallikainen, J.

Healey, G.

Henderson, S. T.

S. T. Henderson, D. Hodgkiss, “The spectral energy distribution of daylight,” Br. J. Appl. Phys. 14, 125–131 (1963).
[CrossRef]

S. T. Henderson, Daylight and Its Spectrum (American Elsevier, New York, 1970).

Hernández-Andrés, J.

Hitani, M.

Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).

Hodgkiss, D.

S. T. Henderson, D. Hodgkiss, “The spectral energy distribution of daylight,” Br. J. Appl. Phys. 14, 125–131 (1963).
[CrossRef]

Hulstrom, R.

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Ineichen, P.

B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

Jaaskelainen, T.

Jennings, C.

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Judd, D. B.

Knestrick, G. L.

G. L. Knestrick, J. A. Curcio, “Measurements of the spectral radiance of the horizon sky,” (Naval Research Laboratory, Washington, D.C., 1967).

Kok, C. J.

Lawrence, A.

G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).

Lee, R. L.

MacAdam, D. L.

Maloney, L. T.

Manamohanan, S. B.

V. D. P. Sastri, S. B. Manamohanan, “Spectral distribution and colour of north sky at Bombay,” J. Phys. D Appl. Phys. 4, 381–386 (1971).
[CrossRef]

Marimont, D. H.

Marion, W.

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Michalsky, J.

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

Minato, H.

Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).

Molineaux, B.

B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).

Myers, D. R.

D. R. Myers, “Estimates of uncertainty for measured spectra in the SERI spectral solar radiation database,” Sol. Energy 43, 347–353 (1989).
[CrossRef]

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Nann, S.

S. Nann, C. Riordan, “Solar spectral irradiance under clear and cloudy skies: measurement and semiempirical model,” J. Appl. Meteorol. 30, 447–462 (1991).
[CrossRef]

Nayatani, Y.

Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).

Y. Nayatani, G. Wyszecki, “Color of daylight from north sky,” J. Opt. Soc. Am. 53, 626–629 (1963).
[CrossRef]

Nieves, J. L.

Olseth, J. A.

J. A. Olseth, A. Skartveit, “Observed and modelled hourly luminous efficacies under arbitrary cloudiness,” Sol. Energy 42, 221–233 (1989).
[CrossRef]

Parkinnen, J. P. S.

Perez, R.

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

Pohlen, S.

S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
[CrossRef]

Riordan, C.

S. Nann, C. Riordan, “Solar spectral irradiance under clear and cloudy skies: measurement and semiempirical model,” J. Appl. Meteorol. 30, 447–462 (1991).
[CrossRef]

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Romero, J.

Ruck, B.

S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
[CrossRef]

Sastri, V. D. P.

Seals, R.

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

Skartveit, A.

J. A. Olseth, A. Skartveit, “Observed and modelled hourly luminous efficacies under arbitrary cloudiness,” Sol. Energy 42, 221–233 (1989).
[CrossRef]

Slater, D.

Stewart, R.

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

Stiles, W. S.

G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982), pp. 144–146.

Tarrant, A. W. S.

A. W. S. Tarrant, “The spectral power distribution of daylight,” Trans. Illum. Eng. Soc. 33, 75–82 (1968).

Wandell, B. A.

Webster, K.

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

Whitaker, C.

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

Winch, G. T.

Wyszecki, G.

Appl. Opt. (3)

Br. J. Appl. Phys. (2)

J. F. Collins, “The colour temperature of daylight,” Br. J. Appl. Phys. 16, 527–532 (1965).
[CrossRef]

S. T. Henderson, D. Hodgkiss, “The spectral energy distribution of daylight,” Br. J. Appl. Phys. 14, 125–131 (1963).
[CrossRef]

Bull Electrotech. Lab. (1)

Y. Nayatani, M. Hitani, H. Minato, “Chromaticity and spectral energy distribution of daylight from north sky at Amagasaki, Japan,” Bull Electrotech. Lab. 31, 1127–1135 (1967).

J. Appl. Meteorol. (1)

S. Nann, C. Riordan, “Solar spectral irradiance under clear and cloudy skies: measurement and semiempirical model,” J. Appl. Meteorol. 30, 447–462 (1991).
[CrossRef]

J. Opt. Soc. Am. (7)

J. Opt. Soc. Am. A (5)

J. Phys. D Appl. Phys. (1)

V. D. P. Sastri, S. B. Manamohanan, “Spectral distribution and colour of north sky at Bombay,” J. Phys. D Appl. Phys. 4, 381–386 (1971).
[CrossRef]

Light Light. (1)

G. J. Chamberlin, A. Lawrence, A. A. Belbin, “Observations on the related colour temperature of north daylight in southern England,” Light Light. 56, 70–72 (1963).

Sol. Energy (7)

C. Riordan, D. R. Myers, R. Hulstrom, W. Marion, C. Jennings, C. Whitaker, “Spectral solar radiation data base at SERI,” Sol. Energy 20, 67–79 (1989).
[CrossRef]

D. R. Myers, “Estimates of uncertainty for measured spectra in the SERI spectral solar radiation database,” Sol. Energy 43, 347–353 (1989).
[CrossRef]

R. Perez, K. Webster, R. Seals, R. Stewart, J. Barron, “Variations of the luminous efficacy of global and diffuse radiation and zenith luminance with weather conditions—description of a potential method to generate key daylight availability data from existing solar radiation data bases,” Sol. Energy 38, 33–44 (1987).
[CrossRef]

J. A. Olseth, A. Skartveit, “Observed and modelled hourly luminous efficacies under arbitrary cloudiness,” Sol. Energy 42, 221–233 (1989).
[CrossRef]

R. Perez, P. Ineichen, R. Seals, J. Michalsky, R. Stewart, “Modeling daylight availability and irradiance components from direct and global irradiance,” Sol. Energy 44, 271–289 (1990).
[CrossRef]

B. Molineaux, P. Ineichen, J. J. Delaunay, “Direct luminous efficacy and atmospheric turbidity—improving model performance,” Sol. Energy 55, 125–137 (1995).

S. Pohlen, B. Ruck, A. Bittar, “Evaluation of the Perez luminous efficacy models for a southern hemisphere site (New Zealand -41°S, 175°E),” Sol. Energy 57, 307–315 (1996).
[CrossRef]

Trans. Illum. Eng. Soc. (1)

A. W. S. Tarrant, “The spectral power distribution of daylight,” Trans. Illum. Eng. Soc. 33, 75–82 (1968).

Other (11)

G. L. Knestrick, J. A. Curcio, “Measurements of the spectral radiance of the horizon sky,” (Naval Research Laboratory, Washington, D.C., 1967).

See Ref. 15, p. 11.

S. T. Henderson, Daylight and Its Spectrum (American Elsevier, New York, 1970).

LI-1800 spectroradiometer from LI-COR, Inc., 4421 Superior Street, Lincoln, Nebraska 68504-1327.

See Ref. 15, pp. 306–310.

See Ref. 15, pp. 224–225.

See Ref. 15, pp. 256–259.

G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae (Wiley, New York, 1982), pp. 144–146.

J. Hernández-Andrés, “Caracterı́sticas espectrales y colorimétricas de la luz-dı́a y luz-cielo en Granada,” Ph.D. dissertation (Universidad de Granada, Granada, Spain, 1999).

ASTM Committee E-12, “Standard practice for computing the colors of objects by using the CIE system (E 308-95), in ASTM standards on color and appearance measurements,” (American Standards for Testing and Materials, Philadelphia, Pa., 1996), pp. 262–263.

The white point for the transformation to L*u*v*space was the standard illuminant D65.

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Figures (12)

Fig. 1
Fig. 1

Relative spectral irradiance, normalized at 560 nm, for three different daylight SPDs measured in Granada.

Fig. 2
Fig. 2

CIE 1931 chromaticities of our 2600 Granada daylight measurements (circles) overlaid on the CIE daylight locus (dashed curve), the Planckian locus (solid curve with squares), and the Granada daylight locus (dotted curve). The inset shows the entire CIE 1931 diagram and Planckian locus.

Fig. 3
Fig. 3

Histogram of inverse correlated color temperature (CCT) for our 2600 Granada daylight spectra. Each bin is 5 MK-1 wide.

Fig. 4
Fig. 4

Histogram of inverse CCT (in MK-1) for Granada daylight measured under clear and overcast skies.

Fig. 5
Fig. 5

CCT versus solar elevation h0 at 5° intervals for clear and overcast skies. Squares and circles indicate mean CCTs; each error bar spans 2 standard deviations.

Fig. 6
Fig. 6

Photopic luminous efficacies [based on 3001100 nm E(λ) integrals] as a function of h0 for our 2600 Granada daylight spectra.

Fig. 7
Fig. 7

Ratios of ultraviolet (300–380 nm) to visible (380–780 nm) irradiance as a function of inverse CCT (in MK-1). The solid curve shows these ratios for Planckian radiators with corresponding color temperatures.

Fig. 8
Fig. 8

Ratios of near-infrared (780–1100 nm) to visible (380–780 nm) irradiance as a function of inverse CCT (in MK-1). The solid curve shows these ratios for Planckian radiators with corresponding color temperatures.

Fig. 9
Fig. 9

(a) Spectral distribution from 300–1100 nm of eigenvectors V1(λ), V2(λ), and V3(λ) for our Granada daylight basis set. Solid curve, i=1 eigenvector V1(λ) [the mean E(λ)]; dashed curve, i=2 eigenvector V2(λ); dotted curve, i=3 eigenvector V3(λ). (b) Spectral distribution from 300 to 1100 nm of eigenvectors V4(λ), V5(λ), and V6(λ) for our Granada daylight basis set. Solid curve, i=4 eigenvector V4(λ); dashed curve, i=5 eigenvector V5(λ); dotted curve, i=6 eigenvector V6(λ).

Fig. 10
Fig. 10

Colorimetric characteristics of the eigenvectors shown in Fig. 10(a), with the chromaticity of the mean vector V1(λ) marked “+.” For V2(λ) and V3(λ) we plot the chromaticity shift that each accounts for (lines with arrows). We also include the deuteranopic and tritanopic confusion lines (skewed grid lines) as well as the Planckian (dashed curve).

Fig. 11
Fig. 11

Mean GFC for our 2600 Granada daylight spectra, with use of 2p10 eigenvectors in Eq. (2) for the indicated spectral region. We label in parentheses the number of spectral irradiances within each region for 5-nm resolution.

Fig. 12
Fig. 12

Mean CIELUV color difference ΔEuv* (Eq. 4) as a function of mean GFC. Numbers next to the squares indicate the number of eigenvectors p needed in Eq. (2) to obtain the given GFC. Each error bar spans 2 standard deviations.

Tables (4)

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Table 1 Most-Frequent Inverse CCT Intervals m(CCT) as Measured by Various Researchers

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Table 2 Classification of our Granada Daylight Spectra by Sky State

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Table 3 Spectral Regions of Our 2600 Granada Daylight Spectraa

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Table 4 Percentage of Reconstructed Spectra ER(λ) That Exceed Our Three Target GFC Values As a Function of Spectral Region and Number of Eigenvectors p Used in Eq. (2) (Here, 2p8)a

Equations (4)

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y=-0.05188+1.55320x-1.09234x2.
ER(λ)=i=1pEE(λ)|Vi(λ)Vi(λ),
GFC=|Σj EE(λj)ER(λj)||Σj [EE(λj)]2|1/2|Σj [ER(λj)]2|1/2.
ΔEuv*=[(ΔL*)2+(Δu*)2+(Δv*)2]1/2,

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