Abstract

The absolute intensity, color, and polarization of the sky were measured during the eclipse of 30 June 1973 in Northern Kenya. Zenith sky radiance during totality decreased by a factor of 104 from the normal day sky value. The distribution of sky intensity with angle on the celestial hemisphere was approximately symmetrical about the local zenith, with this point having the minimum intensity value. The spectral distribution of zenithal diffuse skylight shifted toward the blue during totality, but the horizon reddened. The polarization ratio P decreased from a normal day value of 0.45 to 0.04. There is evidence that the distribution of polarization ratio is strongly affected by variations in surface albedo. The major results are compatible with predictions based on a radiative transfer model that considers double-scattering processes only.

© 1975 Optical Society of America

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References

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  1. S. M. Silverman, E. G. Mullen, “Sky Brightness during Eclipses: A Compendium from the Literature,” unpublished, June1972.
  2. W. E. Sharp, J. W. Lloyd, S. M. Silverman, Appl. Opt. 5, 787 (1966).
    [CrossRef] [PubMed]
  3. W. E. Sharp, S. M. Silverman, J. W. F. Lloyd, Appl. Opt. 10, 1207 (1971).
    [CrossRef] [PubMed]
  4. B. S. Dandekar, J. P. Turtle, Appl. Opt. 10, 1220 (1971).
    [CrossRef] [PubMed]
  5. W. N. Hall, Appl. Opt. 10, 1225 (1971).
    [CrossRef] [PubMed]
  6. J. W. F. Lloyd, S. M. Silverman, Appl. Opt. 10, 1220 (1971).
    [CrossRef]
  7. C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
    [CrossRef]
  8. J. G. Moore, D. Lamb, Annal. Geophys. 23, 339 (1967).
  9. G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
    [CrossRef]
  10. K. L. Coulson, J. V. Dave, Z. Sekera, Tables Related to Radiation Emerging from a Planetary Atmosphere with Rayleigh Scattering (University of California Press, Berkeley1960), p. 548.
  11. J. G. Moore, C. R. Rao, Annal. Geophys. 22, 147 (1966).
  12. C. S. Deehr, M. H. Rees, Planet. Space Sci. 12, 875 (1964).
    [CrossRef]
  13. E. deBary, Appl. Opt. 3, 1293 (1964).
    [CrossRef]
  14. K. Ya. Kondratiev, in Radiation in the Atmosphere, International Geophysics Series, J. Van Miegham, Ed. (Academic, New York, 1969), Vol. 12.
  15. K. Bullrich, “Scattered Radiation in the Atmosphere,” in Advances in Geophysics (Academic, New York, 1966).
  16. B. S. Dandekar, Appl. Opt. 7, 705 (1968).
    [CrossRef] [PubMed]
  17. G. E. Shaw, C. S. Deehr, “On the Relation Between Circumsolar Sky Brightness and Atmospheric Aerosol,” EPA Report (1974), in press.

1973

G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
[CrossRef]

1972

C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
[CrossRef]

1971

1968

1967

J. G. Moore, D. Lamb, Annal. Geophys. 23, 339 (1967).

1966

1964

C. S. Deehr, M. H. Rees, Planet. Space Sci. 12, 875 (1964).
[CrossRef]

E. deBary, Appl. Opt. 3, 1293 (1964).
[CrossRef]

Bullrich, K.

K. Bullrich, “Scattered Radiation in the Atmosphere,” in Advances in Geophysics (Academic, New York, 1966).

Coulson, K. L.

K. L. Coulson, J. V. Dave, Z. Sekera, Tables Related to Radiation Emerging from a Planetary Atmosphere with Rayleigh Scattering (University of California Press, Berkeley1960), p. 548.

Dandekar, B. S.

Dave, J. V.

K. L. Coulson, J. V. Dave, Z. Sekera, Tables Related to Radiation Emerging from a Planetary Atmosphere with Rayleigh Scattering (University of California Press, Berkeley1960), p. 548.

deBary, E.

Deehr, C. S.

C. S. Deehr, M. H. Rees, Planet. Space Sci. 12, 875 (1964).
[CrossRef]

G. E. Shaw, C. S. Deehr, “On the Relation Between Circumsolar Sky Brightness and Atmospheric Aerosol,” EPA Report (1974), in press.

Hall, W. N.

Herman, B. M.

G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
[CrossRef]

Kondratiev, K. Ya.

K. Ya. Kondratiev, in Radiation in the Atmosphere, International Geophysics Series, J. Van Miegham, Ed. (Academic, New York, 1969), Vol. 12.

Lamb, D.

J. G. Moore, D. Lamb, Annal. Geophys. 23, 339 (1967).

Lloyd, J. W.

Lloyd, J. W. F.

Moore, J. G.

C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
[CrossRef]

J. G. Moore, D. Lamb, Annal. Geophys. 23, 339 (1967).

J. G. Moore, C. R. Rao, Annal. Geophys. 22, 147 (1966).

Mullen, E. G.

S. M. Silverman, E. G. Mullen, “Sky Brightness during Eclipses: A Compendium from the Literature,” unpublished, June1972.

Rao, C. R.

C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
[CrossRef]

J. G. Moore, C. R. Rao, Annal. Geophys. 22, 147 (1966).

Reagan, J. A.

G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
[CrossRef]

Rees, M. H.

C. S. Deehr, M. H. Rees, Planet. Space Sci. 12, 875 (1964).
[CrossRef]

Sekera, Z.

K. L. Coulson, J. V. Dave, Z. Sekera, Tables Related to Radiation Emerging from a Planetary Atmosphere with Rayleigh Scattering (University of California Press, Berkeley1960), p. 548.

Sharp, W. E.

Shaw, G. E.

G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
[CrossRef]

G. E. Shaw, C. S. Deehr, “On the Relation Between Circumsolar Sky Brightness and Atmospheric Aerosol,” EPA Report (1974), in press.

Silverman, S. M.

Takashima, T.

C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
[CrossRef]

Turtle, J. P.

Annal. Geophys.

J. G. Moore, D. Lamb, Annal. Geophys. 23, 339 (1967).

J. G. Moore, C. R. Rao, Annal. Geophys. 22, 147 (1966).

Appl. Opt.

J. Appl. Meteorol.

G. E. Shaw, J. A. Reagan, B. M. Herman, J. Appl. Meteorol. 12, 374 (1973).
[CrossRef]

J. Atmos. Terrestrial Phys.

C. R. Rao, T. Takashima, J. G. Moore, J. Atmos. Terrestrial Phys. 34, 573 (1972).
[CrossRef]

Planet. Space Sci.

C. S. Deehr, M. H. Rees, Planet. Space Sci. 12, 875 (1964).
[CrossRef]

Other

K. L. Coulson, J. V. Dave, Z. Sekera, Tables Related to Radiation Emerging from a Planetary Atmosphere with Rayleigh Scattering (University of California Press, Berkeley1960), p. 548.

G. E. Shaw, C. S. Deehr, “On the Relation Between Circumsolar Sky Brightness and Atmospheric Aerosol,” EPA Report (1974), in press.

K. Ya. Kondratiev, in Radiation in the Atmosphere, International Geophysics Series, J. Van Miegham, Ed. (Academic, New York, 1969), Vol. 12.

K. Bullrich, “Scattered Radiation in the Atmosphere,” in Advances in Geophysics (Academic, New York, 1966).

S. M. Silverman, E. G. Mullen, “Sky Brightness during Eclipses: A Compendium from the Literature,” unpublished, June1972.

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Figures (11)

Fig. 1
Fig. 1

Map of the area around Loiyengalani Oasis, Kenya, showing the intersection of the umbra with the ground and with a horizontal plane located at an altitude of 50 km at midtotality.

Fig. 2
Fig. 2

Sky radiance at 400 nm (ordinate values = πI/F0) in the solar vertical during totality. Numerals refer to measurement times (in seconds) from second contact.

Fig. 3
Fig. 3

Sky radiance πI/F0 at 600 nm in the solar vertical during totality.

Fig. 4
Fig. 4

Sky radiance πI/F0 at 400 nm in a vertical plane perpendicular to the solar vertical during totality.

Fig. 5
Fig. 5

Sky radiance πI/F0 at 600 nm in a vertical plane perpendicular to the solar vertical plane during totality.

Fig. 6
Fig. 6

Sky radiance πI/F0 at 400 nm (solid) and 600 nm (dashed) in the solar vertical during the partial phase of the eclipse.

Fig. 7
Fig. 7

Sky radiance πI/F0 as a function of solar geometric obscuration ratio at 400 nm (solid) and 600 nm (dashed). Sky radiance during normal noneclipsed conditions (λ = 600 nm) is shown for comparison.

Fig. 8
Fig. 8

Zenith sky radiance πI/F0 at 445 nm during the totality.

Fig. 9
Fig. 9

Sky polarization ratio at 400 nm in the solar vertical 90° from the sun.

Fig. 10
Fig. 10

Sky polarization ratio at 400 nm in the solar vertical during pretotality (solid) and totality (dotted).

Fig. 11
Fig. 11

(a) Spectral distribution of zenith sky radiance πI/F0 at solar noon on 30 June 1973. Calculated radiance resulting from scattering in pure molecular atmosphere (τ = τR) and for scattering in an atmosphere with τ = τR + τD are illustrated. (b) Spectral distribution of zenith sky radiance during midtotality.

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