Abstract

An experimental investigation was carried out to determine possible differences in visible light extinction properties of continental and maritime air. Urban, desert, and oceanic atmospheres were probed by means of a stable photodiode radiometer using direct sunlight as the source. No major differences were found for the three locations. Experimental coefficients generally lie slightly below model data, though significantly higher than would be expected from purely molecular scattering. Day-to-day variations of up to 40% were found to be nearly constant over the entire visible spectrum. Results of similar extinction measurements on thin cirrus clouds show a slight increase in scattering coefficient in going from 4000 Å to 7000 Å wavelength.

© 1968 Optical Society of America

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References

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  1. C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
    [CrossRef]
  2. L. Elterman, Atmospheric Attenuation Model, 1964, in the Ultraviolet, Visible and Infrared Regions for Altitudes to 50 km, Rep. AFCRL–67–740, Air Force Cambridge Research Laboratories (1964).
  3. H. W. Halsey, E. L. Gray, Determination of Atmospheric Transmissivity From Laser Backscatter Measurements, General Electric TIS Rep. No. R66SD44, August1966.
  4. The Nautical Almanac, 1967 and 1968, Nautical Almanac Office, U.S. Naval Observatory (U.S. Government Printing Office, Washington, D.C., 1966 and 1967).
  5. C. W. Allen, Astrophysical Quantities (The Athlone Press, London, 1955), p. 120.
  6. S. S. Penner, Quantitative Molecular Spectroscopy and Gas Emissivities (Addison-Wesley, Reading, Mass., 1959), pp. 12–14.
  7. H. R. Byers, General Meteorology (McGraw-Hill Book Company, Inc., New York, 1944), pp. 107–111.

1961 (1)

C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
[CrossRef]

Allen, C. W.

C. W. Allen, Astrophysical Quantities (The Athlone Press, London, 1955), p. 120.

Byers, H. R.

H. R. Byers, General Meteorology (McGraw-Hill Book Company, Inc., New York, 1944), pp. 107–111.

Chagnon, C. W.

C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
[CrossRef]

Elterman, L.

L. Elterman, Atmospheric Attenuation Model, 1964, in the Ultraviolet, Visible and Infrared Regions for Altitudes to 50 km, Rep. AFCRL–67–740, Air Force Cambridge Research Laboratories (1964).

Gray, E. L.

H. W. Halsey, E. L. Gray, Determination of Atmospheric Transmissivity From Laser Backscatter Measurements, General Electric TIS Rep. No. R66SD44, August1966.

Halsey, H. W.

H. W. Halsey, E. L. Gray, Determination of Atmospheric Transmissivity From Laser Backscatter Measurements, General Electric TIS Rep. No. R66SD44, August1966.

Junge, C.

C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
[CrossRef]

Manson, J. E.

C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
[CrossRef]

Penner, S. S.

S. S. Penner, Quantitative Molecular Spectroscopy and Gas Emissivities (Addison-Wesley, Reading, Mass., 1959), pp. 12–14.

J. Meteorol. (1)

C. Junge, C. W. Chagnon, J. E. Manson, J. Meteorol. 18, 81 (1961).
[CrossRef]

Other (6)

L. Elterman, Atmospheric Attenuation Model, 1964, in the Ultraviolet, Visible and Infrared Regions for Altitudes to 50 km, Rep. AFCRL–67–740, Air Force Cambridge Research Laboratories (1964).

H. W. Halsey, E. L. Gray, Determination of Atmospheric Transmissivity From Laser Backscatter Measurements, General Electric TIS Rep. No. R66SD44, August1966.

The Nautical Almanac, 1967 and 1968, Nautical Almanac Office, U.S. Naval Observatory (U.S. Government Printing Office, Washington, D.C., 1966 and 1967).

C. W. Allen, Astrophysical Quantities (The Athlone Press, London, 1955), p. 120.

S. S. Penner, Quantitative Molecular Spectroscopy and Gas Emissivities (Addison-Wesley, Reading, Mass., 1959), pp. 12–14.

H. R. Byers, General Meteorology (McGraw-Hill Book Company, Inc., New York, 1944), pp. 107–111.

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Figures (9)

Fig. 1
Fig. 1

Spectral transmission curves for bandpass filters used with radiometer whose normalized spectral response is shown by dashed curve.

Fig. 2
Fig. 2

Atmospheric transmission vs air mass at Valley Forge, Pa., on 6 November 1967, inferred by normalization at zero air mass. Straight lines were fitted to original radiometer current readings by disregarding data in the vicinity of clouds.

Fig. 3
Fig. 3

Radiometer signals (photocurrent) for direct sunlight recorded at Valley Forge on 6 February 1968. Below three air masses, data were taken in a.m. and p.m. skies.

Fig. 4
Fig. 4

Atmospheric extinction coefficient measured at Valley Forge compared with published model. Measurements were made on 6 November 1967 (○), 6 February 1968 (△), 19 February 1968 (□), and 17 April 1968 (×).

Fig. 5
Fig. 5

Atmospheric transmission vs air mass as measured at White Sands, 20 November 1967.

Fig. 6
Fig. 6

Atmospheric extinction coefficient, τ, measured at White Sands (Δ) compared with published model.

Fig. 7
Fig. 7

Radiometer signals (photocurrent) for direct sunlight recorded on Kwajalein Island, 5 January 1968. Zero air mass intercepts are from similar measurements with same instrument at Valley Forge on 6 February 1968. Dashed curves are straight line fits at indicated wavelengths.

Fig. 8
Fig. 8

Extinction coefficients of Kwajalein clear atmosphere (5 January 1968) and in the presence of specularly transmitting thin cirrus clouds compared with scattering models. Measurements were made on 5 January 1968 (○), 8 January (△), 12 January a.m. (□), 12 January p.m. (■), 15 January (×), and 17 January (●).

Fig. 9
Fig. 9

Extinction coefficients attributed to optically thin cirrus clouds observed at Kwajalein Island and referred to normal incidence. Variations in the magnitude of τ directly reflect differences in the optical thickness of the clouds observed on different days. Data refer to 8 January p.m. (●), 10 January p.m. (△), 12 January p.m. (○), 17 January p.m. (□), and 17 January p.m. (×).

Tables (2)

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Table I Coordinates of Measurement Sites

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Table II Long Term Stability of Radiometer Used in Atmospheric Measurements

Equations (1)

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I = I 0 e - τ w ,

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