Abstract

Spectra of the real and imaginary parts of the refractive index m = n′ − in″ from 2.5 μm to 40 μm of ammonium sulfate, Sahara dust (as collected at Barbados), volcanic dust (pumice), and dust from a coal-fired power plant are presented. With a peak absorption index n″ = 1.0 at 10 μm Sahara dust turns out to be the strongest absorber in the atmospheric window. The dispersion of n′ is also very pronounced near 9 μm and 20 μm. Volcanic and coal-fire dust also absorb in the window region stronger than most of our earlier-investigated more normal aerosol fractions. The data for ammonium sulfate are compared with Remsberg’s measurements on an aqueous solution.

© 1973 Optical Society of America

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References

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  1. F. E. Volz, J. Geophys. Res. 77, 1017 (1972).
    [CrossRef]
  2. F. E. Volz, Appl. Opt. 11, 755 (1972).
    [CrossRef] [PubMed]
  3. E. E. Remsberg, Radiative properties of several probable constituents of atmospheric aerosols. Thesis, University of Wisconsin (1971).
  4. J. M. Prospero, Bull. Am. Meteorol. Soc. 49, 645 (1968); T. N. Carlson, J. M. Prospero, J. Appl. Meteorol. 11, 283 (1972).
    [CrossRef]
  5. M. Czerny, Z. Phys. 65, 600 (1930).
    [CrossRef]
  6. J. C. Wilmot, Proc. Phys. Soc. 63, 389 (1950).
    [CrossRef]
  7. F. A. Miller, C. H. Wilkins, Anal. Chem. 24, 1253 (1952).
    [CrossRef]
  8. W. M. Irvine, J. B. Pollack, Icarus 8, 3241968).
    [CrossRef]
  9. R. Chester, L. R. Johnson, Nature 229, 105 (1971).
    [CrossRef] [PubMed]
  10. F. W. Wright, P. W. Hodge, Smithsonian Institution, Astrophysical Observations, Research in Space Science, Special Report 172 (Cambridge, Mass., 1965).
  11. A. Cohen, NOAA-ITSA, Boulder, Colo; personal communication (1972).
  12. F. E. Volz, “Infrared scattering and absorption by atmospheric aerosol,” in preparation (1973).

1972 (2)

F. E. Volz, J. Geophys. Res. 77, 1017 (1972).
[CrossRef]

F. E. Volz, Appl. Opt. 11, 755 (1972).
[CrossRef] [PubMed]

1971 (1)

R. Chester, L. R. Johnson, Nature 229, 105 (1971).
[CrossRef] [PubMed]

1968 (2)

W. M. Irvine, J. B. Pollack, Icarus 8, 3241968).
[CrossRef]

J. M. Prospero, Bull. Am. Meteorol. Soc. 49, 645 (1968); T. N. Carlson, J. M. Prospero, J. Appl. Meteorol. 11, 283 (1972).
[CrossRef]

1952 (1)

F. A. Miller, C. H. Wilkins, Anal. Chem. 24, 1253 (1952).
[CrossRef]

1950 (1)

J. C. Wilmot, Proc. Phys. Soc. 63, 389 (1950).
[CrossRef]

1930 (1)

M. Czerny, Z. Phys. 65, 600 (1930).
[CrossRef]

Chester, R.

R. Chester, L. R. Johnson, Nature 229, 105 (1971).
[CrossRef] [PubMed]

Cohen, A.

A. Cohen, NOAA-ITSA, Boulder, Colo; personal communication (1972).

Czerny, M.

M. Czerny, Z. Phys. 65, 600 (1930).
[CrossRef]

Hodge, P. W.

F. W. Wright, P. W. Hodge, Smithsonian Institution, Astrophysical Observations, Research in Space Science, Special Report 172 (Cambridge, Mass., 1965).

Irvine, W. M.

W. M. Irvine, J. B. Pollack, Icarus 8, 3241968).
[CrossRef]

Johnson, L. R.

R. Chester, L. R. Johnson, Nature 229, 105 (1971).
[CrossRef] [PubMed]

Miller, F. A.

F. A. Miller, C. H. Wilkins, Anal. Chem. 24, 1253 (1952).
[CrossRef]

Pollack, J. B.

W. M. Irvine, J. B. Pollack, Icarus 8, 3241968).
[CrossRef]

Prospero, J. M.

J. M. Prospero, Bull. Am. Meteorol. Soc. 49, 645 (1968); T. N. Carlson, J. M. Prospero, J. Appl. Meteorol. 11, 283 (1972).
[CrossRef]

Remsberg, E. E.

E. E. Remsberg, Radiative properties of several probable constituents of atmospheric aerosols. Thesis, University of Wisconsin (1971).

Volz, F. E.

F. E. Volz, J. Geophys. Res. 77, 1017 (1972).
[CrossRef]

F. E. Volz, Appl. Opt. 11, 755 (1972).
[CrossRef] [PubMed]

F. E. Volz, “Infrared scattering and absorption by atmospheric aerosol,” in preparation (1973).

Wilkins, C. H.

F. A. Miller, C. H. Wilkins, Anal. Chem. 24, 1253 (1952).
[CrossRef]

Wilmot, J. C.

J. C. Wilmot, Proc. Phys. Soc. 63, 389 (1950).
[CrossRef]

Wright, F. W.

F. W. Wright, P. W. Hodge, Smithsonian Institution, Astrophysical Observations, Research in Space Science, Special Report 172 (Cambridge, Mass., 1965).

Anal. Chem. (1)

F. A. Miller, C. H. Wilkins, Anal. Chem. 24, 1253 (1952).
[CrossRef]

Appl. Opt. (1)

Bull. Am. Meteorol. Soc. (1)

J. M. Prospero, Bull. Am. Meteorol. Soc. 49, 645 (1968); T. N. Carlson, J. M. Prospero, J. Appl. Meteorol. 11, 283 (1972).
[CrossRef]

Icarus (1)

W. M. Irvine, J. B. Pollack, Icarus 8, 3241968).
[CrossRef]

J. Geophys. Res. (1)

F. E. Volz, J. Geophys. Res. 77, 1017 (1972).
[CrossRef]

Nature (1)

R. Chester, L. R. Johnson, Nature 229, 105 (1971).
[CrossRef] [PubMed]

Proc. Phys. Soc. (1)

J. C. Wilmot, Proc. Phys. Soc. 63, 389 (1950).
[CrossRef]

Z. Phys. (1)

M. Czerny, Z. Phys. 65, 600 (1930).
[CrossRef]

Other (4)

E. E. Remsberg, Radiative properties of several probable constituents of atmospheric aerosols. Thesis, University of Wisconsin (1971).

F. W. Wright, P. W. Hodge, Smithsonian Institution, Astrophysical Observations, Research in Space Science, Special Report 172 (Cambridge, Mass., 1965).

A. Cohen, NOAA-ITSA, Boulder, Colo; personal communication (1972).

F. E. Volz, “Infrared scattering and absorption by atmospheric aerosol,” in preparation (1973).

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Figures (4)

Fig. 1
Fig. 1

Real (a) and imaginary (b) part of the refractive index of solid ammonium sulfate (—), 35% aqueous solution (- - -, Ref. 3), and water (⋯). Dashes indicate the absorption index obtained for different pellet concentrations (a, 0.05 mg cm−2; b, 0.50 mg cm−2; c, 5.0 mg cm−2). Arrows indicate the band positions according to Miller and Wilkins.7 The dashed branches in (b) refer to observed reflectance (right-hand ordinate) before correction for n″.

Fig. 2
Fig. 2

Transmittance of a coarse powder of ammonium sulfate. Interference pattern and the few absorption bands of the supporting polyethylene film were omitted. The cause of the 3,4-μm absorption is not clear.

Fig. 3
Fig. 3

Optical constants n′ and n″ of Sahara dust as compared with those of aerosol water-solubles, and n″ of volcanic dust and flyash. The dotted part of the n′ curve of Sahara dust refers to observed reflectance [n′ = (1 + R)/(1 − R)] before correction for n″.

Fig. 4
Fig. 4

Wavelength dependence of extinction and scattering coefficients for Sahara dust and dust from precipitation. At 9 μm, the effect of different values of n″ is shown for dust from rainwater. Values of 0.45 μm for n′ = 1.50, n″ = 0.01 are = σE 9.44 × 10−8 m−1, σSC = 8.74 × 10−8 m−1.

Equations (1)

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n = [ ( 1 + R ) / ( 1 - R ) ] ± { [ 4 R / ( 1 - R ) 2 ] - n 2 } 1 2 .

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