Abstract

A device for the convenient quantitative measurement of the thermal radiation from the atmosphere has been developed. In the instrument the emission spectrum of the earth’s atmosphere as observed at ground level is compared automatically with a spectrum approximating that of a blackbody at the boiling point of liquid nitrogen at atmospheric pressure. The most prominent features of the atmospheric spectrum between 4 μ and 15.5 μ, observed during daylight and darkness when the sky is clear, are due to emission by carbon dioxide, ozone, and water vapor; the intensity of the water vapor emission shows pronounced variations with atmospheric temperature and humidity. The spectrum of an overcast sky resembles that of a blackbody. By comparing the recorder traces of the atmospheric spectra with similar traces obtained with a blackbody source, it is possible to estimate the effective radiation temperature of various portions of the sky for various atmospheric conditions.

© 1955 Optical Society of America

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References

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  1. Compendium of Meteorology, Am. Met. Soc. (Boston, Massachusetts), 34–49 (1951).
  2. J. Strong, J. Frank. Inst. 232, 1 (1941); J. Opt. Soc. Am. 29, 520 (1939).
    [Crossref]
  3. A. Adel, Astrophys. J. 103, 19 (1946); Astrophys. J. 105, 406 (1947). Cent. Proc. Roy. Meteor. Soc. (London) p. 5 (1950).
    [Crossref]
  4. The term “effective radiation temperature” is used in a somewhat different sense by Adel (see reference 2).
  5. C. P. Butler, “On the Exchange of Radiant Energy Between the Earth and Sky,” , June11, 1952.
  6. For a liquid nitrogen blackbody, Rλ is 0.3 percent Rλ for a 0°C blackbody at 15 microns and still less at shorter wavelengths.
  7. Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
    [Crossref]
  8. Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
    [Crossref]

1952 (2)

Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
[Crossref]

Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
[Crossref]

1951 (1)

Compendium of Meteorology, Am. Met. Soc. (Boston, Massachusetts), 34–49 (1951).

1946 (1)

A. Adel, Astrophys. J. 103, 19 (1946); Astrophys. J. 105, 406 (1947). Cent. Proc. Roy. Meteor. Soc. (London) p. 5 (1950).
[Crossref]

1941 (1)

J. Strong, J. Frank. Inst. 232, 1 (1941); J. Opt. Soc. Am. 29, 520 (1939).
[Crossref]

Adel, A.

A. Adel, Astrophys. J. 103, 19 (1946); Astrophys. J. 105, 406 (1947). Cent. Proc. Roy. Meteor. Soc. (London) p. 5 (1950).
[Crossref]

Benedict,

Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
[Crossref]

Butler, C. P.

C. P. Butler, “On the Exchange of Radiant Energy Between the Earth and Sky,” , June11, 1952.

Claassen,

Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
[Crossref]

Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
[Crossref]

Oxholm,

Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
[Crossref]

Shaw,

Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
[Crossref]

Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
[Crossref]

Strong, J.

J. Strong, J. Frank. Inst. 232, 1 (1941); J. Opt. Soc. Am. 29, 520 (1939).
[Crossref]

Am. Met. Soc. (Boston, Massachusetts) (1)

Compendium of Meteorology, Am. Met. Soc. (Boston, Massachusetts), 34–49 (1951).

Astrophys. J. (2)

Shaw, Oxholm, and Claassen, Astrophys. J. 116, 554 (1952).
[Crossref]

A. Adel, Astrophys. J. 103, 19 (1946); Astrophys. J. 105, 406 (1947). Cent. Proc. Roy. Meteor. Soc. (London) p. 5 (1950).
[Crossref]

J. Frank. Inst. (1)

J. Strong, J. Frank. Inst. 232, 1 (1941); J. Opt. Soc. Am. 29, 520 (1939).
[Crossref]

J. Research Natl. Bur. Standards (1)

Benedict, Claassen, and Shaw, J. Research Natl. Bur. Standards 49, 91–132 (1952).
[Crossref]

Other (3)

The term “effective radiation temperature” is used in a somewhat different sense by Adel (see reference 2).

C. P. Butler, “On the Exchange of Radiant Energy Between the Earth and Sky,” , June11, 1952.

For a liquid nitrogen blackbody, Rλ is 0.3 percent Rλ for a 0°C blackbody at 15 microns and still less at shorter wavelengths.

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Figures (4)

Fig. 1
Fig. 1

Optical arrangement for automatic comparison of the sky spectrum with the spectrum of a “blackbody” at liquid nitrogen temperatures.

Fig. 2
Fig. 2

Optical arrangement for directing sky radiation to the spectrograph.

Fig. 3
Fig. 3

Typical zenith sky spectra with a solar spectrum for comparison. The dashed curve above each tracing was obtained with a laboratory blackbody of temperature TB. The “ground temperature” T0 was measured by automatic recording in a standard screen. Water-vapor concentrations (g/m3) six feet above ground level have the following values for various parts of the figure: (b)9.3, (c)8.0, (d)5.9, (e)15.2, and (f)20.3.

Fig. 4
Fig. 4

Spectra observed at various zenith distances on a clear night. The upper curve gives a solar spectrum for comparison.

Equations (3)

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D B λ T = K λ R B λ T ,
R S λ = D S λ / K λ .
R S = R S λ d λ