Abstract

The influence of ground level temperature and humidity on the intensity and spectral distribution of the thermal radiation reaching ground level from the clear sky has been investigated in the spectral region between 4μ and 15μ. The influence of the thickness of the emitting layer or atmospheric path viewed by the detector has also been studied by making measurements of the sky radiation from various zenith distances. Empirical relationships between the intensity of the atmospheric emission spectrum in various spectral intervals and the ground-level conditions of temperature and humidity are developed and presented in graphical form.

© 1956 Optical Society of America

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References

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  1. Sloan, Shaw, and Williams, J. Opt. Soc. Am. 45, 455 (1955).
    [CrossRef]
  2. F. W. Paul Götz, Compendium of Meteorology (American Meteorological Society, Boston, 1951), p. 275.
  3. W. M. Elsasser, Harvard Met. Studies No. 6. (Harvard University Printing Office, Cambridge, Massachusetts1942).
  4. J. Strong, J. Franklin Inst. 232, 2 (1941); J. N. Howard and et al., J. Opt. Soc. Am. (to be published).
    [CrossRef]
  5. R. N. Goody, Quart. J. Roy. Meteorol. Soc. 78, 165 (1952).
    [CrossRef]
  6. Howard, Burch, and Williams (to be published).
  7. A. Adel. , 1949. Air Force Cambridge Center Laboratories, Cambridge, Massachusetts.

1955 (1)

1952 (1)

R. N. Goody, Quart. J. Roy. Meteorol. Soc. 78, 165 (1952).
[CrossRef]

1941 (1)

J. Strong, J. Franklin Inst. 232, 2 (1941); J. N. Howard and et al., J. Opt. Soc. Am. (to be published).
[CrossRef]

Adel, A.

A. Adel. , 1949. Air Force Cambridge Center Laboratories, Cambridge, Massachusetts.

Burch,

Howard, Burch, and Williams (to be published).

Elsasser, W. M.

W. M. Elsasser, Harvard Met. Studies No. 6. (Harvard University Printing Office, Cambridge, Massachusetts1942).

Goody, R. N.

R. N. Goody, Quart. J. Roy. Meteorol. Soc. 78, 165 (1952).
[CrossRef]

Howard,

Howard, Burch, and Williams (to be published).

Paul Götz, F. W.

F. W. Paul Götz, Compendium of Meteorology (American Meteorological Society, Boston, 1951), p. 275.

Shaw,

Sloan,

Strong, J.

J. Strong, J. Franklin Inst. 232, 2 (1941); J. N. Howard and et al., J. Opt. Soc. Am. (to be published).
[CrossRef]

Williams,

Sloan, Shaw, and Williams, J. Opt. Soc. Am. 45, 455 (1955).
[CrossRef]

Howard, Burch, and Williams (to be published).

J. Franklin Inst. (1)

J. Strong, J. Franklin Inst. 232, 2 (1941); J. N. Howard and et al., J. Opt. Soc. Am. (to be published).
[CrossRef]

J. Opt. Soc. Am. (1)

Quart. J. Roy. Meteorol. Soc. (1)

R. N. Goody, Quart. J. Roy. Meteorol. Soc. 78, 165 (1952).
[CrossRef]

Other (4)

Howard, Burch, and Williams (to be published).

A. Adel. , 1949. Air Force Cambridge Center Laboratories, Cambridge, Massachusetts.

F. W. Paul Götz, Compendium of Meteorology (American Meteorological Society, Boston, 1951), p. 275.

W. M. Elsasser, Harvard Met. Studies No. 6. (Harvard University Printing Office, Cambridge, Massachusetts1942).

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Figures (7)

Fig. 1
Fig. 1

Emissive power of the zenith sky RS(4μ, 15μ) compared with the ground level air temperature T0 during the 24-hour period, April 21, 1954.

Fig. 2
Fig. 2

Emissive power of the zenith sky for four small spectral intervals during the 24-hour period, April 21, 1954. Curve a represents RS(6.0μ, 7.0μ); curve b, RS(12.5μ, 13.0μ); curve c, RS(9.25μ, 10.0μ); curve d, RS(11.5μ, 12.0μ).

Fig. 3
Fig. 3

The ratio of the emissive power of the zenith sky RS(4μ, 15μ) to the corresponding emissive power RB(4μ, 15μ)T0 of a blackbody at ground level air temperature T0 plotted against the absolute humidity of the air at ground level. The dotted curve represents the general trend.

Fig. 4
Fig. 4

The ratio of the emissive power of the sky to the emissive power of a blackbody at ground level air temperature T0 plotted as a function of (atmospheric path viewed)1/2; the spectral intervals involved are indicated in the various parts of the figure. The data represented were obtained in the interval 2200–0230 hours, September 23–24, 1954.

Fig. 5
Fig. 5

Each of the upper curves shows the sky’s emissive power RS12) as a function of zenith distance. Each of the lower curves gives a corresponding plot of the quantity πRS12) sin2Z as a function of zenith distance. The area under each lower curve represents the total radiant flux per unit horizontal area at ground level from the entire sky in the indicated wavelength interval λ1 to λ2. (The data are the same as those plotted in a different manner in Fig. 4).

Fig. 6
Fig. 6

The ratio of the total radiation flux from the sky to the corresponding flux from a blackbody at ground level air temperature in the region 4μ to 15μ plotted against the absolute humidity of ground level air. The dotted curve gives the general trend.

Fig. 7
Fig. 7

The ratio of the total radiation flux from the sky to the corresponding flux from a blackbody at ground level air temperature for various spectral regions plotted against the absolute humidity of ground level air. The dotted curve gives the general trend for each wavelength interval. Curve a gives the trend for the interval 8.0μ to 8.5μ; Curve b, 10.75μ to 11.0μ; Curve c, 12.5μ to 13.0μ; Curve d, 11.5μ to 12.0μ.

Tables (1)

Tables Icon

Table I Resume of zenith sky data.

Equations (4)

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R S λ = D S λ / K λ ,
R S ( λ 1 , λ 2 ) = λ 1 λ 2 R S λ d λ = λ 1 λ 2 D S λ K λ d λ ,
l = sec Z .
Σ S ( λ 1 , λ 2 ) = 0 π / 2 R S ( λ 1 , λ 2 ) 2 π sin Z cos Z d Z ; Σ S ( λ 1 , λ 2 ) = 0 π / 2 π R S ( λ 1 , λ 2 ) sin 2 Z d Z .