Abstract

Two independent methods were used: direct spectrophotometry through the transparent windows of the atmospheric gases, and measurement of the number and diameter of the water droplets, followed by a Mie-theory calculation of the spectral transmittance. Results from the two methods are in good agreement when the media are sufficiently homogeneous, as for a quiet haze or fog and artificial smoke.

The following kinds of atmospheres were considered: hazes (optical density per km in the visible spectrum is less than 2); a small number of small-drop fogs (optical density per km less than 10); evolving fogs (which have changing distributions of drop-diameters); nonevolving, slightly selective fogs; artificial smokes. In addition, some information is given on the statistical distribution of drop-diameters.

It was found that the transmission of haze increased markedly with increasing wavelength, from the visible to 10 microns, but this marked increase was not found for fogs.

© 1957 Optical Society of America

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References

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  1. A. Arnulf and A. Bayle, Rev. opt. 28, 691 (1949).
  2. Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).
  3. Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).
  4. The question is fully discussed in W. E. K. Middleton’s excellent book, Vision through the Atmosphere (University of Toronto Press, Toronto, 1952).
  5. J. A. Stratton and H. G. Houghton, Phys. Rev. 38, 159 (1931).
    [CrossRef]
  6. H. G. Houghton and W. R. Chalker, J. Opt. Soc. Am. 39, 955 (1949).
    [CrossRef]
  7. J. C. Johnson, Physical Meteorology (Technology Press of Massachusetts Institute of Technology and John Wiley and Sons, Inc., New York, 1954).
  8. H. Dessens, Météorologie321 (1947).
  9. J. Terrien and F. Desvignes, Rev. opt. 27, 451 (1948).
  10. H. Gaertner, (U. S. Government Printing Office, Washington, D. C., 1947).
  11. J. Bricard, Physique des Nuages (Presses Universitaires de France, Paris, 1953).

1954 (1)

Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).

1950 (1)

Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).

1949 (2)

A. Arnulf and A. Bayle, Rev. opt. 28, 691 (1949).

H. G. Houghton and W. R. Chalker, J. Opt. Soc. Am. 39, 955 (1949).
[CrossRef]

1948 (1)

J. Terrien and F. Desvignes, Rev. opt. 27, 451 (1948).

1947 (1)

H. Dessens, Météorologie321 (1947).

1931 (1)

J. A. Stratton and H. G. Houghton, Phys. Rev. 38, 159 (1931).
[CrossRef]

Arnulf,

Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).

Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).

Arnulf, A.

A. Arnulf and A. Bayle, Rev. opt. 28, 691 (1949).

Bayle, A.

A. Arnulf and A. Bayle, Rev. opt. 28, 691 (1949).

Bricard,

Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).

Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).

Bricard, J.

J. Bricard, Physique des Nuages (Presses Universitaires de France, Paris, 1953).

Chalker, W. R.

Dessens, H.

H. Dessens, Météorologie321 (1947).

Desvignes, F.

J. Terrien and F. Desvignes, Rev. opt. 27, 451 (1948).

Gaertner, H.

H. Gaertner, (U. S. Government Printing Office, Washington, D. C., 1947).

Houghton, H. G.

H. G. Houghton and W. R. Chalker, J. Opt. Soc. Am. 39, 955 (1949).
[CrossRef]

J. A. Stratton and H. G. Houghton, Phys. Rev. 38, 159 (1931).
[CrossRef]

Johnson, J. C.

J. C. Johnson, Physical Meteorology (Technology Press of Massachusetts Institute of Technology and John Wiley and Sons, Inc., New York, 1954).

Middleton, W. E. K.

The question is fully discussed in W. E. K. Middleton’s excellent book, Vision through the Atmosphere (University of Toronto Press, Toronto, 1952).

Stratton, J. A.

J. A. Stratton and H. G. Houghton, Phys. Rev. 38, 159 (1931).
[CrossRef]

Terrien, J.

J. Terrien and F. Desvignes, Rev. opt. 27, 451 (1948).

Véret,

Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).

Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).

Compt. rend. (1)

Arnulf, Bricard, and Véret, Compt. rend. 230, 565 (1950) and Compt. rend. 238, 503 (1954).

J. Opt. Soc. Am. (1)

Météorologie (1)

H. Dessens, Météorologie321 (1947).

Phys. Rev. (1)

J. A. Stratton and H. G. Houghton, Phys. Rev. 38, 159 (1931).
[CrossRef]

Rev. opt. (3)

Arnulf, Bricard, and Véret, Rev. opt. 33, 658 (1954); Nuovo cimento, Ser. 10,  2(suppl.) 642 (1955).

J. Terrien and F. Desvignes, Rev. opt. 27, 451 (1948).

A. Arnulf and A. Bayle, Rev. opt. 28, 691 (1949).

Other (4)

H. Gaertner, (U. S. Government Printing Office, Washington, D. C., 1947).

J. Bricard, Physique des Nuages (Presses Universitaires de France, Paris, 1953).

The question is fully discussed in W. E. K. Middleton’s excellent book, Vision through the Atmosphere (University of Toronto Press, Toronto, 1952).

J. C. Johnson, Physical Meteorology (Technology Press of Massachusetts Institute of Technology and John Wiley and Sons, Inc., New York, 1954).

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Figures (14)

Fig. 1
Fig. 1

Infrared absorption regions for the atmospheric constituents water vapor, carbon dioxide, and ozone.

Fig. 2
Fig. 2

Diffusion function, after Houghton and Chalker.

Fig. 3
Fig. 3

Water droplets on spider threads.

Fig. 4
Fig. 4

Double-beam double-spectrophotometer arrangement.

Fig. 5
Fig. 5

Evolution of the transmission of a fog versus time, for various wavelengths.

Fig. 6
Fig. 6

Absorption by a haze.

Fig. 7
Fig. 7

Absorption by selective fogs.

Fig. 8
Fig. 8

Absorption by an evolving fog.

Fig. 9
Fig. 9

Absorption by stable fogs (1st type).

Fig. 10
Fig. 10

Absorption by stable fogs (2nd type).

Fig. 11
Fig. 11

Distribution of the radius of drops.

Fig. 12
Fig. 12

Distribution of the surfaces of drops.

Fig. 13
Fig. 13

Gaertner’s curves: absorption coefficient versus wavelength, for various drop radii.

Fig. 14
Fig. 14

Radius of the drops of monodispersed fogs having the same infrared selectivity as 90 natural fogs or hazes.

Tables (4)

Tables Icon

Table I Number and distribution of fogs and hazes studied.

Tables Icon

Table II List of the wavelengths used, in microns.

Tables Icon

Table III Characteristics of mirrors A of Fig. 4.

Tables Icon

Table IV Limits of the distance of perception (for a contrast threshold of 0.01) in meters, for haze and fogs, defined by their optical density d at a wavelength of 0.55 micron.

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

A = π r 2 K .
D = n A r log e .
D = π log e r 2 r 1 n Δ r r 2 K r .
n r = n r 2 r l V t = n r r · k ,
k = 3 4 π ρ · m r 1 r 2 r 2 n r ,
B 0 / B = 10 d x ,
S IR = D max - D 10 μ D max ,