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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 28, Iss. 7 — Jul. 1, 1938
  • pp: 227–236

The Brightness of the Twilight Sky and the Density and Temperature of the Atmosphere

E. O. HULBURT  »View Author Affiliations

JOSA, Vol. 28, Issue 7, pp. 227-236 (1938)

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With a calibrated Macbeth illuminometer measurements were made of iz the brightness of the zenith sky and of ig the energy flux across a vertical plane from the twilight horizon for the depression θ of the sun below the horizon from 0° to 13°. For clear sky conditions the iz, θ and ig, θ curves did not change within 30 percent with the season from October, 1937, to April, 1938, and were the same for evening and morning twilight. Calculation from the Rayleigh theory of molecular scattering and the observed iz and ig data showed that within ±30 percent the densities of the atmosphere from sea level to about 60 km were those of the density-height relation known to 20 km and extrapolated for a temperature of 218°K. It follows that the temperature of the twilight temperate zone atmosphere is 218°±15°K from 20 to 60 km. The influence of secondary scattering, determined from ig, although small for small values of θ increased rapidly with θ to such an extent that the twilight zenith sky brightness measures gave no indication of the distribution of density above about 60 km.

E. O. HULBURT, "The Brightness of the Twilight Sky and the Density and Temperature of the Atmosphere," J. Opt. Soc. Am. 28, 227-236 (1938)

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  1. Hulburt, J. O. S. A. 27, 377 (1937).
  2. Fessenkoff, Astrophysical Observatory, Moscow, Publications, 2, 113 (1923) (Résumé in French, pages 113–123; complete paper in Russian, pages 7–113).
  3. Link, Comptes rendus 199, 303 (1934); 200, 78 (1935).
  4. Measures of twilight sky brightness are recorded by Kimball and Thiessen, Monthly Weather Review 44, 614 (1916); by Bauer, Danjon and Langevin, Comptes rendus 172, 2115 (1924); by Dufay, Bulletin Observatoire de Lyons, 10, No. 9 (1928); and by Smart, Mon. Not. Roy. Ast. Soc. 93, 441 (1932–33)
  5. The lamp as standardized at the National Bureau of Standards by Dr. H. T. Wensell.
  6. Reference 1, Table II.
  7. Humphreys, Physics of the Air, second edition (1929) p. 74.
  8. Rayleigh, Phil. Mag. 51, 107, 274 (1871); 47, 375 (1899).
  9. Meggers and Peters, Bul. Nat. Bur. Stand. 14, 731 (1918).
  10. Smithsonian Physical Tables (1933), p. 608.
  11. The exact paths of rays through the atmosphere have been calculated by J. Sweer of this laboratory. His work will appear in a separate paper.
  12. Raman, Molecular Scattering of Light (1922), p. 39, indicated that he had attempted to formulate a quantitative theory of the intensity of twilight without, however, complete success.
  13. For example, Wegener, Lehrbuch der Physik, Vol. 5 (Müller-Pouillets, 1938), p. 228.
  14. Maris, Terr. Mag. 33, 233 (1928); 34, 45 (1929).
  15. Martyn and Pulley, Proc. Roy. Soc. 154, 455 (1936), argued that the temperature increased from about 220°K at 40 km to above 400° at 70 km. See also Godfrey and Price, Proc. Roy. Soc. 163, 228 (1937), and Kidson, Roy. Met. Soc., Quart. Jr., 63, 477 (1937).
  16. Shepherd, National Geographic Society—U. S. Army Air Corps Stratosphere Flight of 1935. Technical Papers, p. 117 (1936); Regner, Nature 138, 544 (1936); Lepape and Colange, Nature 137, 459 (1936); Paneth and Gluckauf, Nature 136, 717 (1935); Prokofiew and Glotzman, Nature 133, 918 (1934).
  17. Hulburt, Phys. Rev. 38, 1876 (1931).
  18. Fowle, Smithsonian Miscellaneous Collections 69, 3 (1918).
  19. Slipher, Lowell Observatory Circular, February 20, 1931; Mon. Not. Roy. Ast. Soc. 93, 657 (1932–1933).

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