Abstract

Superior mirages of unusual brightness are occasionally observed. Two such cases, photographed over the frozen surface of Lake Winnipeg, Canada, are documented. Visually, these mirages appear as featureless bright barriers far out on the lake. They are just images of the lake ice, yet the luminance in one case was 2.5 times (in the other, 1.7 times) the luminance of the ice surface in front of the mirage. The mirage itself can be modeled by means of a conduction inversion, but a proper explanation of the brightness is not yet available.

© 2003 Optical Society of America

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References

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  1. A. B. Fraser, W. H. Mach, “Mirages,” Sci. Am. 234, 102–111 (1976).
    [CrossRef]
  2. “Kodachrome 25, 64, and 200 Professional Film,” Kodak Publication E-55 (Eastman Kodak Company, Rochester, N.Y., 2001). The relevant data sheet is currently available on the Internet at http://www.kodak.com/global/en/professional/support/techPubs/e55/e55.shtml .
  3. W. A. Lyons, “Numerical simulation of Great Lakes conduction inversions,” in Proceedings of the 13th Conference on Great Lakes Research, State University College, Buffalo, N.Y., 1–3April1970, D. V. Anderson, J. S. Seddon, eds. (International Association for Great Lakes Research, Ann Arbor, Mich., 1970), pp. 369–387.
  4. M. Born, E. Wolf, Principles of Optics, 6th ed. (Pergamon, Oxford, UK, 1986), Sec. 4.8.
  5. W. H. Lehn, W. Friesen, “Simulation of mirages,” Appl. Opt. 31, 1267–1273 (1992).
    [CrossRef] [PubMed]

1992 (1)

1976 (1)

A. B. Fraser, W. H. Mach, “Mirages,” Sci. Am. 234, 102–111 (1976).
[CrossRef]

Born, M.

M. Born, E. Wolf, Principles of Optics, 6th ed. (Pergamon, Oxford, UK, 1986), Sec. 4.8.

Fraser, A. B.

A. B. Fraser, W. H. Mach, “Mirages,” Sci. Am. 234, 102–111 (1976).
[CrossRef]

Friesen, W.

Lehn, W. H.

Lyons, W. A.

W. A. Lyons, “Numerical simulation of Great Lakes conduction inversions,” in Proceedings of the 13th Conference on Great Lakes Research, State University College, Buffalo, N.Y., 1–3April1970, D. V. Anderson, J. S. Seddon, eds. (International Association for Great Lakes Research, Ann Arbor, Mich., 1970), pp. 369–387.

Mach, W. H.

A. B. Fraser, W. H. Mach, “Mirages,” Sci. Am. 234, 102–111 (1976).
[CrossRef]

Wolf, E.

M. Born, E. Wolf, Principles of Optics, 6th ed. (Pergamon, Oxford, UK, 1986), Sec. 4.8.

Appl. Opt. (1)

Sci. Am. (1)

A. B. Fraser, W. H. Mach, “Mirages,” Sci. Am. 234, 102–111 (1976).
[CrossRef]

Other (3)

“Kodachrome 25, 64, and 200 Professional Film,” Kodak Publication E-55 (Eastman Kodak Company, Rochester, N.Y., 2001). The relevant data sheet is currently available on the Internet at http://www.kodak.com/global/en/professional/support/techPubs/e55/e55.shtml .

W. A. Lyons, “Numerical simulation of Great Lakes conduction inversions,” in Proceedings of the 13th Conference on Great Lakes Research, State University College, Buffalo, N.Y., 1–3April1970, D. V. Anderson, J. S. Seddon, eds. (International Association for Great Lakes Research, Ann Arbor, Mich., 1970), pp. 369–387.

M. Born, E. Wolf, Principles of Optics, 6th ed. (Pergamon, Oxford, UK, 1986), Sec. 4.8.

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Figures (5)

Fig. 1
Fig. 1

Lake Winnipeg, South Basin. The first observation looks past Grand Marais Point toward the far shore, which is 26.4 km from the camera. The second observation looks past Drunken Point to Hecla Island, 28 km away.

Fig. 2
Fig. 2

Bright mirage at Grand Marais Point.

Fig. 3
Fig. 3

Bright mirage at Drunken Point. The noticeable fall-off of brightness with radial distance from the center of the image is due to vignetting. The lens, a Celestron 5-in. telescope attached to a camera with a T adapter, is seriously adversely affected by this flaw. The effect is visible in every photograph made with this lens.

Fig. 4
Fig. 4

Model for the Grand Marais image. (a) Temperature profile used for the first 3 km, where the line of sight is close to the shore; (b) temperature profile over the open lake beyond 3 km; (c) light rays traced backward from the camera. The vertical line at 26.4 km represents the far shore. The elevation angles of the rays span the range [-3′, 7′], at 1′ intervals.

Fig. 5
Fig. 5

Dark mirage at Grand Marais.

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