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Proceedings Paper

Optical attenuation in fog and clouds
Author(s): Robert Michael Pierce; Jaya Ramaprasad; Eric C. Eisenberg
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Paper Abstract

The Kruse formula was originally devised to relate visibility to optical attenuation, from the visible to the near infrared (IR), for dust and small particle aerosols with dimensions much smaller than the wavelength. Application of this formula to attenuation in fog is not appropriate since fogs consist mainly of particles much larger than optical wavelengths. Mie scattering calculations, transmission measurements and simple observations indicate that attenuation from the visible to the near IR is virtually independent of wavelength. The Kruse formula is also shown to be questionable apart form its wavelength dependence; it does not account for scattering into the field of view and does not consider background illumination. In the derivation presented here the visibility is linked to near-forward scattering, not explicitly to attenuation. We conclude that attenuation in fog should be treated as virtually wavelength independent from the visible to the near IR and a more appropriate formula is (Gamma) (V;(lambda) )=(kappa) divided byV(dB/km) where V is the visual range and 8.5dB,(kappa) <17dB.

Paper Details

Date Published: 27 November 2001
PDF: 14 pages
Proc. SPIE 4530, Optical Wireless Communications IV, (27 November 2001); doi: 10.1117/12.449815
Show Author Affiliations
Robert Michael Pierce, Terabeam Corp. (United States)
Jaya Ramaprasad, Terabeam Corp. (United States)
Eric C. Eisenberg, Terabeam Corp. (United States)

Published in SPIE Proceedings Vol. 4530:
Optical Wireless Communications IV
Eric J. Korevaar, Editor(s)

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