Optical thickness

From Glossary of Meteorology
Revision as of 15:47, 20 February 2012 by imported>Perlwikibot
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

optical thickness

  1. (Also absorption optical thickness, scattering optical thickness, total optical thickness, optical depth.) The (dimensionless) line integral of the absorption coefficient, or of the scattering coefficient, or of the sum of the two, along any path in a scattering and absorbing medium.

    More often than not, the qualifiers "absorption," "scattering," and "total" are omitted (context sometimes being sufficient to determine which is meant). Optical thickness also depends on the wavelength of the radiation of interest. In a uniform medium, optical thickness has a simple physical interpretation as the length of a path in units of mean free path. Optical thickness and optical depth are used more or less synonymously; if there is a distinction between them it is that optical thickness is applied to an entire path through a medium. Normal optical thickness is optical thickness along a vertical path.
    Compare optical pathlength.

  2. The degree to which a cloud modifies the light passing through it.

    Optical thickness depends on the physical constitution (crystals, drops, droplets), and the form; the overall effect depends on the scatter parameter and the phase function for the particles as well as their concentration and the vertical extent of the cloud.

Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.