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Determination of the Optical Thickness and Effective Particle Radius of Clouds from Reflected Solar Radiation Measurements. Part 1: Theory
Nakajima, Teruyuki
3348
King, Michael D.
3349
451
A method is presented for determining the optical thickness and effective particle radius of stratiform cloud layers from reflected solar radiation measurements. A detailed study is presented which shows that the cloud optical thickness (τc) and effective particle radius (re) of water clouds can be determined solely from reflection function measurements at 0.75 and 2.16 μm, provided τc ≳ 4 and re ≳ 6 μm. For optically thin clouds the retrieval becomes ambiguous, resulting in two possible solutions for the effective radius and optical thickness. Adding a third channel near 1.65 μm does not improve the situation noticeably, whereas the addition of a channel near 3.70 μm reduces the ambiguity in deriving the effective radius. The effective radius determined by the above procedure corresponds to the droplet radius at some optical depth within the cloud layer. For clouds having τc ≳ 8, the effective radius determined using the 0.75 and 2.16 μm channels can be regarded as 85%-95% of the radius at cloud top, which corresponds in turn to an optical depth 20%-40% of the total optical thickness of the cloud layer.
journal article
American Meteorological Society
1990-08-01
application/pdf
Journal of the atmospheric sciences
15
47
1878
1893
AA00693875
00224928
https://repository.dl.itc.u-tokyo.ac.jp/record/868/files/Nakajima1990JAS_H24P20.pdf
eng
info:doi/10.1175/1520-0469(1990)047<1878:DOTOTA>2.0.CO;2
http://doi.org/10.1175/1520-0469(1990)047<1878:DOTOTA>2.0.CO;2
© Copyright 1990 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyright@ametsoc.org.