Modified Ångström exponent for the characterization of submicrometer aerosols

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https://opg.optica.org/ao/abstract.cfm?uri=ao-40-15-2368

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https://doi.org/10.1364/AO.40.002368
 http://hdl.handle.net/11603/33563

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UMBC GESTAR II
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Author/Creator ORCID

https://orcid.org/0000-0001-9801-1610

Date

2001-05-20

Type of Work

journal articles
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Citation of Original Publication

O’Neill, Norm T., Oleg Dubovik, and Tom F. Eck. “Modified Ångström Exponent for the Characterization of Submicrometer Aerosols.” Applied Optics 40, no. 15 (May 20, 2001): 2368–75. https://doi.org/10.1364/AO.40.002368.

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Subjects

Aerosols
Curvature
Near infrared
Optical computing
Point clouds
Refractive index

Abstract

The classical Ångström exponent is an operationally robust optical parameter that contains size information on all optically active aerosols in the field of view of a sunphotometer. Assuming that the optical effects of a typical (radius) size distribution can be approximated by separate submicrometer and supermicrometer components, we show that one can exploit the spectral curvature information in the measured optical depth to permit a direct estimation of a fine-mode (submicrometer) Ångström exponent (αբ) as well as the optical fraction of fine-mode particles (η). Simple expressions that enable the estimation of these parameters are presented and tested by use of simulations and measurements.