Verification of a Linear Relation between IR Extinction, Absorption and Liquid Water Content of Fogs

R. G. Pinnick U.S. Army Atmospheric Sciences Laboratory, While Sands Missile Range, NM 88002

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S. G. Jennings Department of Pure and Applied Physics, University of Manchester Institute of Science and Technology, Manchester, England

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Petr Chýlek Center for Earth and Planetary Physics, Harvard University, Cambridge, MA 02138

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H. J. Auvermann Physical Sciences Laboratory, New Mexico State University, Las Cruces, NM 88003

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Abstract

A linear relationship, independent of the form of the size-distribution, between extinction at wave-lengths around λ = 11 µm, absorption around λ = 3.8 and 9.5 µm, and liquid water content of atmospheric fogs has been verified using 341 droplet size distribution measurements made under a variety of meteorological conditions. The results suggest that integrated liquid water content along a path in fog can be determined from measurement of CO2 laser (λ = 10.6 µm) transmission along the path, and that liquid water content at a particular point in fog can be inferred from in situ measurement of fog-droplet absorption with a deuterium fluoride laser (λ = 3.8 µm) or a suitably tuned C02 laser (λ = 9.5 µm) spectrophone.

Abstract

A linear relationship, independent of the form of the size-distribution, between extinction at wave-lengths around λ = 11 µm, absorption around λ = 3.8 and 9.5 µm, and liquid water content of atmospheric fogs has been verified using 341 droplet size distribution measurements made under a variety of meteorological conditions. The results suggest that integrated liquid water content along a path in fog can be determined from measurement of CO2 laser (λ = 10.6 µm) transmission along the path, and that liquid water content at a particular point in fog can be inferred from in situ measurement of fog-droplet absorption with a deuterium fluoride laser (λ = 3.8 µm) or a suitably tuned C02 laser (λ = 9.5 µm) spectrophone.

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