A comparison of methods for the measurement of the absorption coefficient in natural waters

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Read Full Article Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. C7, PAGES 13,201–13,220, 1995 A comparison of methods for the measurement of the absorption coefficient in natural waters W. Scott Pegau College of Atmospheric and Oceanic Science, Oregon State University, Corvallis Joan S. Cleveland Center for Hydro-Optics and Remote Sensing, San Diego State University, San Diego, California W. Doss Tetra Tech Data Systems, Incorporated, Carlsbad, California C. Dan Kennedy Naval Research Laboratory, Stennis Space Center, Mississippi Robert A. Maffione SRI International, Menlo Park, California James L. Mueller Center for Hydro-Optics and Remote Sensing, San Diego State University, San Diego, California R. Stone Tetra Tech Data Systems, Incorporated, Carlsbad, California Charles C. Trees Center for Hydro-Optics and Remote Sensing, San Diego State University, San Diego, California Alan D. Weidemann Naval Research Laboratory, Stennis Space Center, Mississippi Willard H. Wells Tetra Tech Data Systems, Incorporated, Carlsbad, California J. Ronald V. Zaneveld College of Atmospheric and Oceanic Science, Oregon State University, Corvallis Abstract In the spring of 1992 an optical closure experiment was conducted at Lake Pend Oreille, Idaho. A primary objective of the experiment was to compare techniques for the measurement of the spectral absorption coefficient and other inherent optical properties of natural waters. Daily averages of absorption coefficients measured using six methods are compared at wavelengths of 456, 488, and 532 nm. Overall agreement was within 40% at 456 nm and improved with increasing wavelength to 25% at 532 nm. These absorption measurements were distributed over the final 9 days of the experiment, when bio-optical conditions in Lake Pend Oreille (as indexed by the beam attenuation coefficient c_p (660) and chlorophyll a fluorescence profiles) were representative of those observed throughout the experiment. However, profiles of stimulated chlorophyll a fluorescence and beam transmission showed that bio-optical properties in the lake varied strongly on all time and space scales. Therefore environmental variability contributed significantly to deviations between daily mean absorption coefficients measured using the different techniques. Received 25 April 1994; accepted 22 December 1994. Read Full Article Cited by Citation: Pegau, W. S., et al. (1995), A comparison of methods for the measurement of the absorption coefficient in natural waters, J. Geophys. Res., 100(C7), 13,201–13,220. Copyright 1995 by the American Geophysical Union.

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