- The propagation of downwelling irradiance at wavelength l from surface to a depth
(z) in the ocean is governed by the diffuse attenuation coefficient, K𝒹(λ). There are two
standard methods for the derivation of K𝒹(λ) in remote sensing, which both are based on
empirical relationships involving the blue-to-green ratio of ocean color. Recently, a
semianalytical method to derive K𝒹(λ) from reflectance has also been developed. In this
study, using K𝒹(490) and K𝒹(443) as examples, we compare the K𝒹(λ) values derived from
the three methods using data collected in three different regions that cover oceanic and
coastal waters, with K𝒹(490) ranging from ~0.04 to 4.0 m⁻¹. The derived values are
compared with the data calculated from in situ measurements of the vertical profiles of
downwelling irradiance. The comparisons show that the two standard methods produced
satisfactory estimates of K𝒹(λ) in oceanic waters where attenuation is relatively low but
resulted in significant errors in coastal waters. The newly developed semianalytical
method appears to have no such limitation as it performed well for both oceanic and
coastal waters. For all data in this study the average of absolute percentage difference
between the in situ measured and the semianalytically derived K𝒹 is ~14% for λ = 490 nm
and ~11% for λ = 443 nm.
- Lee, Z.-P., M. Darecki, K. L. Carder, C. O. Davis, D. Stramski, and W. J. Rhea (2005), Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods, Journal of Geophysical Research, 110, C02017, doi:10.1029/2004JC002573.
|Funding Statement (additional comments about funding)
- Support for this study was provided by theNaval Research Laboratory’s basic research P.E. 06010115N ‘‘HyperspectralCharacterization of the Coastal Zone’’ (NRL), the Polish NationalCommittee for Scientific Research Grant PBZ-KBN 056/P04/2001 (M.D.),ONR contract N00014-02-1-0211 (K.L.C.), and NASA grants NAGW10288(NRL), NAS5-31716 (K.L.C.), and NAG5-12397 (D.S.).
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