Relationships between inherent optical properties and the depth of penetration of solar radiation in optically complex coastal waters

Alexander Cunningham, Leanne Ramage, David McKee

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10 Citations (Scopus)

Abstract

The attenuation of downward planar irradiance can be quantified by KdE10%; , the
diffuse attenuation coefficient calculated from the surface to the depth where the irradiance Ed at wavelength falls to 10% of its surface value. Theoretical studies by Gordon (1989) and Lee et al. (2005a) suggest that Kd E 10%; can be derived from the absorption coefficient, a() and the backscattering coefficient, bb(), using equations incorporating either the solar zenith angle (a) or the subsurface distribution function (D0) and empirical coefficients derived by radiative transfer modeling. These results have not, however, been validated against in situ measurements. We have therefore assessed the performance of both models using measurements of a(), bb(), and Kd E 10%; for 100 stations in UK coastal waters. Best results were obtained from the Lee et al. (2005a) model, for which over 90% of the predicted Kd E 10%; values in the 440 nm to 665 nm range were within 60.1 m1 of those measured in situ. A strong linear relationship (R2> 0.95, mean relative difference 5.4%) was found between Kd E 10% at 490 nm and the reciprocal of the depth of the midpoint of the euphotic zone (z10%, PAR). This allowed (z10%, PAR) to be predicted from measured values of a(490 nm), bb(490 nm) and a, using the Lee et al. model as an intermediate step, with an RMS error of 1.25 m over the 2.5–25.0 m range covered by our data set.
LanguageEnglish
JournalJournal of Geophysical Research: Oceans
Early online date7 May 2013
DOIs
Publication statusPublished - 2013

Fingerprint

coastal water
optical properties
solar radiation
Solar radiation
optical property
penetration
Optical properties
photosynthetically active radiation
irradiance
Water
euphotic zone
absorption coefficient
attenuation coefficients
zenith angle
zenith
coefficients
in situ measurement
theoretical study
radiative transfer
backscattering

Keywords

  • diffuse attenuation models
  • euphotic depth
  • coastal optics

Cite this

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title = "Relationships between inherent optical properties and the depth of penetration of solar radiation in optically complex coastal waters",
abstract = "The attenuation of downward planar irradiance can be quantified by KdE10{\%}; , thediffuse attenuation coefficient calculated from the surface to the depth where the irradiance Ed at wavelength falls to 10{\%} of its surface value. Theoretical studies by Gordon (1989) and Lee et al. (2005a) suggest that Kd E 10{\%}; can be derived from the absorption coefficient, a() and the backscattering coefficient, bb(), using equations incorporating either the solar zenith angle (a) or the subsurface distribution function (D0) and empirical coefficients derived by radiative transfer modeling. These results have not, however, been validated against in situ measurements. We have therefore assessed the performance of both models using measurements of a(), bb(), and Kd E 10{\%}; for 100 stations in UK coastal waters. Best results were obtained from the Lee et al. (2005a) model, for which over 90{\%} of the predicted Kd E 10{\%}; values in the 440 nm to 665 nm range were within 60.1 m1 of those measured in situ. A strong linear relationship (R2> 0.95, mean relative difference 5.4{\%}) was found between Kd E 10{\%} at 490 nm and the reciprocal of the depth of the midpoint of the euphotic zone (z10{\%}, PAR). This allowed (z10{\%}, PAR) to be predicted from measured values of a(490 nm), bb(490 nm) and a, using the Lee et al. model as an intermediate step, with an RMS error of 1.25 m over the 2.5–25.0 m range covered by our data set.",
keywords = "diffuse attenuation models, euphotic depth, coastal optics",
author = "Alexander Cunningham and Leanne Ramage and David McKee",
year = "2013",
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language = "English",
journal = "Journal of Geophysical Research: Oceans",
issn = "0148-0227",

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TY - JOUR

T1 - Relationships between inherent optical properties and the depth of penetration of solar radiation in optically complex coastal waters

AU - Cunningham, Alexander

AU - Ramage, Leanne

AU - McKee, David

PY - 2013

Y1 - 2013

N2 - The attenuation of downward planar irradiance can be quantified by KdE10%; , thediffuse attenuation coefficient calculated from the surface to the depth where the irradiance Ed at wavelength falls to 10% of its surface value. Theoretical studies by Gordon (1989) and Lee et al. (2005a) suggest that Kd E 10%; can be derived from the absorption coefficient, a() and the backscattering coefficient, bb(), using equations incorporating either the solar zenith angle (a) or the subsurface distribution function (D0) and empirical coefficients derived by radiative transfer modeling. These results have not, however, been validated against in situ measurements. We have therefore assessed the performance of both models using measurements of a(), bb(), and Kd E 10%; for 100 stations in UK coastal waters. Best results were obtained from the Lee et al. (2005a) model, for which over 90% of the predicted Kd E 10%; values in the 440 nm to 665 nm range were within 60.1 m1 of those measured in situ. A strong linear relationship (R2> 0.95, mean relative difference 5.4%) was found between Kd E 10% at 490 nm and the reciprocal of the depth of the midpoint of the euphotic zone (z10%, PAR). This allowed (z10%, PAR) to be predicted from measured values of a(490 nm), bb(490 nm) and a, using the Lee et al. model as an intermediate step, with an RMS error of 1.25 m over the 2.5–25.0 m range covered by our data set.

AB - The attenuation of downward planar irradiance can be quantified by KdE10%; , thediffuse attenuation coefficient calculated from the surface to the depth where the irradiance Ed at wavelength falls to 10% of its surface value. Theoretical studies by Gordon (1989) and Lee et al. (2005a) suggest that Kd E 10%; can be derived from the absorption coefficient, a() and the backscattering coefficient, bb(), using equations incorporating either the solar zenith angle (a) or the subsurface distribution function (D0) and empirical coefficients derived by radiative transfer modeling. These results have not, however, been validated against in situ measurements. We have therefore assessed the performance of both models using measurements of a(), bb(), and Kd E 10%; for 100 stations in UK coastal waters. Best results were obtained from the Lee et al. (2005a) model, for which over 90% of the predicted Kd E 10%; values in the 440 nm to 665 nm range were within 60.1 m1 of those measured in situ. A strong linear relationship (R2> 0.95, mean relative difference 5.4%) was found between Kd E 10% at 490 nm and the reciprocal of the depth of the midpoint of the euphotic zone (z10%, PAR). This allowed (z10%, PAR) to be predicted from measured values of a(490 nm), bb(490 nm) and a, using the Lee et al. model as an intermediate step, with an RMS error of 1.25 m over the 2.5–25.0 m range covered by our data set.

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