A spectral light absorption meter for measurements in the sea

Højerslev, Niels K.

doi:10.4319/lo.1975.20.6.1024

Cited by 57 publications

(17 citation statements)

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“…The HR-4 was deployed on the seabed with the two hemispherical Gershun sensors positioned 1 m above the bottom measuring downwelling [E g-dn (1)] and upwelling [E g-up (1)] Gershun irradiance (Hojerslev 1975). Total scalar irradiance was calculated as:…”

Section: Apparent Optical Propertiesmentioning

confidence: 99%

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

McPherson

Hill

Zimmerman

et al. 2011

Estuaries and Coasts

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Water column optical properties of Greater Florida Bay were investigated in the context of their impacts on seagrass distribution. Scattering played an important role in light attenuation throughout the shallow water system. The northwest region was characterized by an absence of seagrasses and the highest scattering by particles, mostly from resuspended carbonate sediments. Higher seagrass densities were observed in the open waters just north of the Florida Keys, where absorption coefficients were dominated by colored dissolved organic material and scattering was lower than in the northwest region. Patchy dense seagrass meadows were observed in the clear waters south of the Keys where scattering and absorption were low and contributed equally to light attenuation. In general, seagrasses were observed in areas where >7.5% of surface irradiance reached the plants and where optical properties were not dominated by scattering. Although the prevention of eutrophication and nuisance algal blooms may be necessary for preserving seagrass meadows in this system, our observations and model calculations indicate that nutrient control alone may be insufficient to permit seagrass recolonization if optical properties are dominated by particulate scattering from resuspended sediments.

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Section: Apparent Optical Propertiesmentioning

confidence: 99%

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

McPherson

Hill

Zimmerman

et al. 2011

Estuaries and Coasts

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“…In situ spectral absorption coefficient profiles can be measured with spectral radiometers [7]. This means that in order to calculate the spectral absorption of a particular water layer it is enough to measure a spectra with spectrometer.…”

Section: Dissolved Matters and Chlorophyllmentioning

confidence: 99%

Dissolved Organic Matters Impact on Colour Reconstruction in Underwater Images

et al. 2005

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Abstract. The natural properties of water column usually affect underwater imagery by suppressing high-energy light. In application such as color correction of underwater images estimation of water column parameters is crucial. Diffuse attenuation coefficients are estimated and used for further processing of underwater taken data. The coefficients will give information on how fast light of different wavelengths decreases with increasing depth. Based on the exact depth measurements and data from a spectrometer the calculation of downwelling irradiance will be done. Chlorophyll concentration and a yellow substance factor contribute to a great variety of values of attenuation coefficients at different depth. By taking advantage of variations in depth, a method is presented to estimate the influence of dissolved organic matters and chlorophyll on color correction. Attenuation coefficients that depends on concentration of dissolved organic matters in water gives an indication on how well any spectral band is suited for color correction algorithm.

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“…Unfortunately, only a few direct in situ measurements of a are available (Hojerslev, 1973(Hojerslev, , 1974a(Hojerslev, , 1975(Hojerslev, , 1977a(Hojerslev, , 1978b and the same is partly true for p although more measurements have been made (e.g., Jerlov, 1976). The scattering coefficient b and the attentuation coefficient c are measured more frequently.…”

Section: Color and Optical Properties Of Seawatermentioning

confidence: 99%

Water color and its relation to primary production

Højerslev

1980

Boundary-Layer Meteorol

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It is shown both experimentally and theoretically that the depth of the euphotic zone is related to the color of the sea defined as a color index equal to the ratio of the upwelling blue (450 nm) and green (525 nm) nadir daylight just below the sea surface. The relationship is valid for most sea waters where the albedo from the bottom is negligible near the sea surface and where the composition of suspended and dissolved matter is not largely determined either by water drainage from land or by turbidity currents.The standing stock of phytoplankton and its primary productivity within the euphotic zone can approximately be given in terms of the color of the sea. The accuracy in determining each of the above two biological quantities from color measurements at the sea surface is not satisfactory at present. This holds particularly true when the color of the sea is measured remotely by present satellite techniques.

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A spectral light absorption meter for measurements in the sea

Cited by 57 publications

References 0 publications

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

Dissolved Organic Matters Impact on Colour Reconstruction in Underwater Images

Water color and its relation to primary production

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