An opaque cloud cover model of sky short wavelength radiance

Harrison, A. W.; Coombes, Charles A.

doi:10.1016/0038-092x(88)90035-7

Cited by 86 publications

(40 citation statements)

References 12 publications

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“…For each distribution, the sky and sea were considered to be cloudless and calm, respectively. The sky irradiance was calculated using the Radtran model (Gregg and Carder 1990), and the sky radiance distribution was calculated using the model given in Harrison and Coombes (1988). Pure water absorption was taken from Pope and Fry (1997).…”

Section: Calculation Of Underwater Radiances and Irradiances-mentioning

confidence: 99%

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

Johnsen

Sosik

2003

Limnology & Oceanography

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Mirrored and colored surfaces are common adaptations for crypsis in pelagic habitats. Although highly successful when optimized for a particular situation, either may become less successful if it is then viewed in a different situation. In this study we examine the relative robustness of these two strategies by determining how visible an organism becomes when viewed under optical conditions different from those under which the camouflage is optimal. Underwater radiance distributions were calculated using inherent optical properties measured in coastal waters 80 km off the coast of New Hampshire. These radiance distributions were then used to calculate optimally cryptic diffuse and specular reflectance spectra as a function of depth, solar elevation, viewing angle, and azimuth. Then the visibilities of organisms cryptic in one situation viewed in a different situation were calculated, using the Atlantic Cod, Gadus morhua, as the viewer. In contrast to benthic organisms, pelagic organisms cryptic under one set of optical conditions were quite visible under a different set, particularly when viewed from a different azimuth. The crypsis afforded by mirrored surfaces was generally more robust than that resulting from colored surfaces. However, because mirrored surfaces could never be perfectly cryptic when viewed in the azimuth of the sun, neither strategy clearly outperformed the other. In general, crypsis by colored or mirrored surfaces was not robust in nearsurface water, which may help explain both the predominance of transparent species in near-surface pelagic habitats and the vertical migration of many colored and mirrored species. The results also show that three common foraging strategies-circling, crepuscular activity, and driving prey toward the surface-all increase the visibility of cryptically colored or mirrored prey.

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Section: Calculation Of Underwater Radiances and Irradiances-mentioning

confidence: 99%

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

Johnsen

Sosik

2003

Limnology & Oceanography

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“…Except where specifically noted, the spectral distribution of irradiance incident on the sea surface and the angular distribution of incident radiance are modeled realistically (Gregg and Carder 1990;Kasten and Czeplak 1980;Harrison and Coombes 1988). The sun is placed at 45" from the zenith and the sky was 70% overcast.…”

Section: Approachmentioning

confidence: 99%

Effect of Raman scattering on the average cosine and diffuse attenuation coefficient of irradiance in the ocean

Berwald

Stramski

Mobley

et al. 1998

Limnology & Oceanography

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We have investigated the effect of Raman scattering on the average cosine of underwater irradiance, ,%, the diffuse attenuation coefficient of irradiance, K, and the Raman scattering source coefficient, P*, throughout the water column and into the asymptotic field. The Raman scattering source coefficient is the fractional gain in the scalar irradiance from local Raman scattering at a given depth, and it can be found from the Gershun equation with a Raman source term. In particular, by using calculations from a radiative transfer model (Hydrolight 3.0), we compare ,%, K, and P* from simulations that include and that omit Raman scattering. These simulations are performed at wavelengths between 355 and 665 nm in a vertically homogeneous ocean with inherent optical properties (IOPs) determined from case 1 bio-optical models for three different chlorophyll concentrations (0.05, 0.5, and 5 mg m-j). We also investigated several two-layered oceans that assumed different inherent optical properties in the surface and deep layers. Our calculations showed that when Raman scattering is present, there may exist strong vertical gradients in the average cosine and the diffuse attenuation coefficient, especially at long wavelengths for low chlorophyll concentrations. In addition, a quasi-asymptotic field may be a feature of the vertical profiles of the average cosine and the diffuse attenuation coefficient. In the asymptotic field, there is no effect of Raman scattering at shorter wavelengths, there is a strong effect of Raman scattering at longer wavelengths and between these two spectral regions, and there is a transition that increases from 500 to 590 nm as the concentration of chlorophyll increases from 0.05 to 5 mg m-2. Over a broad range of IOPs, the asymptotic parameters pm*, K,*, and P*, are related by a quadratic relationship. Neither the magnitude or angular distribution of surface light nor changes in the absorption and scattering coefficients in the surface layer of a two-layered ocean have auy effect on the values of ,%=*, K,*, and P*,; the values of these parameters depend only upon the IOPs in the deepest layer.

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“…Phase functions for pure seawater and particles are were taken from Morel [1974] and Petzold [1972]. Atmospheric radiance distribution was calculated from Harrison and Coombes [1988] and Gregg and Carder [1990] for solar angle q s from 0 to 70 degrees. Wind roughened surface [Cox and Munk, 1954] was considered with a wind speed of 7.2 m s The average cosine of pure seawater, particle and total VSF at backscattering angles k Imaginary part of (complex) effective refractive index of particles …”

Section: Appendix Bmentioning

confidence: 99%

Relationship between the irradiance reflectance and inherent optical properties of seawater

Hirata

Højerslev

2008

J. Geophys. Res.

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[1] A new expression for relationship between the surface irradiance reflectance and Inherent Optical Properties (IOPs) of homogeneous seawater is presented. Physical parameters largely responsible for the relationship are identified. These are the average cosines of the backward volume scattering function and of the downward radiance. Lorenz-Mie computations show that the average cosine of the backward volume scattering function is quasi-constant (0.493 ± 0.135) for most marine waters, even if the backward volume scattering function itself is considerably variable. As a result, a base magnitude of the proportionality between the irradiance reflectance and IOPs are largely set by the average cosine of the backward volume scattering function and eventually determined by the average cosine of the downward radiance that is primarily driven by the sun angle. Independent numerical simulations of radiative transfer support results of the new expression to show that it gives significant improvement in both physical understanding and numerical prediction of the relationship.Citation: Hirata, T., and N. K. Højerslev (2008), Relationship between the irradiance reflectance and inherent optical properties of seawater,

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An opaque cloud cover model of sky short wavelength radiance

Cited by 86 publications

References 12 publications

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

Effect of Raman scattering on the average cosine and diffuse attenuation coefficient of irradiance in the ocean

Relationship between the irradiance reflectance and inherent optical properties of seawater

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