Monte Carlo and discrete-ordinate simulations of irradiances in the coupled atmosphere-ocean system

Gjerstad, Karl Idar; Stamnes, Jakob J.; Hamre, Børge; Lotsberg, Jon Kåre; Yan, Banghua; Stamnes, Knut

doi:10.1364/ao.42.002609

Cited by 76 publications

(27 citation statements)

References 25 publications

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“…In addition to affecting reflection, the surface roughness itself significantly affects the directional character of the beam transmitted beneath the air-water interface. Gjerstal and co-workers 9 proposed an ad hoc method to consider the surface roughness in the discrete-ordinate method. They mimic the irradiances from a Monte Carlo model by adjusting the refractive index in…”

Section: Introductionmentioning

confidence: 99%

Analytical solution of radiative transfer in the coupled atmosphere-ocean system with a rough surface

et al. 2006

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Using the efficient discrete-ordinate method, we present an analytical solution for radiative transfer in the coupled atmosphere-ocean system with rough air-water interface.The theoretical formulations of the radiative transfer equation and solution are described.The effects of surface roughness on radiation field in the atmosphere and ocean are studied and compared with measurements. The results show that ocean surface roughness has significant effects on the upwelling radiation in the atmosphere and the downwelling radiation in the ocean. As wind speed increases, the angular domain of sunglint broadens, the surface albedo decreases, and the transmission to ocean increases. The downward radiance field in the upper ocean is highly anisotropic, but this anisotropy decreases rapidly as surface wind increases and as depth in ocean increases. The effects of surface roughness on radiation also depend greatly on both wavelength and angle of incidence (i.e., solar elevation); these effects are significantly smaller throughout the spectrum at high sun. The model-observation discrepancies may indicate that the Cox-Munk surface roughness model is not sufficient for high wind conditions.

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Section: Introductionmentioning

confidence: 99%

Analytical solution of radiative transfer in the coupled atmosphere-ocean system with a rough surface

et al. 2006

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“…A detailed description of the CAO-DISORT model is available in Jin & Stamnes (1994) and Hamre et al (2004). The CAO-DISORT model has been extensively tested both against other deterministic radiative transfer codes as well as against stochastic Monte Carlo codes (Mobley et al 1993, Gjerstad et al 2003.Primary production. Calculations of photosynthetic rates were based upon measurements of natural fluorescence, modelling based on measured PAR and UVR 82 Erga et al: UV transmission in Norwegian marine waters and 14 C-uptake.…”

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confidence: 99%

UV transmission in Norwegian marine waters: controlling factors and possible effects on primary production and vertical distribution of phytoplankton

Erga¹,

Aursland²,

Frette³

et al. 2005

Mar. Ecol. Prog. Ser.

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We investigated the ultraviolet radiation (UVR) transmission properties of Norwegian oceanic, coastal and fjord waters, and how they influence the primary production and vertical distribution of phytoplankton. Values of the 1% UVR attenuation depth and diffuse attenuation coefficients (K d ) in the Greenland and Norwegian Seas (GNS), in the coastal waters of south-western Norway (SWN) and in the Samnanger fjord (SAF) are presented. Maximum penetration of UVR in the GNS was confirmed by K d (320) = 0.25 m -1 , and mimimum penetration in the SAF, by K d (320) = 9 m -1 . In the GNS, K d and chlorophyll a (chl a) were closely correlated, while coloured dissolved organic matter (CDOM) was the main contributor to ultraviolet (UV) attenuation in the SAF. Also, in SWN waters, CDOM was more important than chl a for UV attenuation, but less important than in SAF waters. In GNS and SAF waters the average vertical distribution of chl a had its maximum in the upper 10 and 7.5 m of the water column, respectively, while in SWN waters it had its maximum at 20 m. The depths with the highest photosynthetic rates per unit volume decreased successively from the oceanic waters of the GNS via the coastal waters of the SWN to the fjord waters of the SAF. Under similar PAR intensities, however, the water column photosynthetic efficiency (integrated carbon assimilation/chl a ratio) was highest in SWN waters. Maximum and mean percentage potential for inhibition of the estimated (from PAR and UV) primary production due to UVR at a depth of 5 m were 11 and 4.3% in the GNS, 3.2 and 0.9% in the SWN and 0.5 and 0.1% in the SAF. The UVR potential for inhibition was significant down to a depth of 10 m in the GNS, down to a depth of 5 m in the waters of the SWN, while it was seldom found deeper than 3 m in the SAF. These variations could be ascribed to differences in CDOM concentrations and mixed-layer depths. The optical properties of the investigated water masses were found to be highly influenced by the circulation patterns. KEY WORDS: UV transmission · Norwegian waters · Phytoplankton · Primary production Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 305: 2005 total ozone has been observed at middle and high latitudes in the Northern Hemisphere during the last decades (Stolarski et al. 1992, Jokela et al. 1993, Varotsos et al. 1998, Dahlback 2002. According to Austin et al. (1992), Bjørn et al. (1998) and Hessen (2002), this tendency is expected to continue in the 21st century. In addition, there is a tendency towards more rapid depletion of the ozone layer over Scandinavia than over most other geographical regions at corresponding latitudes. In contrast to the antarctic ozone hole, which occurs regularly both on a spatial and a temporal scale (Hofmann et al. 1992, Davidson & van der Heijden 2000, the arctic ozone hole seems to occur irregularly (Stamnes et al. 1988, Jokela et al. 1993). The radiation levels within both the visible and the UV bands decrease with increasing la...

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“…The propagation of light through the sea surface is calculated from the reflected and transmitted angles using the Fresnel function (Gjerstad et al, 2003). Since the resulting underwater light fields strongly depend on the exact shape of the wave, the slope of the sea surface plays an important role in determining the transmitted and reflected angles.…”

Section: Surface Transmittancementioning

confidence: 99%

Modelling of underwater light fields in turbid and eutrophic waters: application and validation with experimental data

Sundarabalan

Shanmugam

2015

Ocean Sci.

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Abstract.A reliable radiative transfer (RT) model is an essential and indispensable tool for understanding the radiative transfer processes in homogenous and layered waters, analyzing measurements made by radiance sensors and developing remote-sensing algorithms to derive meaningful physical quantities and biogeochemical variables in turbid and productive coastal waters. Existing radiative transfer models have been designed to be applicable to either homogenous waters or inhomogeneous waters. To overcome such constraints associated with these models, this study presents a radiative transfer model that treats a homogenous layer as a diffuse part and an inhomogeneous layer as a direct part in the water column and combines these two parts appropriately in order to generate more reliable underwater lightfield data such as upwelling radiance (L u ), downwelling irradiance (E d ) and upwelling irradiance (E u ). The diffuse model assumes the inherent optical properties (IOPs) to be vertically continuous and the light fields to exponentially decrease with depth, whereas the direct part considers the water column to be vertically inhomogeneous (layer-by-layer phenomena) with the vertically varying phase function. The surface and bottom boundary conditions, source function due to chlorophyll and solar incident geometry are also included in the present RT model. The performance of this model is assessed in a variety of waters (clear, turbid and eutrophic) using the measured radiometric data. The present model shows an advantage in terms of producing accurate L u , E d and E u profiles (in spatial domain) in different waters determined by both homogenous and inhomogeneous conditions. The feasibility of predicting these underwater light fields based on the remotely estimated IOP data is also examined using the present RT model. For this application, vertical profiles of the water constituents and IOPs are estimated by empirical models based on our in situ data. The present RT model generates L u , E d and E u spectra closely consistent with the measured data. These results lead to a conclusion that the present RT model is a viable alternative to existing RT models and has an important implication for remote sensing of optically complex waters.

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Monte Carlo and discrete-ordinate simulations of irradiances in the coupled atmosphere-ocean system

Cited by 76 publications

References 25 publications

Analytical solution of radiative transfer in the coupled atmosphere-ocean system with a rough surface

Analytical solution of radiative transfer in the coupled atmosphere-ocean system with a rough surface

UV transmission in Norwegian marine waters: controlling factors and possible effects on primary production and vertical distribution of phytoplankton

Modelling of underwater light fields in turbid and eutrophic waters: application and validation with experimental data

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