Detailed validation of the bidirectional effect in various Case 1 waters for application to ocean color imagery

Voss, Kenneth J.; Morel, A.; Antoine, David

doi:10.5194/bg-4-781-2007

Cited by 41 publications

(28 citation statements)

References 16 publications

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“…Several models have been put forward for the variation in the upwelling radiance field and the effect of this variation on interpretation of measurements of the ocean reflectance made above the water [e.g., Mobley , 1989; Morel and Gentili , 1993; Voss et al , 2007; Zaneveld et al , 2001a, 2001b]. For example, the often used “ Q ” factor, the ratio of upwelling irradiance to upwelling nadir radiance, has been shown to be much more variable than previously thought [ Hirata et al , 2009; Morel et al , 2002; Zibordi and Berthon , 2001].…”

Section: Introductionmentioning

confidence: 99%

Quantitative estimation of the underwater radiance distribution

Lewis

Wei

Dommelen³

et al. 2011

J. Geophys. Res.

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[1] Within the Radiance in a Dynamic Ocean (RaDyO) program, we have created and deployed a high dynamic range camera that can resolve the full spherical radiance distribution at the ocean surface and at depth. We present here the first results from deployments of the camera in near-surface water in eutrophic, mesotropic, and oligotropic environments. The instrument resolves the dynamics and fine structure of both the downwelling and upwelling radiance distribution and its variation with depth in these optically diverse water types. The various irradiances (E d , E u , E o , E ou , and E od ) are computed by integration. The distribution functions (e.g., the average cosines) are computed directly, as are the various diffuse attenuation coefficients. The fully specified radiance field therefore provides all the pertinent information to derive not only all of the apparent optical properties but, in principle, the inherent optical properties such as the absorption coefficient and the phase function as well. Comparison of the measured radiance field to independent measurements has shown very good agreement.

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Section: Introductionmentioning

confidence: 99%

Quantitative estimation of the underwater radiance distribution

Lewis

Wei

Dommelen³

et al. 2011

J. Geophys. Res.

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“…The bidirectional function Q has values between 3.5 and 5 sr depending on many variables, including inherent optical properties of the water, wavelength, and solar zenith angles Voss et al, 2007). For simplicity here we assume that Q = 4 sr. Model R RS is therefore analogous but not exactly the same as that measured by satellite.…”

Section: Surface Reflectancementioning

confidence: 99%

Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

et al. 2015

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Abstract. We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high-latitude productivity. This new model that captures biooptical feedbacks will be important for improving our understanding of the role of light and optical constituents on ocean biogeochemistry, especially in a changing environment. Further, resolving surface upwelling irradiance will make it easier to connect to satellite-derived products in the future.

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“…The Fresnel's reflection on the agitated sea surface is taken into account using the Cox and Munk model (Cox and Munk, 1954). The water leaving radiance is nearly isotropic (Voss et al, 2007) and modeling shows that its polarization is negligible (e.g. Chami et al, 2001;Chowdhary et al, 2006;Ota et al, 2010).…”

Section: Modeling Surface Reflectancementioning

confidence: 99%

Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations

et al. 2011

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Abstract. The proposed development is an attempt to enhance aerosol retrieval by emphasizing statistical optimization in inversion of advanced satellite observations. This optimization concept improves retrieval accuracy relying on the knowledge of measurement error distribution. Efficient application of such optimization requires pronounced data redundancy (excess of the measurements number over number of unknowns) that is not common in satellite observations. The POLDER imager on board the PARASOL microsatellite registers spectral polarimetric characteristics of the reflected atmospheric radiation at up to 16 viewing directions over each observed pixel. The completeness of such observations is notably higher than for most currently operating passive satellite aerosol sensors. This provides an opportunity for profound utilization of statistical optimization principles in satellite data inversion. The proposed retrieval scheme is designed as statistically optimized multi-variable fitting of all available angular observations obtained by the POLDER sensor in the window spectral channels where absorption by gas is minimal. The total number of such observations by PARASOL always exceeds a hundred over each pixel and the statistical optimization concept promises to be efficient even if the algorithm retrieves several tens of aerosol parameters. Based on this idea, the proposed algorithm uses a large number of unknowns and is aimed at retrieval of extended set of parameters affecting measured radiation.Correspondence to: O. Dubovik (dubovik@loa.univ-lille1.fr)The algorithm is designed to retrieve complete aerosol properties globally. Over land, the algorithm retrieves the parameters of underlying surface simultaneously with aerosol. In all situations, the approach is anticipated to achieve a robust retrieval of complete aerosol properties including information about aerosol particle sizes, shape, absorption and composition (refractive index). In order to achieve reliable retrieval from PARASOL observations even over very reflective desert surfaces, the algorithm was designed as simultaneous inversion of a large group of pixels within one or several images. Such multi-pixel retrieval regime takes advantage of known limitations on spatial and temporal variability in both aerosol and surface properties. Specifically the variations of the retrieved parameters horizontally from pixel-to-pixel and/or temporary from day-to-day are enforced to be smooth by additional a priori constraints. This concept is expected to provide satellite retrieval of higher consistency, because the retrieval over each single pixel will be benefiting from coincident aerosol information from neighboring pixels, as well, from the information about surface reflectance (over land) obtained in preceding and consequent observations over the same pixel.The paper provides in depth description of the proposed inversion concept, illustrates the algorithm performance by a series of numerical tests and presents the examples of preliminary retrieval results o...

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Detailed validation of the bidirectional effect in various Case 1 waters for application to ocean color imagery

Cited by 41 publications

References 16 publications

Quantitative estimation of the underwater radiance distribution

Quantitative estimation of the underwater radiance distribution

Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations

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