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Estimates of Radiance Reflected Towards the Zenith at the Surface of the Sea : Volume 6, Issue 4 (05/10/2010)

By Aas, E.

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Book Id: WPLBN0004020483
Format Type: PDF Article :
File Size: Pages 16
Reproduction Date: 2015

Title: Estimates of Radiance Reflected Towards the Zenith at the Surface of the Sea : Volume 6, Issue 4 (05/10/2010)  
Author: Aas, E.
Volume: Vol. 6, Issue 4
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2010
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Aas, E. (2010). Estimates of Radiance Reflected Towards the Zenith at the Surface of the Sea : Volume 6, Issue 4 (05/10/2010). Retrieved from http://worldlibrary.net/


Description
Description: Department of Geosciences, University of Oslo, Norway. Remote sensing of water colour by ship-mounted sensors represents an important tool for the validation of satellite products and the monitoring of water quality. The recorded radiance from the sea has to be corrected for the surface-reflected radiance from sun and sky in order to obtain the water-leaving radiance. Here the simple case of radiance reflected towards the zenith is studied. A set of observed sky radiance and solar irradiance data from Oslo has been used together with a Gaussian slope distribution for the sea surface in order to estimate the reflected radiance. The spectral range studied is 405–650 nm, the solar zenith angles are in the range 37°–76°, and the wind speeds are up to 10 m s−1. The analysis of the results show that the reflected radiance has to be separated into three contributions: sky radiance and sun rays reflected at the foam-free surface and irradiance reflected by whitecaps and foam. It is then demonstrated that by using four input values, namely the downward irradiance, the sky radiance from the zenith, the solar zenith angle and the wind speed, it is possible to obtain by simple expressions estimates of the reflected radiance that only differ from the former calculated values by relative errors of less than 5%. The analysis also indicates that for the spectral range studied neither the water-leaving radiance nor the surface-reflected radiance can be disregarded relative to the other one in the Case 2 waters of the Oslofjord-Skagerrak area. The results form a first step towards the study of reflected radiance in viewing angles differing from the nadir direction.

Summary
Estimates of radiance reflected towards the zenith at the surface of the sea

Excerpt
Aas, E.: Calibration of a marine radiance and colour index meter, Rep. No. 87, Dept. Geophys., Univ. Oslo, 1993.; Aas, E. and Høkedal, J.: Reflection of spectral sky irradiance on the surface of the sea and related properties, Remote Sens. Environ., 70, 181–190, 1999.; Aas, E. and Højerslev, N. K.: Analysis of underwater radiance observations: Apparent optical properties and analytic functions describing the angular radiance distribution, J. Geophys. Res., 104, 8015–8024, 1999.; Aas, E., Højerslev, N. K. and Høkedal, J.: Conversion of sub-surface reflectances to above-surface MERIS reflectance, Int. J. Remote Sens., 30, 5767–5791, 2009.; Aas, E. and Korsbø, B.: Self-shading effect by radiance meters on upward radiance observed in coastal waters, Limn. Oceanogr., 42, 968–974, 1997.; Abramowitz, M. and Stegun, I. A.: Handbook of Mathematical Functions, Dover Publ., New York, 1970.; Aas, E., Højerslev, N. K. and Lundgren, B.: Spectral irradiance, radiance and polarization data from the Nordic Cruise in the Mediterranean Sea during June-July 1971, Rep. No. 102, Dept. Geophys., Univ. Oslo, Norway, 1997.; Adams, J. T., Aas, E., Højerslev, N. K., and Lundgren, B.: Comparison of radiance and polarization values observed in the Mediterranean Sea and simulated in a Monte Carlo model, Appl. Opt., 41, 2724–2733, 2002.; Austin, R. W.: The remote sensing of spectral radiance from below the ocean surface, edited by: Jerlov, N. G. and Steeman Nielsen, E.: Optical Aspects of Oceanography, Academic Press, London, 317–344, 1974.; Cox, C. and Munk, W.: Statistics of the sea surface derived from sun glitter, J. Mar. Res., 13, 198–227, 1954a.; Cox, C. and Munk, W.: The measurements of the roughness of the sea surface from photographs of the sun's glitter, J. Opt. Soc. Am., 44, 838–850, 1954b.; Deschamps, P.-Y., Fougnie, B., Frouin, R., Lecomte, P., and Verwaerde, C.: SIMBAD: a field radiometer for satellite ocean-color validation, Appl. Opt., 43, 4055–4069, 2004.; Fougnie, B., Frouin, R., Lecomte, P., and Deschamps, P.-Y.: Reduction of skylight reflection effects in the above-water measurement of diffuse marine reflectance, Appl. Opt., 38, 3844–3856, 1999.; Frouin, R., Schwindling, M., and Deschamps, P.-Y.: Spectral reflectance of sea foam in the visible and near-infrared: In situ measurements and remote sensing implications, J. Geophys. Res., 101, 14361–14371, 1996.; Gordon, H. R. and Ding, K.: Self-shading of in-water optical instruments, Limn. Oceanogr., 37, 491–500, 1992.; Monohan, E. C.: Oceanic whitecaps, J. Phys. Oceanogr., 1, 139–144, 1971.; Gordon, H. R. and Wang, M.: Surface-roughness considerations for atmospheric correction of ocean color sensors I: The Rayleigh-scattering component, Appl. Opt., 31, 4247–4260, 1992a.; Gordon, H. R. and Wang, M.: Surface-roughness considerations for atmospheric correction of ocean color sensors II: Error in the retrieved water-leaving radiance, Appl. Opt., 31, 4261–4267, 1992b.; Hooker, S. B., Lazin, G., Zibordi, G., and McLean, S.: An evaluation of above- and in-water methods for determining water-leaving radiances, J. Atmos. Oceanic Techn., 19, 486–515, 2002.; Højerslev, N. K. and Aas, E.: Spectral irradiance, radiance and polarization in blue Western Mediterranean waters, in Ocean Optics XIII, Proc., 22-25 October 1996, Halifax, Canada, SPIE Vol. 2963, 138–147, 1997.; Høkedal, J. and Aas, E.: Observations of spectral sky radiance and solar irradiance, Rep. No. 103, Dept. Geophys., Univ. Oslo, Norway, 1998.; Kattawar, G. W. and Adams, C. N.: Errors in radiance calculations induced by using scalar rather than Stokes vector theory in a realistic atmosphere-ocean system, in Ocean Optics X, Proc., 16-18 April 1990, Orlando, Florida, SPIE Vol. 1302, 2–12, 1990.; Koepke, P.: Effective reflectance of oceanic whitecaps, Appl. Opt., 23, 1816–1824, 1984.; Kokhanovsky, A. A.: Spectral reflectance of whitecaps, J. Geophys. Res., 109, C05021, doi:10.1029/2003JC002177, 2004.; Lauscher, F.: Sonnen- und Himmelstrahlu

 

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