Abstract

The effective reflectance of the foam on the ocean surface together with the fraction of the surface covered with foam describes the optical influence of whitecaps in the solar spectral range. This effective reflectance is found to be ~22% in the visible spectral range and is presented as a function of wavelength for the solar spectral range. With the fraction of the surface covered with foam, taken from the literature, the results lead to a good agreement with satellite measured radiances and albedo values. The effective reflectance is more than a factor of 2 lower than reflectance values used to date in remote sensing and radiation budget studies. Consequently, the optical influence of whitecaps can be assumed to be much less important than formerly supposed.

© 1984 Optical Society of America

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References

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  1. H. R. Gordon, M. M. Jacobs, “Albedo of the Ocean–Atmosphere System: Influence of Sea Foam,” Appl. Opt. 16, 2257 (1977).
    [CrossRef] [PubMed]
  2. P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Wavelength,” J. Geophys. Res. 86, 9801 (1981); Correction 87, 7350 (1982).
    [CrossRef]
  3. S. Tassan, “The Influence of Wind in the Remote Sensing of Chlorophyll in the Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 371.
    [CrossRef]
  4. P. Koepke, H. Quenzel, “Most Suitable Conditions for Aerosol Monitoring from Space,” Adv. Space Res. 2, 29 (1982).
    [CrossRef]
  5. R. W. Austin, S. Moran, “Reflectance of Whitecaps, Foam and Spray,” in Ocean Color Analysis (U. California, VIS-Lab., San Diego, 1974), SIO Ref. 74-10.
  6. D. C. Blanchard, “Whitecaps at Sea,” J. Atmos. Sci. 28, 645 (1971).
    [CrossRef]
  7. E. C. Monahan, “Oceanic Whitecaps,” J. Phys. Ocean 1, 139 (1971).
    [CrossRef]
  8. Y. Toba, M. Chaen, “Quantitative Expression of the Breaking of Wind Waves on the Sea Surface,” Rec. Oceanogr. Works Jpn. 12, 1 (1973).
  9. D. B. Ross, V. Cardone, “Observations of Oceanic Whitecaps and Their Relation to Remote Measurements of Surface Wind Speed,” J. Geophys. Res. 79, 444 (1974).
    [CrossRef]
  10. J. Wu, “Oceanic Whitecaps and Sea State,” J. Phys. Ocean 9, 1064 (1979).
    [CrossRef]
  11. E. C. Monahan, I. O’Muircheartaigh, “Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed,” J. Phys. Ocean 10, 2094 (1980).
    [CrossRef]
  12. G. A. Maul, H. R. Gordon, “On the Use of the Earth Resources Technology Satellite (LANDSAT-1) in Optical Oceanography,” Remote Sensing Environ. 4, 95 (1975).
    [CrossRef]
  13. W. M. Irvine, J. B. Pollack, “Infrared Optical Properties of Water and Ice Spheres,” Icarus 8, 324 (1968).
    [CrossRef]
  14. P. M. Saunders, “Shadowing on the Ocean and the Existence of the Horizon,” J. Geophys. Res. 72, 4643 (1967).
    [CrossRef]
  15. G. N. Plass, G. W. Kattawar, J. A. Guinn, “Isophotes of Sunlight Glitter on a Wind-Ruffled Sea,” Appl. Opt. 16, 643 (1977).
    [CrossRef] [PubMed]
  16. C. Cox, W. Munk, “Statistics of the Sea Surface Derived from Sun Glitter,” J. Mar. Res. 13, 198 (1954).
  17. A. Morel, “In-Water and Remote Measurements of Ocean Color,” Boundary-Layer Meteorol. 18, 177 (1980).
    [CrossRef]
  18. H. R. Gordon, “Radiative Transfer: Technique for Simulating the Ocean in Satellite Remote Sensing Calculations,” Appl. Opt. 15, 1974 (1976).
    [CrossRef] [PubMed]
  19. C. H. Whitlock, L. R. Poole, J. W. Usry, W. M. Houghton, W. G. Witte, W. D. Morris, E. A. Gurganus, “Comparison of Reflectance with Backscatter and Absorption Parameters for Turbid Waters,” Appl. Opt. 20, 517 (1981).
    [CrossRef] [PubMed]
  20. C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
    [CrossRef]
  21. P. J. Stabeno, E. C. Monahan, “The Influence of Whitecaps on the Albedo of the Sea Surface,” in Whitecaps and the Marine Atmosphere, Report 5, University College, Galway, Ireland (1983).
  22. P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Viewing Geometry,” J. Geophys. Res. 84, 7847 (1979).
    [CrossRef]
  23. H. Quenzel, M. Kaestner, “Optical Properties of the Atmosphere: Calculated Variability and Application to Satellite Remote Sensing of Phytoplankton,” Appl. Opt. 19, 1338 (1980).
    [CrossRef] [PubMed]
  24. E. C. Monahan, M. C. Spillane, P. J. Stabeno, personal communication at the “Whitecap Workshop,” 4–7 Sept. 1983, University College, Galway, Ireland (1983).
  25. Y. Miyake, T. Abe, “A Study on the Foaming of Sea Water,” J. Mar. Res. 7, 67 (1948).
  26. P. Koepke, “Vicarious Satellite Calibration in the Solar Spectral Range by Means of Calculated Radiances and Its Applrcation to Meteosat,” Appl. Opt. 21, 2845 (1982).
    [CrossRef] [PubMed]
  27. S. Sethuraman, G. S. Raynor, “Surface Drag Coefficient Dependence of the Aerodynamic Roughness of the Sea,” J. Geophys. Res. 80, 4983 (1975).
    [CrossRef]
  28. R. E. Payne, “Albedo of the Sea Surface,” J. Atmos. Sci. 29, 959 (1972).
    [CrossRef]
  29. NASA-ERTS Data Users Handbook, Document Nr. 71 SP 4249, Goddard Space Flight Center, Greenbelt, Md. (1971).
  30. M. Viollier, N. Baussart, P. Y. Deschamps, “Preliminary Results of CZCS Nimbus-7 Experiment for Ocean Colour Remote Sensing: Observation of the Ligurian Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 387.
    [CrossRef]

1982 (3)

P. Koepke, H. Quenzel, “Most Suitable Conditions for Aerosol Monitoring from Space,” Adv. Space Res. 2, 29 (1982).
[CrossRef]

C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
[CrossRef]

P. Koepke, “Vicarious Satellite Calibration in the Solar Spectral Range by Means of Calculated Radiances and Its Applrcation to Meteosat,” Appl. Opt. 21, 2845 (1982).
[CrossRef] [PubMed]

1981 (2)

C. H. Whitlock, L. R. Poole, J. W. Usry, W. M. Houghton, W. G. Witte, W. D. Morris, E. A. Gurganus, “Comparison of Reflectance with Backscatter and Absorption Parameters for Turbid Waters,” Appl. Opt. 20, 517 (1981).
[CrossRef] [PubMed]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Wavelength,” J. Geophys. Res. 86, 9801 (1981); Correction 87, 7350 (1982).
[CrossRef]

1980 (3)

E. C. Monahan, I. O’Muircheartaigh, “Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed,” J. Phys. Ocean 10, 2094 (1980).
[CrossRef]

A. Morel, “In-Water and Remote Measurements of Ocean Color,” Boundary-Layer Meteorol. 18, 177 (1980).
[CrossRef]

H. Quenzel, M. Kaestner, “Optical Properties of the Atmosphere: Calculated Variability and Application to Satellite Remote Sensing of Phytoplankton,” Appl. Opt. 19, 1338 (1980).
[CrossRef] [PubMed]

1979 (2)

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Viewing Geometry,” J. Geophys. Res. 84, 7847 (1979).
[CrossRef]

J. Wu, “Oceanic Whitecaps and Sea State,” J. Phys. Ocean 9, 1064 (1979).
[CrossRef]

1977 (2)

1976 (1)

1975 (2)

S. Sethuraman, G. S. Raynor, “Surface Drag Coefficient Dependence of the Aerodynamic Roughness of the Sea,” J. Geophys. Res. 80, 4983 (1975).
[CrossRef]

G. A. Maul, H. R. Gordon, “On the Use of the Earth Resources Technology Satellite (LANDSAT-1) in Optical Oceanography,” Remote Sensing Environ. 4, 95 (1975).
[CrossRef]

1974 (1)

D. B. Ross, V. Cardone, “Observations of Oceanic Whitecaps and Their Relation to Remote Measurements of Surface Wind Speed,” J. Geophys. Res. 79, 444 (1974).
[CrossRef]

1973 (1)

Y. Toba, M. Chaen, “Quantitative Expression of the Breaking of Wind Waves on the Sea Surface,” Rec. Oceanogr. Works Jpn. 12, 1 (1973).

1972 (1)

R. E. Payne, “Albedo of the Sea Surface,” J. Atmos. Sci. 29, 959 (1972).
[CrossRef]

1971 (2)

D. C. Blanchard, “Whitecaps at Sea,” J. Atmos. Sci. 28, 645 (1971).
[CrossRef]

E. C. Monahan, “Oceanic Whitecaps,” J. Phys. Ocean 1, 139 (1971).
[CrossRef]

1968 (1)

W. M. Irvine, J. B. Pollack, “Infrared Optical Properties of Water and Ice Spheres,” Icarus 8, 324 (1968).
[CrossRef]

1967 (1)

P. M. Saunders, “Shadowing on the Ocean and the Existence of the Horizon,” J. Geophys. Res. 72, 4643 (1967).
[CrossRef]

1954 (1)

C. Cox, W. Munk, “Statistics of the Sea Surface Derived from Sun Glitter,” J. Mar. Res. 13, 198 (1954).

1948 (1)

Y. Miyake, T. Abe, “A Study on the Foaming of Sea Water,” J. Mar. Res. 7, 67 (1948).

Abe, T.

Y. Miyake, T. Abe, “A Study on the Foaming of Sea Water,” J. Mar. Res. 7, 67 (1948).

Austin, R. W.

R. W. Austin, S. Moran, “Reflectance of Whitecaps, Foam and Spray,” in Ocean Color Analysis (U. California, VIS-Lab., San Diego, 1974), SIO Ref. 74-10.

Bartlett, D. S.

C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
[CrossRef]

Baussart, N.

M. Viollier, N. Baussart, P. Y. Deschamps, “Preliminary Results of CZCS Nimbus-7 Experiment for Ocean Colour Remote Sensing: Observation of the Ligurian Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 387.
[CrossRef]

Blanchard, D. C.

D. C. Blanchard, “Whitecaps at Sea,” J. Atmos. Sci. 28, 645 (1971).
[CrossRef]

Cardone, V.

D. B. Ross, V. Cardone, “Observations of Oceanic Whitecaps and Their Relation to Remote Measurements of Surface Wind Speed,” J. Geophys. Res. 79, 444 (1974).
[CrossRef]

Chaen, M.

Y. Toba, M. Chaen, “Quantitative Expression of the Breaking of Wind Waves on the Sea Surface,” Rec. Oceanogr. Works Jpn. 12, 1 (1973).

Cox, C.

C. Cox, W. Munk, “Statistics of the Sea Surface Derived from Sun Glitter,” J. Mar. Res. 13, 198 (1954).

Deschamps, P. Y.

M. Viollier, N. Baussart, P. Y. Deschamps, “Preliminary Results of CZCS Nimbus-7 Experiment for Ocean Colour Remote Sensing: Observation of the Ligurian Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 387.
[CrossRef]

Gordon, H. R.

Guinn, J. A.

Gurganus, E. A.

C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
[CrossRef]

C. H. Whitlock, L. R. Poole, J. W. Usry, W. M. Houghton, W. G. Witte, W. D. Morris, E. A. Gurganus, “Comparison of Reflectance with Backscatter and Absorption Parameters for Turbid Waters,” Appl. Opt. 20, 517 (1981).
[CrossRef] [PubMed]

Houghton, W. M.

Irvine, W. M.

W. M. Irvine, J. B. Pollack, “Infrared Optical Properties of Water and Ice Spheres,” Icarus 8, 324 (1968).
[CrossRef]

Jacobs, M. M.

Kaestner, M.

Kattawar, G. W.

Koepke, P.

P. Koepke, “Vicarious Satellite Calibration in the Solar Spectral Range by Means of Calculated Radiances and Its Applrcation to Meteosat,” Appl. Opt. 21, 2845 (1982).
[CrossRef] [PubMed]

P. Koepke, H. Quenzel, “Most Suitable Conditions for Aerosol Monitoring from Space,” Adv. Space Res. 2, 29 (1982).
[CrossRef]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Wavelength,” J. Geophys. Res. 86, 9801 (1981); Correction 87, 7350 (1982).
[CrossRef]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Viewing Geometry,” J. Geophys. Res. 84, 7847 (1979).
[CrossRef]

Maul, G. A.

G. A. Maul, H. R. Gordon, “On the Use of the Earth Resources Technology Satellite (LANDSAT-1) in Optical Oceanography,” Remote Sensing Environ. 4, 95 (1975).
[CrossRef]

Miyake, Y.

Y. Miyake, T. Abe, “A Study on the Foaming of Sea Water,” J. Mar. Res. 7, 67 (1948).

Monahan, E. C.

E. C. Monahan, I. O’Muircheartaigh, “Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed,” J. Phys. Ocean 10, 2094 (1980).
[CrossRef]

E. C. Monahan, “Oceanic Whitecaps,” J. Phys. Ocean 1, 139 (1971).
[CrossRef]

P. J. Stabeno, E. C. Monahan, “The Influence of Whitecaps on the Albedo of the Sea Surface,” in Whitecaps and the Marine Atmosphere, Report 5, University College, Galway, Ireland (1983).

E. C. Monahan, M. C. Spillane, P. J. Stabeno, personal communication at the “Whitecap Workshop,” 4–7 Sept. 1983, University College, Galway, Ireland (1983).

Moran, S.

R. W. Austin, S. Moran, “Reflectance of Whitecaps, Foam and Spray,” in Ocean Color Analysis (U. California, VIS-Lab., San Diego, 1974), SIO Ref. 74-10.

Morel, A.

A. Morel, “In-Water and Remote Measurements of Ocean Color,” Boundary-Layer Meteorol. 18, 177 (1980).
[CrossRef]

Morris, W. D.

Munk, W.

C. Cox, W. Munk, “Statistics of the Sea Surface Derived from Sun Glitter,” J. Mar. Res. 13, 198 (1954).

O’Muircheartaigh, I.

E. C. Monahan, I. O’Muircheartaigh, “Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed,” J. Phys. Ocean 10, 2094 (1980).
[CrossRef]

Payne, R. E.

R. E. Payne, “Albedo of the Sea Surface,” J. Atmos. Sci. 29, 959 (1972).
[CrossRef]

Plass, G. N.

Pollack, J. B.

W. M. Irvine, J. B. Pollack, “Infrared Optical Properties of Water and Ice Spheres,” Icarus 8, 324 (1968).
[CrossRef]

Poole, L. R.

Quenzel, H.

P. Koepke, H. Quenzel, “Most Suitable Conditions for Aerosol Monitoring from Space,” Adv. Space Res. 2, 29 (1982).
[CrossRef]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Wavelength,” J. Geophys. Res. 86, 9801 (1981); Correction 87, 7350 (1982).
[CrossRef]

H. Quenzel, M. Kaestner, “Optical Properties of the Atmosphere: Calculated Variability and Application to Satellite Remote Sensing of Phytoplankton,” Appl. Opt. 19, 1338 (1980).
[CrossRef] [PubMed]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Viewing Geometry,” J. Geophys. Res. 84, 7847 (1979).
[CrossRef]

Raynor, G. S.

S. Sethuraman, G. S. Raynor, “Surface Drag Coefficient Dependence of the Aerodynamic Roughness of the Sea,” J. Geophys. Res. 80, 4983 (1975).
[CrossRef]

Ross, D. B.

D. B. Ross, V. Cardone, “Observations of Oceanic Whitecaps and Their Relation to Remote Measurements of Surface Wind Speed,” J. Geophys. Res. 79, 444 (1974).
[CrossRef]

Saunders, P. M.

P. M. Saunders, “Shadowing on the Ocean and the Existence of the Horizon,” J. Geophys. Res. 72, 4643 (1967).
[CrossRef]

Sethuraman, S.

S. Sethuraman, G. S. Raynor, “Surface Drag Coefficient Dependence of the Aerodynamic Roughness of the Sea,” J. Geophys. Res. 80, 4983 (1975).
[CrossRef]

Spillane, M. C.

E. C. Monahan, M. C. Spillane, P. J. Stabeno, personal communication at the “Whitecap Workshop,” 4–7 Sept. 1983, University College, Galway, Ireland (1983).

Stabeno, P. J.

E. C. Monahan, M. C. Spillane, P. J. Stabeno, personal communication at the “Whitecap Workshop,” 4–7 Sept. 1983, University College, Galway, Ireland (1983).

P. J. Stabeno, E. C. Monahan, “The Influence of Whitecaps on the Albedo of the Sea Surface,” in Whitecaps and the Marine Atmosphere, Report 5, University College, Galway, Ireland (1983).

Tassan, S.

S. Tassan, “The Influence of Wind in the Remote Sensing of Chlorophyll in the Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 371.
[CrossRef]

Toba, Y.

Y. Toba, M. Chaen, “Quantitative Expression of the Breaking of Wind Waves on the Sea Surface,” Rec. Oceanogr. Works Jpn. 12, 1 (1973).

Usry, J. W.

Viollier, M.

M. Viollier, N. Baussart, P. Y. Deschamps, “Preliminary Results of CZCS Nimbus-7 Experiment for Ocean Colour Remote Sensing: Observation of the Ligurian Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 387.
[CrossRef]

Whitlock, C. H.

C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
[CrossRef]

C. H. Whitlock, L. R. Poole, J. W. Usry, W. M. Houghton, W. G. Witte, W. D. Morris, E. A. Gurganus, “Comparison of Reflectance with Backscatter and Absorption Parameters for Turbid Waters,” Appl. Opt. 20, 517 (1981).
[CrossRef] [PubMed]

Witte, W. G.

Wu, J.

J. Wu, “Oceanic Whitecaps and Sea State,” J. Phys. Ocean 9, 1064 (1979).
[CrossRef]

Adv. Space Res. (1)

P. Koepke, H. Quenzel, “Most Suitable Conditions for Aerosol Monitoring from Space,” Adv. Space Res. 2, 29 (1982).
[CrossRef]

Appl. Opt. (6)

Boundary-Layer Meteorol. (1)

A. Morel, “In-Water and Remote Measurements of Ocean Color,” Boundary-Layer Meteorol. 18, 177 (1980).
[CrossRef]

Geophys. Res. Lett. (1)

C. H. Whitlock, D. S. Bartlett, E. A. Gurganus, “Sea Foam Reflectance and Influence on Optimum Wavelength for Remote Sensing of Ocean Aerosols,” Geophys. Res. Lett. 9, 719 (1982).
[CrossRef]

Icarus (1)

W. M. Irvine, J. B. Pollack, “Infrared Optical Properties of Water and Ice Spheres,” Icarus 8, 324 (1968).
[CrossRef]

J. Atmos. Sci. (2)

D. C. Blanchard, “Whitecaps at Sea,” J. Atmos. Sci. 28, 645 (1971).
[CrossRef]

R. E. Payne, “Albedo of the Sea Surface,” J. Atmos. Sci. 29, 959 (1972).
[CrossRef]

J. Geophys. Res. (5)

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Viewing Geometry,” J. Geophys. Res. 84, 7847 (1979).
[CrossRef]

S. Sethuraman, G. S. Raynor, “Surface Drag Coefficient Dependence of the Aerodynamic Roughness of the Sea,” J. Geophys. Res. 80, 4983 (1975).
[CrossRef]

P. M. Saunders, “Shadowing on the Ocean and the Existence of the Horizon,” J. Geophys. Res. 72, 4643 (1967).
[CrossRef]

P. Koepke, H. Quenzel, “Turbidity of the Atmosphere Determined from Satellite: Calculation of Optimum Wavelength,” J. Geophys. Res. 86, 9801 (1981); Correction 87, 7350 (1982).
[CrossRef]

D. B. Ross, V. Cardone, “Observations of Oceanic Whitecaps and Their Relation to Remote Measurements of Surface Wind Speed,” J. Geophys. Res. 79, 444 (1974).
[CrossRef]

J. Mar. Res. (2)

C. Cox, W. Munk, “Statistics of the Sea Surface Derived from Sun Glitter,” J. Mar. Res. 13, 198 (1954).

Y. Miyake, T. Abe, “A Study on the Foaming of Sea Water,” J. Mar. Res. 7, 67 (1948).

J. Phys. Ocean (3)

J. Wu, “Oceanic Whitecaps and Sea State,” J. Phys. Ocean 9, 1064 (1979).
[CrossRef]

E. C. Monahan, I. O’Muircheartaigh, “Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed,” J. Phys. Ocean 10, 2094 (1980).
[CrossRef]

E. C. Monahan, “Oceanic Whitecaps,” J. Phys. Ocean 1, 139 (1971).
[CrossRef]

Rec. Oceanogr. Works Jpn. (1)

Y. Toba, M. Chaen, “Quantitative Expression of the Breaking of Wind Waves on the Sea Surface,” Rec. Oceanogr. Works Jpn. 12, 1 (1973).

Remote Sensing Environ. (1)

G. A. Maul, H. R. Gordon, “On the Use of the Earth Resources Technology Satellite (LANDSAT-1) in Optical Oceanography,” Remote Sensing Environ. 4, 95 (1975).
[CrossRef]

Other (6)

S. Tassan, “The Influence of Wind in the Remote Sensing of Chlorophyll in the Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 371.
[CrossRef]

R. W. Austin, S. Moran, “Reflectance of Whitecaps, Foam and Spray,” in Ocean Color Analysis (U. California, VIS-Lab., San Diego, 1974), SIO Ref. 74-10.

P. J. Stabeno, E. C. Monahan, “The Influence of Whitecaps on the Albedo of the Sea Surface,” in Whitecaps and the Marine Atmosphere, Report 5, University College, Galway, Ireland (1983).

NASA-ERTS Data Users Handbook, Document Nr. 71 SP 4249, Goddard Space Flight Center, Greenbelt, Md. (1971).

M. Viollier, N. Baussart, P. Y. Deschamps, “Preliminary Results of CZCS Nimbus-7 Experiment for Ocean Colour Remote Sensing: Observation of the Ligurian Sea,” in Oceanography from Space, J. Gower, Ed. (Plenum, New York, 1981), p. 387.
[CrossRef]

E. C. Monahan, M. C. Spillane, P. J. Stabeno, personal communication at the “Whitecap Workshop,” 4–7 Sept. 1983, University College, Galway, Ireland (1983).

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Figures (8)

Fig. 1
Fig. 1

Examples of the variation of a whitecap at 1-sec intervals, beginning at an age of 0.5 sec with an uncertainty of ±0.5 sec: wind speed, 7.5 m · sec−1; water temperature, 15.7 °C; viewing elevation, 60°; distance to foam patch, 35 m.

Fig. 2
Fig. 2

Examples of the variation of an ocean surface with foam streaks at 1-sec intervals: wind speed, 14.5 m · sec−1, water temperature, 15.7° C; viewing elevation, 50°; distance to the center of the image, 50 m.

Fig. 3
Fig. 3

Normalized area of whitecaps (foam patches) as a function of their age. The thicker stripes give the mean values. Wind speed between 7.5 and 8.5 m · sec−1; water temperature between 15 and 16°C. The curve is calculated from Eq. (10) with β = 0.25 and γ = 1.

Fig. 4
Fig. 4

Normalized area of foam streaks as a function of their age. The thicker stripes give the mean values. Wind speed between 14 and 15 m · sec−1; water temperature between 15 and 16°C. The curve is calculated from Eq. (10) with β = 0.7 and γ = 0.4.

Fig. 5
Fig. 5

Reflectance of whitecaps (foam patches) in the visible spectral range as a function of their age. The thicker stripes give the mean values. Maximum reflectance of fresh dense foam Rf = 55% after Whitlock et al.20 Other data as in Fig. 3.

Fig. 6
Fig. 6

Reflectance of foam streaks in the visible spectral range as a function of their age. Other data as in Fig. 4.

Fig. 7
Fig. 7

fef values as a function of wind speed U. The numbers at the curves indicate what proportion x of the fraction of foam streaks is assumed to be taken into account in the W(U) values; see text.

Fig. 8
Fig. 8

Effective reflectance of oceanic foam as a function of wavelength, after Eq. (9).

Tables (2)

Tables Icon

Table I Effective Reflectance in the Visible Spectral Range and Efficiency Factor Independent of Wavelength as a Function of Age τ of Individual Whitecaps (See Text)

Tables Icon

Table II Wind Speed Dependent Values of the Area Covered with Foam W(U), the Efficiency Factor fef(U), the Effective Reflectance in the Visible Spectral Range Ref(U), and the Total Reflectance Due to Foam Rt,tot(U) in this Spectral Range

Equations (21)

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R o c = R f , tot + ( 1 - W ) · R s + ( 1 - R f , tot ) · R u .
W = α · U λ ,
W = 2.95 10 - 6 · U 3.52 ,
R t , tot = W · R f .
R f , tot = W · R ef .
R f , tot ( λ ) = W · f ef · R f ( λ ) .
R ef = 0 τ a ( t ) · r ( t ) · d t 0 τ a ( t ) · d t .
f ef = R ef R f = R ef 0.55 .
R ef ( λ ) = f ef · R f ( λ ) ,
a ( t ) = 1 - exp ( - β · t γ ) ,
R ef , p = ( 22 ± 8 ) % , f ef , p = 0.4 ± 0.15.
R ef , s = ( 10 ± 4 ) % , f ef , s = 0.18 ± 0.07.
R t , tot = R f · ( W p · f ef , p + W s · f ef , s ) .
S P = W s / W p .
S P = 0 , U 8.5 m · sec - 1 , S P = - 2.1 + 0.24 · U , U < 8.5 m · sec - 1 .
W ( U ) = W p ( U ) + x · W s ( U ) .
W p ( U ) = W ( U ) / [ 1 + x · S P ( U ) ] , W s ( U ) = W ( U ) · S P ( U ) / [ 1 + x · S P ( U ) ] .
R f , tot ( U ) = W ( U ) · f ef ( U ) · R f = W ( U ) · R ef ( U ) ,
f ef ( U ) = [ f ef , p + f ef , s · S P ( U ) ] / [ 1 + x · S P ( U ) ] .
f ef ( U ) = 0.4 ± 0.2 ,             R ef ( U ) = ( 22 ± 11 ) % .
a = i = 1 I a i r = i = 1 I a i · r i / i = 1 I a i .

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