Abstract

The oldest record of ocean color measurements consists of visual comparisons to a standardized color scale, the Forel-Ule scale (FU). Analysis of FU archived data allows the construction of a century-long time series. In situ protocols of FU measurements require the perceived color to be estimated over the water column above a Secchi disk (SD) at half of the depth where it goes out of sight, whereas satellites retrieve FU over the water column alone. I show in this article that these two methodologies lead to different FU readings and thus, merging both kinds of data will create artificial trends. In case 1 waters, radiative transfer simulations show that measuring over a SD shifts FU between 0 and + 2 in respect to no SD, and there exists no possibility to relate the two in a univocal fashion. A univocal relationship is found if color is expressed in terms of the hue angle, which can be calculated from light spectra or RGB images.

© 2017 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Deriving inherent optical properties from classical water color measurements: Forel-Ule index and Secchi disk depth

Shenglei Wang, Zhongping Lee, Shaoling Shang, Junsheng Li, Bing Zhang, and Gong Lin
Opt. Express 27(5) 7642-7655 (2019)

Why does the Secchi disk disappear? An imaging perspective

Weilin Hou, Zhongping Lee, and Alan D. Weidemann
Opt. Express 15(6) 2791-2802 (2007)

Secchi disk observation with spectral-selective glasses in blue and green waters

Zhongping Lee, Shaoling Shang, Gong Lin, Tongtong Liu, Yangyang Liu, Keping Du, and Kelly Luis
Opt. Express 25(17) 19878-19885 (2017)

References

  • View by:
  • |
  • |
  • |

  1. ESA-OC-CCI, “Product User Guide” (2017), retrieved http://www.esa-oceancolour-cci.org/?q=webfm_send/684 .
  2. M. R. Wernand and H. J. van der Woerd, “Ocean colour changes in the North Pacific since 1930,” J. Eur. Opt. Soc. Rap. Public 5(2010).
  3. M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
    [PubMed]
  4. M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).
  5. D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).
  6. H. J. Woerd and M. R. Wernand, “True Colour Classification of Natural Waters With Medium-Spectral Resolution Satellites: SeaWiFS, MODIS, MERIS and OLCI,” Sensors (Basel) 15(10), 25663–25680 (2015).
    [PubMed]
  7. G. E. Hutchinson, “Limnological Studies in Indian Tibet,” Int. Rev. Gesamten Hydrobiol. Hydrograph. 35, 134–177 (1937).
  8. C. D. Mobley and L. K. Sundman, Hydrolight 5 Ecolight 5 Technical Documentation (Sequoia Sci., Inc., Bellevue, WA, 2008), p. 100.
  9. R. W. Preisendorfer, “Secchi disk science: Visual optics of natural waters,” Limnol. Oceanogr. 31, 909–926 (1986).
  10. Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).
  11. A. Morel, “Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters),” Journal of Geophysical Research: Oceans 93, 10749–10768 (1988).
  12. A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).
  13. P. J. Werdell, “Ocean color chlorophyll (OC) v6” (NASA Ocean Biology Processing Group., 2010), retrieved 2009, http://oceancolor.gsfc.nasa.gov/REPROCESSING/R2009/ocv6/ .
  14. P. J. Werdell and S. W. Bailey, “An improved in-situ bio-optical data set for ocean color algorithm development and satellite data product validation,” Remote Sens. Environ. 98, 122–140 (2005).
  15. A. Morel, “Are the empirical relationships describing the bio-optical properties of case 1 waters consistent and internally compatible?,” Journal of Geophysical Research: Oceans 114, n/a-n/a (2009).
  16. A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

2015 (2)

H. J. Woerd and M. R. Wernand, “True Colour Classification of Natural Waters With Medium-Spectral Resolution Satellites: SeaWiFS, MODIS, MERIS and OLCI,” Sensors (Basel) 15(10), 25663–25680 (2015).
[PubMed]

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

2013 (2)

M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
[PubMed]

M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).

2012 (1)

D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).

2010 (1)

A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

2005 (1)

P. J. Werdell and S. W. Bailey, “An improved in-situ bio-optical data set for ocean color algorithm development and satellite data product validation,” Remote Sens. Environ. 98, 122–140 (2005).

1998 (1)

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

1988 (1)

A. Morel, “Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters),” Journal of Geophysical Research: Oceans 93, 10749–10768 (1988).

1986 (1)

R. W. Preisendorfer, “Secchi disk science: Visual optics of natural waters,” Limnol. Oceanogr. 31, 909–926 (1986).

1937 (1)

G. E. Hutchinson, “Limnological Studies in Indian Tibet,” Int. Rev. Gesamten Hydrobiol. Hydrograph. 35, 134–177 (1937).

Allali, K.

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

Babin, M.

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

Bailey, S. W.

P. J. Werdell and S. W. Bailey, “An improved in-situ bio-optical data set for ocean color algorithm development and satellite data product validation,” Remote Sens. Environ. 98, 122–140 (2005).

Boyce, D. G.

D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).

Bricaud, A.

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

Claustre, H.

A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

Du, K.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Gentili, B.

A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

Gieskes, W. W. C.

M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
[PubMed]

Hommersom, A.

M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).

Hou, W.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Hu, C.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Hutchinson, G. E.

G. E. Hutchinson, “Limnological Studies in Indian Tibet,” Int. Rev. Gesamten Hydrobiol. Hydrograph. 35, 134–177 (1937).

Lee, Z.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Lewis, M.

D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).

Lin, G.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Lin, J.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Morel, A.

A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

A. Morel, “Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters),” Journal of Geophysical Research: Oceans 93, 10749–10768 (1988).

Preisendorfer, R. W.

R. W. Preisendorfer, “Secchi disk science: Visual optics of natural waters,” Limnol. Oceanogr. 31, 909–926 (1986).

Shang, S.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

van der Woerd, H. J.

M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).

M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
[PubMed]

Weidemann, A.

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

Werdell, P. J.

P. J. Werdell and S. W. Bailey, “An improved in-situ bio-optical data set for ocean color algorithm development and satellite data product validation,” Remote Sens. Environ. 98, 122–140 (2005).

Wernand, M. R.

H. J. Woerd and M. R. Wernand, “True Colour Classification of Natural Waters With Medium-Spectral Resolution Satellites: SeaWiFS, MODIS, MERIS and OLCI,” Sensors (Basel) 15(10), 25663–25680 (2015).
[PubMed]

M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
[PubMed]

M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).

Woerd, H. J.

H. J. Woerd and M. R. Wernand, “True Colour Classification of Natural Waters With Medium-Spectral Resolution Satellites: SeaWiFS, MODIS, MERIS and OLCI,” Sensors (Basel) 15(10), 25663–25680 (2015).
[PubMed]

Worm, B.

D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).

Biogeosciences (1)

A. Morel, H. Claustre, and B. Gentili, “The most oligotrophic subtropical zones of the global ocean: similarities and differences in terms of chlorophyll and yellow substance,” Biogeosciences 7, 3139–3151 (2010).

Int. Rev. Gesamten Hydrobiol. Hydrograph. (1)

G. E. Hutchinson, “Limnological Studies in Indian Tibet,” Int. Rev. Gesamten Hydrobiol. Hydrograph. 35, 134–177 (1937).

J. Geophys. Res., C, Oceans (1)

A. Bricaud, A. Morel, M. Babin, K. Allali, and H. Claustre, “Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models,” J. Geophys. Res., C, Oceans 103, 31033–31044 (1998).

Journal of Geophysical Research: Oceans (1)

A. Morel, “Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters),” Journal of Geophysical Research: Oceans 93, 10749–10768 (1988).

Limnol. Oceanogr. (1)

R. W. Preisendorfer, “Secchi disk science: Visual optics of natural waters,” Limnol. Oceanogr. 31, 909–926 (1986).

Limnol. Oceanogr. Methods (1)

D. G. Boyce, M. Lewis, and B. Worm, “Integrating global chlorophyll data from 1890 to 2010,” Limnol. Oceanogr. Methods 10, 840–852 (2012).

Ocean Sci. (1)

M. R. Wernand, A. Hommersom, and H. J. van der Woerd, “MERIS-based ocean colour classification with the discrete Forel–Ule scale,” Ocean Sci. 9, 477–487 (2013).

PLoS One (1)

M. R. Wernand, H. J. van der Woerd, and W. W. C. Gieskes, “Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide,” PLoS One 8(6), e63766 (2013).
[PubMed]

Remote Sens. Environ. (2)

Z. Lee, S. Shang, C. Hu, K. Du, A. Weidemann, W. Hou, J. Lin, and G. Lin, “Secchi disk depth: A new theory and mechanistic model for underwater visibility,” Remote Sens. Environ. 169, 139–149 (2015).

P. J. Werdell and S. W. Bailey, “An improved in-situ bio-optical data set for ocean color algorithm development and satellite data product validation,” Remote Sens. Environ. 98, 122–140 (2005).

Sensors (Basel) (1)

H. J. Woerd and M. R. Wernand, “True Colour Classification of Natural Waters With Medium-Spectral Resolution Satellites: SeaWiFS, MODIS, MERIS and OLCI,” Sensors (Basel) 15(10), 25663–25680 (2015).
[PubMed]

Other (5)

C. D. Mobley and L. K. Sundman, Hydrolight 5 Ecolight 5 Technical Documentation (Sequoia Sci., Inc., Bellevue, WA, 2008), p. 100.

ESA-OC-CCI, “Product User Guide” (2017), retrieved http://www.esa-oceancolour-cci.org/?q=webfm_send/684 .

M. R. Wernand and H. J. van der Woerd, “Ocean colour changes in the North Pacific since 1930,” J. Eur. Opt. Soc. Rap. Public 5(2010).

A. Morel, “Are the empirical relationships describing the bio-optical properties of case 1 waters consistent and internally compatible?,” Journal of Geophysical Research: Oceans 114, n/a-n/a (2009).

P. J. Werdell, “Ocean color chlorophyll (OC) v6” (NASA Ocean Biology Processing Group., 2010), retrieved 2009, http://oceancolor.gsfc.nasa.gov/REPROCESSING/R2009/ocv6/ .

Cited By

OSA participates in Crossref's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (6)

Fig. 1
Fig. 1 Change in color over a Secchi disk (SD) at different depths. Panel a): CIE 1931 (x,y) coordinates of the remote-sensing reflectance for three different chlorophyll-a concentrations (see legend). Squares: infinite water column: Circles: SD at variable depths, until the surface. Diamonds: SD at zSD/2. Overlapped, in grey dots, the coordinates of the 21 FU colors. Panel b): remote-sensing reflectance for the case C = 0.2 mg m−3 in panel a).
Fig. 2
Fig. 2 a) A digital picture taken from a ship in the Mediterranean Sea of a Secchi disk in the water at zSD/2. b) Hue angle of the image, in degrees.
Fig. 3
Fig. 3 Maximum band ratio calculated from the EcoLight output Rrs using the “new case 1” model respect to the related chlorophyll concentration. Blue dots: using fy = 0.2, the default value in the model. Red dots: using fy = 0.6154, after Morel [15]. The OC4v6 curve [13] is added for comparison.
Fig. 4
Fig. 4 Brown line: fit by Wernand et al. [3] after EcoLight simulations with the “new case 1” model. Black line: fit by Boyce et al. [5] from matched in situ FU and chlorophyll data, for an infinite water column. Red squares: simulated FU values for the simulation setup described in the Methods section, for fy = 0.2 (default). Blue squares: same as the res squares, but using fy = 0.6154, after Morel [15], for an infinite water column. Green squares: same as the blue squares, but placing a Secchi disk at zSD/2 for each run, with zSD calculated according to Preisendorfer’s model [9]. Brown-green squares: same as the green squares, but with zSD calculated according to Lee’s model [10].
Fig. 5
Fig. 5 Differences in water color (FU in panel a) and Hue angle in Panel b)) derived from Ecolight simulations, using the “new case 1” bio-optical model with fy = 0.6154, after Morel [15], with and without a Secchi disk. In panel a), square size corresponds to the relative number of occurrences.
Fig. 6
Fig. 6 Difference in the calculated Hue angle the Remote sensing reflectance over a Secchi disk at zSD/2 respect to the Hue angle over an infinite water column. The least squares 9th degree polynomials fit are plotted as well.

Tables (2)

Tables Icon

Table 1 Forel-Ule index and Hue angle of simulated remote sensing reflectance for the simulation detailed in Fig. 1.

Tables Icon

Table 2 Coefficients (with 95% confidence bounds) and statistics of the best fit 9th degree polynomial over the data points in Fig. 6.

Metrics