In the thesis introduction issues are discussed on the historical background of marine optics and... more In the thesis introduction issues are discussed on the historical background of marine optics and on marine optical devices that were used over the past centuries to observe and measure; as in all sciences, in marine optics we can see a steady development: that of ‘measuring’, beginning many centuries ago, to 'knowing' and since less than a century to the understanding of the phenomenon. Hereafter, six themes are treated successively. The first theme, ‘Ocean optics from 1600 (Hudson) to 1930 (Raman), shift in interpretation of natural water colouring’, addresses the question of why it took so long a time to explain the phenomenon ‘the colouring of the sea’, especially the blue colour, despite the age-long interest of sailors, for practical purposes of navigation and detection of fish – of which more later. The second theme ‘On the history of the Secchi disc’, describes the search to establish methods for the determination of (sea) water clarity concerning purposes of navigat...
How is the color determined? By means of a Forel-Ule scale (historical method, 1890), from which ... more How is the color determined? By means of a Forel-Ule scale (historical method, 1890), from which the color is compared to the color above a submersed white disk (Secchi-disk) or by means of hyperspectral light meters Science Besides water temperature, salinity and clarity, 'the color of water' belongs to the oldest observations of lakes, seas and oceans. 'The color of water' is an essential climate variable defined by the World Meteorological Organization (WMO) Forel-Ule color composite of al observations done between 1890 en 2000. Color change of the North-Atlantic Ocean since 1890. This ocean is greening (by plankton, so more food) Color comparison between a painted and the color of the sea. How to determine the color of the sea from marine art? i) Using de Modern Forel-Ule color comparator scale (historical method, 1890) and compare with painted sea. ii) Taking a picture of the painted sea including Gray-scale. Then from RGB to XYZ to x,y chromaticity derived Fore...
Ground truth measurements ar necessary for the validation of remotely sensed data. Rapid ship or ... more Ground truth measurements ar necessary for the validation of remotely sensed data. Rapid ship or aircraft spectral measurements of the upwelling and downwelling radiance are needed to determine the reflectance of the water column as well as to intercalibrate with satellite sensors. Inter calibrations are hindered by the application of different instruments with varying spectral bands. It has been found
Participatory science is not, as perhaps is believed, something of the 21st century. In this manu... more Participatory science is not, as perhaps is believed, something of the 21st century. In this manuscript we show that over a century ago it were not only scientists who collected oceanographic data but also merchant sailors. A good example of such globally collected data are Forel-Ule observations, from which the first date back to 1889. This hardly explored (NOAA) dataset, containing around 228,000 of so-called ocean colour observations, was recently analysed on trends. Some of the material here presented refers to a recent publication ‘Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide’ (Wernand et al., 2013). Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans - but already since 1889. We provided evidence of the usefulness of the Forel-Ule scal...
ABSTRACT Introduction Framed within the European Project CITCLOPS (Citizens' Observat... more ABSTRACT Introduction Framed within the European Project CITCLOPS (Citizens' Observatory for Coast and Ocean Optical Monitoring), the aim of this study is to present a number of tools that can be employed by citizens to estimate the color of natural waters. Firstly, a scale that accurately matches the original Forel-Ule (FU) colors was developed using accessible and affordable materials. This Modern FU scale is presented as a 'Do-It-Yourself' kit that can be prepared using high-quality illumination filters and a frame made of a white Plexiglas (or other white material). Secondly, a smartphone application (APP) prototype that could be used by anyone willing to participate in environmental monitoring is presented. This application includes a digitalized color-comparator scale, simulating the colors of the original Forel-Ule scale, to be compared to the color of water bodies, and allows the observer to take a picture of the water body to calculate the FU number using a specific algorithm. It also offers an option to include a Secchi disk depth estimate and the Forel-Ule number obtained with the Modern FU scale, if the observer is in possession of these tools. The first inputs provided by selected volunteers and researchers, offer initial comparisons between the two monitoring tools, the Modern FU scale and the digital scale included in the smartphone application. The idea is to provide a water quality index appropriate for participatory science that allows for rapid estimates and interpretation of color changes occurring in the aquatic environment, and that could be used by local or global authorities as an assessing tool. Background
Deep Sea Research Part A. Oceanographic Research Papers, 1981
... Conseil Permanent International pour l'Exploration de la Mer, 38, 131-146. ... To keep t... more ... Conseil Permanent International pour l'Exploration de la Mer, 38, 131-146. ... To keep the errors minimal, one should decide whether to measure E+v = (Eo+E)/2 or E_v = (Eo-E)/2. Figure 6 displays variation of the function given by equation (2) for different radiance distributions in ...
ABSTRACT An intensive data collection campaign has been conducted in the coastal waters of the so... more ABSTRACT An intensive data collection campaign has been conducted in the coastal waters of the southern North Sea during which a variety of marine optical parameters have ben measured. This has enabled the angular distribution factor of spectral radiance or Q factor to be calculated from in situ measurements. The Q factor relates upwelled spectral radiance to upwelled spectral irradiance and its precise determination is of importance in ocean color remote sensing. Previous modeling studies, often based on the optical properties of case I waters, have proposed a value of 5 for Q. However, this study suggest that more turbid coastal waters may approach the Lambertian case of Q close to (pi) .
ABSTRACT In this chapter the ideas of explorers and scientists on transparency and colouring issu... more ABSTRACT In this chapter the ideas of explorers and scientists on transparency and colouring issues of natural waters are sketched over a period between 1600 and 1930, from the time of Sir Francis Bacon to Chandrasekhara Raman. This history features famous scientists as well as various amateurs who were intrigued by these optical phenomena. We also discuss are a number of pieces of interesting equipment that were developed to quantify the intrinsically coupled transparency and colour of the sea. The Secchi disc (to determine water transparency) and the Forel–Ule scale (to classify sea and colour) are two, from the end of the nineteenth century, which have withstood the time. The hidden mechanisms for the colouring of water were only solved at the beginning of the twentieth century. It is argued that this delay was partially caused by the fact that the subject was mostly treated as marginal; also, if pure water distillation techniques had been fully developed earlier, this understanding could have been shifted backwards by decades. This chapter ends with Chandrasekhara Venkata Raman, who proved in 1922 that molecular scattering of light in water, in combination with the absorption of the longer wavelengths, caused the blue colour of the sea. In his Nobel lecture ‘On the colour of the sea’ on December 11, 1930 he explained his findings to the world.
. Ground truth measurements are necessary for the validation of remotely sensed data. Rapid ship ... more . Ground truth measurements are necessary for the validation of remotely sensed data. Rapid ship or aircraft spectral measurements of the upwelling and downwelling (ir)radiance are needed to determine the reflectance of the water column as well, as to intercalibrate with satellite ...
Using an optical multichannel analyzer, 168 downswelling irradiance spectra were obtained in vari... more Using an optical multichannel analyzer, 168 downswelling irradiance spectra were obtained in variable atmospheric solar, and cloud cover conditions, and with solar elevations varying between 30 and 60 deg, to retrieve the total spectra in the visible 400-720 nm range. The accuracy of the retrieval is found to be better than that of the determination of some ground truth parameters
In the thesis introduction issues are discussed on the historical background of marine optics and... more In the thesis introduction issues are discussed on the historical background of marine optics and on marine optical devices that were used over the past centuries to observe and measure; as in all sciences, in marine optics we can see a steady development: that of ‘measuring’, beginning many centuries ago, to 'knowing' and since less than a century to the understanding of the phenomenon. Hereafter, six themes are treated successively. The first theme, ‘Ocean optics from 1600 (Hudson) to 1930 (Raman), shift in interpretation of natural water colouring’, addresses the question of why it took so long a time to explain the phenomenon ‘the colouring of the sea’, especially the blue colour, despite the age-long interest of sailors, for practical purposes of navigation and detection of fish – of which more later. The second theme ‘On the history of the Secchi disc’, describes the search to establish methods for the determination of (sea) water clarity concerning purposes of navigat...
How is the color determined? By means of a Forel-Ule scale (historical method, 1890), from which ... more How is the color determined? By means of a Forel-Ule scale (historical method, 1890), from which the color is compared to the color above a submersed white disk (Secchi-disk) or by means of hyperspectral light meters Science Besides water temperature, salinity and clarity, 'the color of water' belongs to the oldest observations of lakes, seas and oceans. 'The color of water' is an essential climate variable defined by the World Meteorological Organization (WMO) Forel-Ule color composite of al observations done between 1890 en 2000. Color change of the North-Atlantic Ocean since 1890. This ocean is greening (by plankton, so more food) Color comparison between a painted and the color of the sea. How to determine the color of the sea from marine art? i) Using de Modern Forel-Ule color comparator scale (historical method, 1890) and compare with painted sea. ii) Taking a picture of the painted sea including Gray-scale. Then from RGB to XYZ to x,y chromaticity derived Fore...
Ground truth measurements ar necessary for the validation of remotely sensed data. Rapid ship or ... more Ground truth measurements ar necessary for the validation of remotely sensed data. Rapid ship or aircraft spectral measurements of the upwelling and downwelling radiance are needed to determine the reflectance of the water column as well as to intercalibrate with satellite sensors. Inter calibrations are hindered by the application of different instruments with varying spectral bands. It has been found
Participatory science is not, as perhaps is believed, something of the 21st century. In this manu... more Participatory science is not, as perhaps is believed, something of the 21st century. In this manuscript we show that over a century ago it were not only scientists who collected oceanographic data but also merchant sailors. A good example of such globally collected data are Forel-Ule observations, from which the first date back to 1889. This hardly explored (NOAA) dataset, containing around 228,000 of so-called ocean colour observations, was recently analysed on trends. Some of the material here presented refers to a recent publication ‘Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide’ (Wernand et al., 2013). Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans - but already since 1889. We provided evidence of the usefulness of the Forel-Ule scal...
ABSTRACT Introduction Framed within the European Project CITCLOPS (Citizens' Observat... more ABSTRACT Introduction Framed within the European Project CITCLOPS (Citizens' Observatory for Coast and Ocean Optical Monitoring), the aim of this study is to present a number of tools that can be employed by citizens to estimate the color of natural waters. Firstly, a scale that accurately matches the original Forel-Ule (FU) colors was developed using accessible and affordable materials. This Modern FU scale is presented as a 'Do-It-Yourself' kit that can be prepared using high-quality illumination filters and a frame made of a white Plexiglas (or other white material). Secondly, a smartphone application (APP) prototype that could be used by anyone willing to participate in environmental monitoring is presented. This application includes a digitalized color-comparator scale, simulating the colors of the original Forel-Ule scale, to be compared to the color of water bodies, and allows the observer to take a picture of the water body to calculate the FU number using a specific algorithm. It also offers an option to include a Secchi disk depth estimate and the Forel-Ule number obtained with the Modern FU scale, if the observer is in possession of these tools. The first inputs provided by selected volunteers and researchers, offer initial comparisons between the two monitoring tools, the Modern FU scale and the digital scale included in the smartphone application. The idea is to provide a water quality index appropriate for participatory science that allows for rapid estimates and interpretation of color changes occurring in the aquatic environment, and that could be used by local or global authorities as an assessing tool. Background
Deep Sea Research Part A. Oceanographic Research Papers, 1981
... Conseil Permanent International pour l'Exploration de la Mer, 38, 131-146. ... To keep t... more ... Conseil Permanent International pour l'Exploration de la Mer, 38, 131-146. ... To keep the errors minimal, one should decide whether to measure E+v = (Eo+E)/2 or E_v = (Eo-E)/2. Figure 6 displays variation of the function given by equation (2) for different radiance distributions in ...
ABSTRACT An intensive data collection campaign has been conducted in the coastal waters of the so... more ABSTRACT An intensive data collection campaign has been conducted in the coastal waters of the southern North Sea during which a variety of marine optical parameters have ben measured. This has enabled the angular distribution factor of spectral radiance or Q factor to be calculated from in situ measurements. The Q factor relates upwelled spectral radiance to upwelled spectral irradiance and its precise determination is of importance in ocean color remote sensing. Previous modeling studies, often based on the optical properties of case I waters, have proposed a value of 5 for Q. However, this study suggest that more turbid coastal waters may approach the Lambertian case of Q close to (pi) .
ABSTRACT In this chapter the ideas of explorers and scientists on transparency and colouring issu... more ABSTRACT In this chapter the ideas of explorers and scientists on transparency and colouring issues of natural waters are sketched over a period between 1600 and 1930, from the time of Sir Francis Bacon to Chandrasekhara Raman. This history features famous scientists as well as various amateurs who were intrigued by these optical phenomena. We also discuss are a number of pieces of interesting equipment that were developed to quantify the intrinsically coupled transparency and colour of the sea. The Secchi disc (to determine water transparency) and the Forel–Ule scale (to classify sea and colour) are two, from the end of the nineteenth century, which have withstood the time. The hidden mechanisms for the colouring of water were only solved at the beginning of the twentieth century. It is argued that this delay was partially caused by the fact that the subject was mostly treated as marginal; also, if pure water distillation techniques had been fully developed earlier, this understanding could have been shifted backwards by decades. This chapter ends with Chandrasekhara Venkata Raman, who proved in 1922 that molecular scattering of light in water, in combination with the absorption of the longer wavelengths, caused the blue colour of the sea. In his Nobel lecture ‘On the colour of the sea’ on December 11, 1930 he explained his findings to the world.
. Ground truth measurements are necessary for the validation of remotely sensed data. Rapid ship ... more . Ground truth measurements are necessary for the validation of remotely sensed data. Rapid ship or aircraft spectral measurements of the upwelling and downwelling (ir)radiance are needed to determine the reflectance of the water column as well, as to intercalibrate with satellite ...
Using an optical multichannel analyzer, 168 downswelling irradiance spectra were obtained in vari... more Using an optical multichannel analyzer, 168 downswelling irradiance spectra were obtained in variable atmospheric solar, and cloud cover conditions, and with solar elevations varying between 30 and 60 deg, to retrieve the total spectra in the visible 400-720 nm range. The accuracy of the retrieval is found to be better than that of the determination of some ground truth parameters
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