Old techniques, participatory science and smartphones: Measuring the color of water Extend historic Forel-Ule and Secchi depth dataset Start using 'old fashioned' techniques to produce todays info (original) (raw)
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Earth System Monitoring, 2012
measured above the water consisting of photons that have penetrated the water column and been backscattered out through the air-sea interface. It does not include photons reflected off the sea surface, also called sun glint. Definition of the Subject, Relevance, Motivation The oceans cover over 70% of the earth's surface and the life inhabiting the oceans play an important role in shaping the earth's climate. Phytoplankton , the microscopic organisms in the surface ocean, are responsible for half of the photosynthesis on the planet. These organisms at the base of the food web take up light and carbon dioxide and fix carbon into biological structures releasing oxygen. Estimating the amount of microscopic phytoplankton and their associated over the vast expanses of the ocean is extremely challenging from ships. However, as primary productivity phytoplankton take up light for photosynthesis, they change the color of the surface ocean from blue to green. Such shifts in ocean color can be measured from sensors placed high above the sea on satellites or aircraft and is called "ocean color remote sensing ." In open ocean waters, the ocean color is predominantly driven by the phytoplankton concentration and ocean color remote sensing has been used to estimate the amount of chlorophyll , the primary light-absorbing a pigment in all phytoplankton. For the last few decades, satellite data have been used to estimate large-scale patterns of chlorophyll and to model primary productivity across the global ocean from daily to interannual timescales. Such global estimates of chlorophyll and primary productivity have been integrated into climate models and illustrate the important feedbacks between ocean life and global climate processes. In coastal and estuarine systems, ocean color is significantly influenced by other light-absorbing and light-scattering components besides phytoplankton. New approaches have been developed to evaluate the ocean color in relationship to colored dissolved organic matter, suspended sediments, and even to characterize the bathymetry and composition of the seafloor in optically shallow waters. Ocean color measurements are increasingly being used for environmental monitoring of , critical coastal habitats harmful algal blooms (e.g., seagrasses, kelps), processes, oil spills, and a variety of hazards in the coastal zone. eutrophication
RESEARCH NEEDS IN OCEAN COLOR DATA ANALYSES
Sept 1973 NASA/Goddard Space Flight Center Rept X-652-73-261 The success of the effort to extract several subsurface oceanographic parameters from remotely sensed ocean color data will depend to a great extent upon the existence of adequate theoretical models relating the desired oceanographic parameters to the upwelling radiances to be observed.In order to guide the development of these models, and to check their accuracies, a considerable amount of experimental work must be performed. The theoretical and experimental work which will be needed to develop techniques for the quantitative analysis of satellite ocean color data is described.
THE MODERN FOREL-ULE SCALE: A ‘DO-IT-YOURSELF’ COLOUR COMPARATOR FOR WATER MONITORING
The colour comparator Forel-Ule scale has been used to estimate the colour of natural waters since the 19th century, resulting in one of the longest oceanographic data series. This colour index has been proven by previous research to be related to water quality indicators such as chlorophyll and coloured dissolved organic material. The aim of this study was to develop an affordable, 'Do-it-Yourself' colour scale that matched the colours of the original Forel-Ule scale, to be used in water quality monitoring programs by citizens. This scale can be manufactured with high-quality lighting filters and a white frame, an improvement with respect to the materials employed to manufacture the original scale from the 19th century, which required the mixing of noxious chemicals. The colours of the new scale were matched to the original colours using instrumental and visual measurements carried out under controlled lighting conditions, following the standard measurement protocols for colour. Moreover, the colours of the scale are expressed in Munsell notations, a standard colour system already successfully used in water quality monitoring. With the creation of this Modern Forel-Ule scale, as a 'Do-it-yourself' kit, the authors foresee a possible use of the Forel-Ule number as a water quality index that could be estimated by means of participatory science and used by environmental agencies in monitoring programs.
Special Issue on Remote Sensing of Ocean Color: Theory and Applications
Sensors, 2020
The editorial team are delighted to present this Special Issue of Sensors focused on Remote Sensing of Ocean Color: Theory and Applications. We believe that this is a timely opportunity to showcase current developments across a broad range of topics in ocean color remote sensing (OCRS). Although the field is well-established, in this Special Issue we are able to highlight advances in the applications of the technology, our understanding of the underpinning science, and its relevance in the context of monitoring climate change and engaging public participation.
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...
Advances in radiometry for ocean color
SPIE Proceedings, 2003
Organic materials in the oceans have spectral signatures based on their light-scattering properties. These optical properties are related to bio-physical and biochemical data products such as the concentration of phytoplankton chlorophyll-a through bio-optical algorithms. A primary quantity of interest in ocean color research is the water-leaving spectral radiance L w (λ), often normalized by the incident solar flux. For quantitative studies of the ocean, derivation of the relationship between the optical properties and physically meaningful data products is critical. There have been a number of recent advances in radiometry at the National Institute of Standards and Technology that directly impact the uncertainties achievable in ocean-color research. These advances include a new U.S. national irradiance scale; a new laser-based facility for irradiance and radiance responsivity calibrations; and a novel tunable, solid-state source for calibration and bio-optical algorithm validation. These advances, their relevance to measurements of ocean color, and their effects on radiometrically derived ocean-color data products such as chlorophyll-a are discussed.
1994
Beginning with the upcoming launch of the Sea, viewing Wide Field-of-view Sensor (SeaWiFS), there should be almost continuous measurements of ocean color for nearly 20 years if all of the presently planned national and international missions are implemented. This data set will present a unique opportunity to understand the coupling of physical and biological processes in the world ocean. The presence of multiple ocean color sensors will allow the eventual development of an ocean color observing system that is both cost effective and scientifically based. This report discusses the issues involved and makes recommendations intended to ensure the maximum scientific return from this unique set of planned ocean color missions. An Executive Summary is included with this document which briefly discusses the primary issues and suggested actions to be considered. 1. INTRODUCTION The development of a 20-year time series of ocean color measurements from satellites starting with the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), presents many scientific opportunities to study long-term variability of biological processes in the upper ocean. These studies will range from the response of the upper ocean ecosystem to global climate change to the management of coastal zone resources. There axe several challenges that must be overcome before these studies can be done. These include: crosscalibration and validation of the different sensors which will be launched by the National Aeronautics and Space Administration (NASA), the National Space Development Agency (NASDA) of Japan, and the European Space Agency (ESA); initiation of a program to ensure comprehensive, coordinated observation and modeling plans; and consistency of data processing and data access. The presence of multiple ocean color sensors will allow the eventual development of an ocean color observing system that is both cost-effective and scientifically based. This report discusses these subjects and makes recommendations to ensure the maximum scientific return from this unique set of planned ocean color missions. The Executive Summary (Section 2), encapsulates the primary points made in this document. The remaining content is an in-depth discussion of these subjects and concerns.
Journal of Great Lakes Research, 1997
Utilizing a bio-optical model previously developed for Lake Ontario, the responsiveness of chromaticity coordinates (X, Y, Z), dominant wavelength (Adorn)' and associated spectral purity (p) to the abundance of color-producing agents (CPA) residing within the Lake Ladoga water column was determined. CPA considered were phytoplankton (chi), suspended minerals (sm), and dissolved organic carbon (doc). Waters that contain simultaneously low concentrations of chi, sm, and doc are shown to appear blue to turquoise in color (472-500 nm). Highly turbid waters (i.e., waters containing high concentrations of chl and/or sm) with low concentrations of doc are shown to display colors ranging from green to brown (> 500 nm). Waters with large concentrations of doc, irrespective of turbidity, are shown to be invariably brownish (560-570 nm). With increasing CPA content, X, Y, and Z (and, consequently, Adorn) asymptotically approach constant limit values. An "end-point" dominant wavelength at about 572 nm appears to be intrinsically characteristic of all natural waters. It is shown that when one or more CPA exceeds a critical concentration, the spectral purity p asymptotically approaches values in the range 0.35 to 0.45 for all waters (exceptive of those containing solely chi in the restricted concentration range ::;; 0.5 Ilg/L). Optical distinctiveness, particularly with respect to indigenous doc, of natural waters, while impacting the spectral purity of the "end-point" radiometric color, does not produce a comparable impact on the "end-point" color itself. This work reinforces the restrictive application of chromaticity analyses to the remote sensing of binary aquatic systems comprised of water plus one CPA. It also illustrates that neither panchromatic nor two-channel ratio images can provide unambiguous inference of water quality parameters. Correspondence between radiometric water color descriptors (X, Y, Z, Adorn' and p) and water color scales traditionally used in limnology is established, illustrating that the plat-Radiometric Color ofInland Water inum-cobalt scale would be most appropriate for assessing waters that were radiometrically yellow, provided that the yellow hue were not invariably attributed to doc.