A Review of Protocols for Fiducial Reference Measurements of Downwelling Irradiance for the Validation of Satellite Remote Sensing Data over Water
by
Kevin G. Ruddick 1,*, Kenneth Voss 2
, Andrew C. Banks 3, Emmanuel Boss 4, Alexandre Castagna 5, Robert Frouin 6, Martin Hieronymi 7, Cedric Jamet 8, B. Carol Johnson 9, Joel Kuusk 10, Zhongping Lee 11, Michael Ondrusek 12, Viktor Vabson 10 and Riho Vendt 10
Kevin G. Ruddick 1,*, Kenneth Voss 2, Andrew C. Banks 3, Emmanuel Boss 4, Alexandre Castagna 5, Robert Frouin 6, Martin Hieronymi 7, Cedric Jamet 8, B. Carol Johnson 9, Joel Kuusk 10, Zhongping Lee 11, Michael Ondrusek 12, Viktor Vabson 10 and Riho Vendt 10
1
Royal Belgian Institute of Natural Sciences (RBINS), Operational Directorate Natural Environment, 29 Rue Vautierstraat, 1000 Brussels, Belgium
2
Physics Department, University of Miami, Coral Gables, FL 33124, USA
3
Institute of Oceanography, Hellenic Centre for Marine Research (HCMR), Former US Base Gournes, 71500 Hersonissos, Crete, Greece
4
University of Maine, Orono, ME 04469, USA
5
Protistology and Aquatic Ecology Research Group, Gent University, Krijgslaan 281, 9000 Gent, Belgium
6
Scripps Institution of Oceanography, University of California San Diego, 8810 Shellback Way, La Jolla, CA 92037, USA
7
Institute of Coastal Research, Helmholtz-Zentrum Geesthacht (HZG), Max-Planck-Str. 1, 21502 Geesthacht, Germany
8
Université du Littoral-Côte d’Opale, CNRS, Université de Lille, UMR8187, F62930 Wimereux, France
9
National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA
10
Tartu Observatory, University of Tartu, 61602 Tõravere, Estonia
11
School for the Environment, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA 02125-3393, USA
12
National Oceanic and Atmospheric Administration (NOAA), Center for Weather and Climate Prediction, 5830 University Research Court, College Park, MD 20740, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(15), 1742; https://doi.org/10.3390/rs11151742
Received: 17 June 2019 / Revised: 15 July 2019 / Accepted: 18 July 2019 / Published: 24 July 2019
(This article belongs to the Special Issue Fiducial Reference Measurements for Satellite Ocean Colour)
This paper reviews the state of the art of protocols for the measurement of downwelling irradiance in the context of Fiducial Reference Measurements (FRM) of water reflectance for satellite validation. The measurement of water reflectance requires the measurement of water-leaving radiance and downwelling irradiance just above water. For the latter, there are four generic families of method, using: (1) an above-water upward-pointing irradiance sensor; (2) an above-water downward-pointing radiance sensor and a reflective plaque; (3) a Sun-pointing radiance sensor (sunphotometer); or (4) an underwater upward-pointing irradiance sensor deployed at different depths. Each method—except for the fourth, which is considered obsolete for the measurement of above-water downwelling irradiance—is described generically in the FRM context with reference to the measurement equation, documented implementations, and the intra-method diversity of deployment platform and practice. Ideal measurement conditions are stated, practical recommendations are provided on best practice, and guidelines for estimating the measurement uncertainty are provided for each protocol-related component of the measurement uncertainty budget. The state of the art for the measurement of downwelling irradiance is summarized, future perspectives are outlined, and key debates such as the use of reflectance plaques with calibrated or uncalibrated radiometers are presented. This review is based on the practice and studies of the aquatic optics community and the validation of water reflectance, but is also relevant to land radiation monitoring and the validation of satellite-derived land surface reflectance.
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Keywords:
downwelling irradiance; satellite validation; Fiducial Reference Measurements; water reflectance
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
MDPI and ACS Style
Ruddick, K.G.; Voss, K.; Banks, A.C.; Boss, E.; Castagna, A.; Frouin, R.; Hieronymi, M.; Jamet, C.; Johnson, B.C.; Kuusk, J.; Lee, Z.; Ondrusek, M.; Vabson, V.; Vendt, R. A Review of Protocols for Fiducial Reference Measurements of Downwelling Irradiance for the Validation of Satellite Remote Sensing Data over Water. Remote Sens. 2019, 11, 1742.
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