scholarly journals Analyzing Satellite Ocean Color Match-Up Protocols Using the Satellite Validation Navy Tool (SAVANT) at MOBY and Two AERONET-OC Sites

2021 ◽  
Vol 13 (14) ◽  
pp. 2673
Author(s):  
Adam Lawson ◽  
Jennifer Bowers ◽  
Sherwin Ladner ◽  
Richard Crout ◽  
Christopher Wood ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Ocean Color ◽  
Visible Spectrum ◽  
Ground Truth ◽  
Naval Research ◽  
Satellite Validation ◽  
The Difference ◽  
Stability And Accuracy ◽  
Satellite Ocean Color

The satellite validation navy tool (SAVANT) was developed by the Naval Research Laboratory to help facilitate the assessment of the stability and accuracy of ocean color satellites, using numerous ground truth (in situ) platforms around the globe and support methods for match-up protocols. The effects of varying spatial constraints with permissive and strict protocols on match-up uncertainty are evaluated, in an attempt to establish an optimal satellite ocean color calibration and validation (cal/val) match-up protocol. This allows users to evaluate the accuracy of ocean color sensors compared to specific ground truth sites that provide continuous data. Various match-up constraints may be adjusted, allowing for varied evaluations of their effects on match-up data. The results include the following: (a) the difference between aerosol robotic network ocean color (AERONET-OC) and marine optical Buoy (MOBY) evaluations; (b) the differences across the visible spectrum for various water types; (c) spatial differences and the size of satellite area chosen for comparison; and (d) temporal differences in optically complex water. The match-up uncertainty analysis was performed using Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) SNPP data at the AERONET-OC sites and the MOBY site. It was found that the more permissive constraint sets allow for a higher number of match-ups and a more comprehensive representation of the conditions, while the restrictive constraints provide better statistical match-ups between in situ and satellite sensors.

scholarly journals Comparison of Above-Water Seabird and TriOS Radiometers along an Atlantic Meridional Transect

2020 ◽  
Vol 12 (10) ◽  
pp. 1669
Author(s):  
Krista Alikas ◽  
Viktor Vabson ◽  
Ilmar Ansko ◽  
Gavin H. Tilstone ◽  
Giorgio Dall’Olmo ◽  
...  
Keyword(s):  
State Of The Art ◽  
Ocean Color ◽  
Percentage Difference ◽  
Wide Range ◽  
Before And After ◽  
Reference Measurements ◽  
Satellite Ocean Color ◽  
Good Agreement

The Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC) project has carried out a range of activities to evaluate and improve the state-of-the-art in ocean color radiometry. This paper described the results from a ship-based intercomparison conducted on the Atlantic Meridional Transect 27 from 23rd September to 5th November 2017. Two different radiometric systems, TriOS-Radiation Measurement Sensor with Enhanced Spectral resolution (RAMSES) and Seabird-Hyperspectral Surface Acquisition System (HyperSAS), were compared and operated side-by-side over a wide range of Atlantic provinces and environmental conditions. Both systems were calibrated for traceability to SI (Système international) units at the same optical laboratory under uniform conditions before and after the field campaign. The in situ results and their accompanying uncertainties were evaluated using the same data handling protocols. The field data revealed variability in the responsivity between TRiOS and Seabird sensors, which is dependent on the ambient environmental and illumination conditions. The straylight effects for individual sensors were mostly within ±3%. A near infra-red (NIR) similarity correction changed the water-leaving reflectance (ρw) and water-leaving radiance (Lw) spectra significantly, bringing also a convergence in outliers. For improving the estimates of in situ uncertainty, it is recommended that additional characterization of radiometers and environmental ancillary measurements are undertaken. In general, the comparison of radiometric systems showed agreement within the evaluated uncertainty limits. Consistency of in situ results with the available Sentinel-3A Ocean and Land Color Instrument (OLCI) data in the range from (400…560) nm was also satisfactory (−8% < Mean Percentage Difference (MPD) < 15%) and showed good agreement in terms of the shape of the spectra and absolute values.

Electroretinographic Determination of Spectral Sensitivity in Albino and Pigmented Brook Trout (Salvelinus fontinalis, Mitchill)

1971 ◽  
Vol 49 (12) ◽  
pp. 1030-1037 ◽  
Author(s):  
H. Kobayashi ◽  
M. A. Ali
Keyword(s):  
Absorption Spectrum ◽  
Spectral Sensitivity ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
Narrow Band ◽  
Visible Spectrum ◽  
The Difference

A technique for recording electroretinograms from the unpunctured eyes in situ of living, anesthetized fish is described. This technique permits the use of the same fish in a number of experiments over a period of weeks, months, or years. Using this technique the spectral sensitivity of dark-adapted (scotopic) and light-adapted (photopic) fish was measured at 13 bands of the visible spectrum. The scotopic curves of albino and pigmented trout thus obtained in the winter have their maxima around 525 nm which differ from that of the absorption spectrum of the scotopic pigment in situ and in vitro of older fish obtained in the summer. The photopic curve of the pigmented fish is a broad one with humps around 425 nm, 545 nm, and 595 nm. The albino's curve has a relatively narrow band with a peak around 630 nm and a shoulder at about 550 nm. The difference between the shapes of the two curves may be ascribed to the increase in the intensity of light of longer wavelengths within the eyeball of the albino, due to reflection from blood vessels and sclera caused by the absence of pigmentation.

An Example Crossover Experiment for Testing New Vicarious Calibration Techniques for Satellite Ocean Color Radiometry

2010 ◽  
Vol 27 (10) ◽  
pp. 1747-1759 ◽  
Author(s):  
Kenneth J. Voss ◽  
Scott McLean ◽  
Marlon Lewis ◽  
Carol Johnson ◽  
Stephanie Flora ◽  
...  
Keyword(s):  
Ocean Color ◽  
Free Fall ◽  
Spectral Variation ◽  
Vicarious Calibration ◽  
Satellite Sensors ◽  
Surface Measurements ◽  
The Difference ◽  
Almost All ◽  
Calibration Techniques ◽  
Satellite Ocean Color

Abstract Vicarious calibration of ocean color satellites involves the use of accurate surface measurements of water-leaving radiance to update and improve the system calibration of ocean color satellite sensors. An experiment was performed to compare a free-fall technique with the established Marine Optical Buoy (MOBY) measurement. It was found in the laboratory that the radiance and irradiance instruments compared well within their estimated uncertainties for various spectral sources. The spectrally averaged differences between the National Institute of Standards and Technology (NIST) values for the sources and the instruments were &lt;2.5% for the radiance sensors and &lt;1.5% for the irradiance sensors. In the field, the sensors measuring the above-surface downwelling irradiance performed nearly as well as they had in the laboratory, with an average difference of &lt;2%. While the water-leaving radiance Lw calculated from each instrument agreed in almost all cases within the combined instrument uncertainties (approximately 7%), there was a relative bias between the two instrument classes/techniques that varied spectrally. The spectrally averaged (400–600 nm) difference between the two instrument classes/techniques was 3.1%. However, the spectral variation resulted in the free-fall instruments being 0.2% lower at 450 nm and 5.9% higher at 550 nm. Based on the analysis of one matchup, the bias in Lw was similar to that observed for Lu(1 m) with both systems, indicating the difference did not come from propagating Lu(1 m) to Lw.

scholarly journals Neural Networks Technique for Filling Gaps in Satellite Measurements: Application to Ocean Color Observations

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Vladimir Krasnopolsky ◽  
Sudhir Nadiga ◽  
Avichal Mehra ◽  
Eric Bayler ◽  
David Behringer
Keyword(s):  
Ocean Color ◽  
Ocean Dynamics ◽  
Upper Ocean ◽  
Satellite Measurements ◽  
Cheap Method ◽  
Sensitivity Studies ◽  
The Impact ◽  
Ocean Observations ◽  
Satellite Ocean Color

A neural network (NN) technique to fill gaps in satellite data is introduced, linking satellite-derived fields of interest with other satellites andin situphysical observations. Satellite-derived “ocean color” (OC) data are used in this study because OC variability is primarily driven by biological processes related and correlated in complex, nonlinear relationships with the physical processes of the upper ocean. Specifically, ocean color chlorophyll-a fields from NOAA’s operational Visible Imaging Infrared Radiometer Suite (VIIRS) are used, as well as NOAA and NASA ocean surface and upper-ocean observations employed—signatures of upper-ocean dynamics. An NN transfer function is trained, using global data for two years (2012 and 2013), and tested on independent data for 2014. To reduce the impact of noise in the data and to calculate a stable NN Jacobian for sensitivity studies, an ensemble of NNs with different weights is constructed and compared with a single NN. The impact of the NN training period on the NN’s generalization ability is evaluated. The NN technique provides an accurate and computationally cheap method for filling in gaps in satellite ocean color observation fields and time series.

scholarly journals In situ autonomous optical radiometry measurements for satellite ocean color validation in the Western Black Sea

2014 ◽  
Vol 11 (6) ◽  
pp. 3003-3034 ◽  
Author(s):  
G. Zibordi ◽  
F. Mélin ◽  
J.-F. Berthon ◽  
M. Talone
Keyword(s):  
Black Sea ◽  
Ocean Color ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
In Situ Data ◽  
Infrared Imager ◽  
Color Data ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Satellite Ocean Color

Abstract. The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A) and the Visible/Infrared Imager/Radiometer Suite (VIIRS), is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the Ocean Color component of the Aerosol Robotic Network (AERONET-OC). The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities with those observed at the Gloria site. Results from the comparison of normalized-water leaving radiance LWN indicate biases of a few percent between satellite derived and in situ data at the center-wavelengths relevant for the determination of chlorophyll a concentration (443–547 nm, or equivalent). Remarkable is the consistency among the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center-wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm) and red (i.e., 667 nm, or equivalent) center-wavelengths, suggesting difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters.

scholarly journals Response to Temperature of a Class of In Situ Hyperspectral Radiometers

2017 ◽  
Vol 34 (8) ◽  
pp. 1795-1805 ◽  
Author(s):  
Giuseppe Zibordi ◽  
Marco Talone ◽  
Lukasz Jankowski
Keyword(s):  
Temperature Coefficient ◽  
Spectral Range ◽  
Ocean Color ◽  
Temperature Coefficients ◽  
The Core ◽  
Photodetector Array ◽  
Color Data ◽  
Response To Temperature ◽  
Satellite Ocean Color

AbstractThe response to temperature of sample hyperspectral radiometers commonly used to support the validation of satellite ocean color data was characterized in the 400–800-nm spectral range. Measurements performed in the 10°–40°C interval at 5°C increments showed mean temperature coefficients varying from −0.04 × 10−2 (°C)−1 at 400 nm to +0.33 × 10−2 (°C)−1 at 800 nm, which are largely explained by the temperature coefficient of the photodetector array constituting the core of the sensor. Overall, the results indicate the possibility of applying temperature corrections with an uncertainty of approximately 0.03 × 10−2 (°C)−1 for the class of hyperspectral radiometers investigated in the study.

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