In situ optical variability and relationships in the Santa Barbara Channel: implications for remote sensing

Chang, Grace; Barnard, Andrew H.; McLean, Scott; Egli, Peter J.; Moore, Casey; Zaneveld, J. Ronald V.; Dickey, Tommy D.; Hanson, Al

doi:10.1364/ao.45.003593

Cited by 31 publications

(17 citation statements)

References 25 publications

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“…No significant correlations were found between b bp ( 660 ) (or c p ( 660 )) and a ph (or [ chl ]), indicating that their variability is likely due to the presence of particles other than phytoplankton living cells, as confirmed in section 3.4. The backscattering ratios ( b bp : b p ) at 660 nm were relatively high, varying between 0.009 and 0.037 (CV = 40%), comparable to the values found in some coastal environments [ Twardowski et al , 2001; Boss et al , 2004; Chang et al , 2004; Loisel et al , 2007] where high concentration of inorganic particles are present. The particulate backscattering coefficients at either 532 or 660 nm are well related ( r = 0.83, N = 16, p < 0.05) to the percentage of Emiliania huxleyi cells in the phytoplankton assemblage composition (Table 2).…”

Section: Resultssupporting

confidence: 76%

Environmental conditions and bio-optical signature of a coccolithophorid bloom in the Patagonian shelf

et al. 2011

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[1] In January 2008, a patch of high reflectance detected by ocean color satellite images was sampled during a cruise over the southern Argentinean continental shelf. High calcite concentrations (particulate inorganic carbon (PIC)) found at the patch were associated with dominance of the coccolithophorid Emiliania huxleyi. Relatively low chlorophyll concentrations (0.29 to 1.48 mg m −3 ) were found, but both particulate attenuation (0.27 to 1.15 m −1 ) and backscattering coefficients at 660 nm (0.003 to 0.042 m −1 ) were noticeably high. Particulate inorganic to organic carbon (POC) ratio (PIC:POC) was highly variable (0.02 to 1.1), but mostly high, showing a significant correlation with particulate backscattering coefficient at 660 nm (r = 0.83, p < 0.005). The spectral dependency of the backscattering coefficient followed Gordon et al. (2009). Both the time evolution analyses of normalized water leaving radiance at 551 nm (nLw551) and the high PIC:POC ratios suggested an advanced stage of the coccolithophorid bloom, therefore with high detached coccoliths:cell ratios. Moreover, this was supported by a strong correlation between PIC and both particulate backscattering (r = 0.81, p < 0.005) and particulate beam attenuation coefficient (r = 0.7, p < 0.05). Remote sensing reflectance data were strongly related to particle backscattering and backscattering ratio, but not to absorption. NASA operational algorithms overestimated chlorophyll by a factor of ∼2 and estimated PIC with a relatively high root-mean-square (RMS) error (RMS = 97.9 mg PIC L ) were achieved when we used the original PIC-specific backscattering coefficient (Balch et al., 2005).

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Section: Resultssupporting

confidence: 76%

Environmental conditions and bio-optical signature of a coccolithophorid bloom in the Patagonian shelf

et al. 2011

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“…Inherent optical properties (IOPs), defined as the light absorption, scattering, backscattering and beam attenuation coefficients [ Preisendorfer , 1961], are known to carry a wealth of information that is crucial for coastal zone management: absorption and backscattering coefficients may be directly linked to light regimes [e.g., Kirk , 1984], phytoplankton groups, pigment concentration and size class [ Vaillancourt et al , 2004; Ciotti et al , 2002; Bricaud et al , 2007], water masses [ Morel and Maritorena , 2001; Chang et al , 2006], particle size distribution and composition [ Stedmon et al , 2000; Twardowski et al , 2001; Boss et al , 2004; Coble et al , 2004; Loisel et al , 2007]. Complex and dynamic, coastal regions are important ecological zones but are also vulnerable because of their proximity to the land [ Cohen et al , 1997; Gazeau et al , 2004; Beman et al , 2005].…”

Section: Introductionmentioning

confidence: 99%

Bio‐optical variability of the absorption and scattering properties of the Queensland inshore and reef waters, Australia

et al. 2009

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[1] Inshore estuarine, lagoonal, and reef waters of the Great Barrier Reef (Australia) were sampled between 2002 and 2005 during four dry and one wet tropical seasons. Relationships among three biogeochemical concentrations and five key water optical parameters measured at 129 stations were explored to optically characterize six predefined regions. A significant spatial and seasonal variability in some of the inherent optical properties and concentrations measured was found, reaching over two orders of magnitude in the estuaries. Total suspended solids concentrations ranged from 0.5 to $54 mg L À1 , TChl-a ranged from 0.05 to $9 mg m À3 , color dissolved organic matter (CDOM) ranged from 0.004 to 0.8 m À1 at 440 nm, and the backscattering coefficient ranged from 0.001 to 1.18 m À1 at 555 nm. Our data set was mainly composed of coastal stations (95%), leading to a poor correlation between the three concentrations (R 2 < 0.31). The range of variation in backscattering ratios, power law exponents, and the spectral slopes of CDOM and nonalgal particulate matter is comparable with findings from other coastal and open waters around the world. The empirical relationships between TChl-a and a ph (440) were found to differ from reference models, indicating differences in phytoplankton size structure and populations. High variability in backscattering ratios and associated power law exponents as well as particulate absorption ratios indicated different trends or relationships in particle size and composition between the different regions. Stations close to the reef matrix showed specific characteristics with concentrations typical of oceanic waters but CDOM spectral slopes similar to those of coastal environments.

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“…The comparative analysis identifies a minimum of an error function that is based on the cosine of the angle between the standardized vectors of measured and simulated reflectances, cosθ MS . Cosθ MS is equivalent to the correlation coefficient and measures the similarity in shape between the two reflectance vectors without detecting spectral amplitude differences [Sohn and Rebello, 2002;Chang et al, 2006]. In this way, the algorithm is insensitive to amplitude variations of the measured reflectances, which may be due to the presence of seawater constituents with variable amplitude of the absorption properties but with similar spectral features and/or to inaccurate atmospheric correction of the satellite data [Maselli et al, 2009].…”

Section: Modis Datamentioning

confidence: 99%

“…In particular, Maselli et al [2009] developed a semi-analytical algorithm (SAM_LT) for retrieving the three optical active constituents (CHL, CDOM, SPM) in the Ligurian and North Tyrrhenian Seas. SAM_LT is based on the Spectral Angle Mapping (SAM) technique [Sohn and Rebello, 2002;Chang et al, 2006] and, although initially designed for coastal seawaters, has been recently revisited and applied to open seawaters [Massi et al, 2011]. The primary objective of the current study is to assess the performance of the SAM_LT algorithm in comparison with those of the more renowned algorithms, OC3M and MedOC3.…”

Section: Introductionmentioning

confidence: 99%

Assessment of three algorithms for the operational estimation of [CHL] from MODIS data in the Western Mediterranean Sea

Pieri

Massi

Lazzara

et al. 2015

European Journal of Remote Sensing

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Three algorithms based on MODIS imagery were evaluated for the estimation of Chlorophyll-a concentration ([CHL]) in the Western Mediterranean Sea. The first algorithm (OC3M) is usually applied at global scale, while the second (MedOC3), has been used in the Mediterranean basin. The third algorithm (SAM_LT), specifically developed for the Ligurian and North Tyrrhenian Seas, is here described and applied, in its updated version. The three algorithms were assessed through comparison with 240 sea [CHL] samples collected during the 2002-2011 decade. The results obtained show that OC3M is the most accurate algorithm when used for the entire Western Mediterranean, but is outperformed by SAM_LT in the area where this was originally developed. The impact of different MODIS quality flags on the three algorithms has been finally evaluated, providing guidelines for their operational application in the study area.

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In situ optical variability and relationships in the Santa Barbara Channel: implications for remote sensing

Cited by 31 publications

References 25 publications

Environmental conditions and bio-optical signature of a coccolithophorid bloom in the Patagonian shelf

Environmental conditions and bio-optical signature of a coccolithophorid bloom in the Patagonian shelf

Bio‐optical variability of the absorption and scattering properties of the Queensland inshore and reef waters, Australia

Assessment of three algorithms for the operational estimation of [CHL] from MODIS data in the Western Mediterranean Sea

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