Variability in optical particle backscattering in contrasting bio‐optical oceanic regimes

Abstract

Variability in the optical particle backscattering coefficient (b bp ) is investigated in oceanic waters from two sites, namely the BOUée pour l'acquiSition d'une Série Optique à Long termE site in the northwestern Mediterranean Sea and the Plumes and Blooms stations in the Santa Barbara Channel off Southern California. Data from these two sites span two orders of magnitude in b bp and likely cover typical open ocean values. A significant relationship is found between b bp at wavelengths of 442 and 555 nm and chlorophyll concentration. However the large spread in this relationship makes chlorophyll a poor predictor of b bp . The relationship between b bp and the particulate beam attenuation coefficient at 660 nm is tighter for both sites, indicating covariability of the particle size ranges that determine both coefficients. A detailed study of the seasonal changes of the b bp vs. chlorophyll relationship reveals that this bio-optical relationship might be best described as a succession of distinct regimes with rapid transitions from one to another. The backscattering ratio (b bp ; the ratio of b bp to total particulate scattering, b p ) ranges from about 0.2% to 1.5%, which is similar to previously reported values. The relationship between b bp and chlorophyll was not significant, while values of the backscattering ratio varied spectrally.

A semianalytical ocean color inversion algorithm with explicit water column depth and substrate reflectance parameterization

“…Nearshore optically complex waters of the Great Barrier Reef are often dominated by suspended sediments and colored dissolved organic matter, CDOM [Blondeau-Patissier et al, 2009]. For optically complex waters, previous research has indicated that smaller values of S and c are more suitable for modeling highly absorbing/scattering waters [Antoine et al, 2011;Blondeau-Patissier et al, 2009;Twardowski et al, 2004]. Thus, we conclude that the SWIM algorithm's parameterization requires refinement in order to reduce product failures in the nearshore region.…”

An optical model for deriving the spectral particulate backscattering coefficients in oceanic waters

“…The importance of the particulate backscattering coefficients in ocean colour remote sensing has been discussed and emphasized in the previous studies (Hoge et al, 1996;Loisel and Stramski, 2000;Maritorena et al, 2002;Lee et al, 2002;Boss and Roesler, Wang et al, 2005;2006;Smyth et al, 2006;Pinkerton et al, 2006;Gordon et al, 2009;Antoine et al, 2011;Shanmugam et al, 2011). Though several models are available to retrieve b bp (λ), as the function of chlorophyll concentration or spectral remote-sensing reflectance, there is a lack of models to provide accurate estimates of b bp (λ) over the entire visible wavelengths with any ocean colour sensors such as SeaWiFS, MODIS and MERIS.…”

“…Earlier studies have reported that the b bp values vary from 0.0002 to 0.001 m −1 in clear oligotrophic waters (Antoine et al, 2011;Loisel et al, 2011), and from 0.03 up to 0.3 m −1 in turbid waters (Neukermans et al, 2011;Boss et al, 2009). The present model has the potential to estimate the b bp values in oceanic waters, where these values vary from 0.0003 to 0.011 m −1 (Figs.…”

“…spectral signature and magnitude) in turbid coastal waters (Shanmugam et al, 2011). This prevents our knowledge of b bp and thus interpretation of ocean colour signals (Antoine et al, 2011). In order to obtain more accurate b bp values, new models with better parameterizations are needed to derive b bp features over the entire visible wavelength domain.…”

Intercomparison of Ocean Color Algorithms for Picophytoplankton Carbon in the Ocean

“…Algorithm C equation was derived using the GSM algorithm for obtaining a relationship between the backscattering coefficient and the B. It has been found in situ, that at low B there may be an overestimation of the b bp by using this satellite-derived relationship (Huot et al, 2008;Antoine et al, 2011;Brewin et al, 2012), yet in situ data also have shown overestimation of backscattering by the QAA algorithm (Behrenfeld et al, 2013). It has been found recently, that Raman scattering plays a role in the discrepancy of the retrievals of the backscattering coefficient in very clear waters from satellite (Westberry et al, 2013), causing an overestimation in backscattering.…”