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...and discussion 4.1. Bidirectionality (f/Q) Coefficients g0 and g1 (Table 2) were calculated from field measurements of u(λ) and rrs(λ) according to Eq. (1) using leastsquares non-linear optimization (=-=Press et al., 1986-=-). Resulting coefficients (g0=0.083, g1=0.074) differed somewhat from those of Gordon et al. (1988) (g0=0.095, g1=0.079) and those suggested by Lee et al. (1999) for coastal waters (g0=0.084, g1=0.17)...

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...l is considered negligible): a λð Þ aφ λð Þ þ ad λð Þ þ ag λð Þ þ aw λð Þ; bb λð Þ bbp λð Þ þ bbw λð Þ: ð3Þ Absorption and backscattering by seawater are well established (Buiteveld et al., 1994; =-=Pope & Fry, 1997-=-; Smith & Baker, 1981), and the dissolved and non-algal absorption are generally modeled with an exponentially decaying function with increasing wavelength. Because of their similarity in spectral sha...

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...na l homepage: www.e lsev ie r .com/ locate / rse Author's personal copy can be modeled as a polynomial function of the spectral backscattering and absorption coefficients (Gordon et al., 1975, 1988; =-=Morel & Prieur, 1977-=-): rrs λð Þ Lu λ;0 −ð Þ Ed λ;0 −ð Þ g0u λð Þ þ g1u λð Þ 2 ; ð1Þ where u λð Þ bb λð Þ a λð Þ þ bb λð Þ : ð2Þ Lu and Ed are the spectral upwelling radiance and downwelling irradiance, respectively...

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...gligible): a λð Þ aφ λð Þ þ ad λð Þ þ ag λð Þ þ aw λð Þ; bb λð Þ bbp λð Þ þ bbw λð Þ: ð3Þ Absorption and backscattering by seawater are well established (Buiteveld et al., 1994; Pope & Fry, 1997; =-=Smith & Baker, 1981-=-), and the dissolved and non-algal absorption are generally modeled with an exponentially decaying function with increasing wavelength. Because of their similarity in spectral shape, absorption by CDO...

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...tion of the IOPs (namely absorption and backscattering coefficients and the volume scattering function, VSF), the solar zenith angle, sensor viewing angles, wind speed, and aerosol optical thickness (=-=Gordon et al., 1988-=-; Lee et al., 1999; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; Morel et al., 2002; Preisendorfer, 1961, 1965). In general, they agree that within the remote sensing domain (i.e. depending on ...

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...t composition associated with changes in speciation, light availability, and nutrient stress can also lead to variability in aφ⁎, particularly in the blue (Soret) phytoplankton absorption band (e.g., =-=Bricaud et al., 1995-=-; Hoepffner & Sathyendranath, 1993). We found no predictable relationship between aφ* and Chl, as commonly found in open ocean waters (Bricaud et al., 1995), nor between aφ* and taxonomic composition ...

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...unction show considerable variability depending on optical water type, particularly in the backward direction which is most relevant for remote sensing (Berthon et al., 2007; Fournier & Forand, 1994; =-=Petzold, 1972-=-). In 2011, Lee et al. (2011) devised an IOP-based correction scheme for the angular effects in water-leaving radiance (Lu above the sea surface, Lw(λ,0+)) which considered multiple solar and viewing ...

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...ely absorption and backscattering coefficients and the volume scattering function, VSF), the solar zenith angle, sensor viewing angles, wind speed, and aerosol optical thickness (Gordon et al., 1988; =-=Lee et al., 1999-=-; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; Morel et al., 2002; Preisendorfer, 1961, 1965). In general, they agree that within the remote sensing domain (i.e. depending on the particular stu...

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...ensing of Environment j ourna l homepage: www.e lsev ie r .com/ locate / rse Author's personal copy can be modeled as a polynomial function of the spectral backscattering and absorption coefficients (=-=Gordon et al., 1975-=-, 1988; Morel & Prieur, 1977): rrs λð Þ Lu λ;0 −ð Þ Ed λ;0 −ð Þ g0u λð Þ þ g1u λð Þ 2 ; ð1Þ where u λð Þ bb λð Þ a λð Þ þ bb λð Þ : ð2Þ Lu and Ed are the spectral upwelling radiance and downwell...

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...ms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; Roesler & Perry, 1995; Wang et al., 2005), GSM01 (Garver & Siegel, 1997; Maritorena & Siegel, 2006; =-=Maritorena et al., 2002-=-), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640 nm (QAA640). Fig. 3 shows that for the principal retrieval parameters apg(λ) and bb(λ) the QAA640 out...

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...dg is the spectral slope parameter and λ0 is a reference wavelength. The particulate backscattering coefficient bbp(λ) is modeled using the power-law form commonly found in SAAs (Carder et al., 1999; =-=Lee et al., 2002-=-; Roesler & Boss, 2002): bbp λð Þ bbp λ0ð Þ λ0λ Y ; ð5Þ where Y describes the spectral shape, despite concerns that the shape of backscattering is not entirely independent of absorption, and anom...

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...hose retrieved using five semi-analytical algorithms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; Roesler & Perry, 1995; Wang et al., 2005), GSM01 (=-=Garver & Siegel, 1997-=-; Maritorena & Siegel, 2006; Maritorena et al., 2002), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640 nm (QAA640). Fig. 3 shows that for the principal ...

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...g λ–λ0ð Þ ð4Þ where Sdg is the spectral slope parameter and λ0 is a reference wavelength. The particulate backscattering coefficient bbp(λ) is modeled using the power-law form commonly found in SAAs (=-=Carder et al., 1999-=-; Lee et al., 2002; Roesler & Boss, 2002): bbp λð Þ bbp λ0ð Þ λ0λ Y ; ð5Þ where Y describes the spectral shape, despite concerns that the shape of backscattering is not entirely independent of ab...

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...nic absorption coefficients (ap(λ), aφ(λ), ad(λ), amin(λ)) were measured in a Cary 3E (Varian Inc.) or U-3010 (Hitachi Inc.) dual-beam spectrophotometer following NASA protocols (Bowers et al., 1996; =-=Fargion & Mueller, 2000-=-; Werdell & Roesler, 2003). Spectrophotometer data and data from WET Labs “ac” instruments which were not in mutual agreement (four stations) were eliminated from the dataset. TSM concentration was de...

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...t, extensive work has shown how f/Q depends on solar zenith angle, viewing angle, aerosol optical thickness of the atmosphere, wind speed, and the magnitudes of the IOPs themselves (Lee et al., 2011; =-=Morel & Gentili, 1991-=-, 1993; Morel & Gentili, 1996; Morel et al., 2002; Park & Ruddick, 2005). The total absorption coefficient can be linearly separated into contributions by seawater (aw) and particulate and dissolved a...

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...s which showed that the spectral dependency of the f/Q ratio is closely tied to the biogeochemical and optical nature of the suspended particle population (Chang et al., 2007; Kostadinov et al., 2007;=-=Morel & Gentili, 1993-=-, 1996; Morel et al., 2002). Models and field observations of the particle phase function show considerable variability depending on optical water type, particularly in the backward direction which is...

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...8, 510, 532, 555, and 650 nm) were compared with those retrieved using five semi-analytical algorithms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; =-=Roesler & Perry, 1995-=-; Wang et al., 2005), GSM01 (Garver & Siegel, 1997; Maritorena & Siegel, 2006; Maritorena et al., 2002), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640...

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...ean color imagery collected over the past three decades from numerous orbital platforms has the potential for providing long-term, synoptic retrievals of bio-optical properties in the world's oceans (=-=McClain, 2009-=-). However, satellite ocean color imagery is generally underutilized or improperly interpreted in coastal and estuarine systems largely because standard approaches for retrieving water column properti...

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...ow f/Q depends on solar zenith angle, viewing angle, aerosol optical thickness of the atmosphere, wind speed, and the magnitudes of the IOPs themselves (Lee et al., 2011; Morel & Gentili, 1991, 1993; =-=Morel & Gentili, 1996-=-; Morel et al., 2002; Park & Ruddick, 2005). The total absorption coefficient can be linearly separated into contributions by seawater (aw) and particulate and dissolved absorption (apg). The latter c...

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... zenith angle, viewing angle, aerosol optical thickness of the atmosphere, wind speed, and the magnitudes of the IOPs themselves (Lee et al., 2011; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; =-=Morel et al., 2002-=-; Park & Ruddick, 2005). The total absorption coefficient can be linearly separated into contributions by seawater (aw) and particulate and dissolved absorption (apg). The latter can be further separa...

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...ies considerably with phytoplankton size and pigment composition. For example, pigment packaging effects associated with larger cell sizes common to estuarine waters decrease aφ⁎ with increasing Chl (=-=Ciotti et al., 2002-=-), while changes in pigment composition associated with changes in speciation, light availability, and nutrient stress can also lead to variability in aφ⁎, particularly in the blue (Soret) phytoplankt...

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...particulate backscattering coefficient in the red is high enough to overcome the strong absorption coefficient of water, leading to a sufficient water leaving radiance signal in the 645 nm band (e.g. =-=Miller & McKee, 2004-=-). While such conditions can be expected in many areas within LIS— particularly during periods of high river flow— it remains unknown how broadly this band can be applied across the region. The histor...

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...ious wavelengths (see Table 1 for definitions). In recent years, many new semi-analytical ocean color algorithms (SAAs) (Arnone et al., 2006) and other inversion methods such as neural networks (e.g. =-=Doerffer & Schiller, 2007-=-; Ioannou et al., 2011) have been developed to include retrievals of IOPs in optically complex coastal and estuarine systems where global empirical approaches often fail. In this study, we evaluate re...

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...he solar zenith angle, sensor viewing angles, wind speed, and aerosol optical thickness (Gordon et al., 1988; Lee et al., 1999; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; Morel et al., 2002; =-=Preisendorfer, 1961-=-, 1965). In general, they agree that within the remote sensing domain (i.e. depending on the particular study, solar zenith angleb=~60, sensor viewing angleb=~40°, aerosol optical thicknessb~0.4, wind...

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...reflectance signature, but this approach yields different spectral locations and numbers of wavebands depending on the optical water types used for optimization (e.g. Lee et al., 2007; Mueller, 1976; =-=Sathyendranath et al., 1993-=-). Fig. 2. Spectral locations (approximate band centers in color; available online) of ocean color bands for the SeaWiFS, MODIS (Aqua and Terra), MERIS, OLCI, S-GLI and VIIRS (NPP and NPOES) sensors (...

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...ed with changes in speciation, light availability, and nutrient stress can also lead to variability in aφ⁎, particularly in the blue (Soret) phytoplankton absorption band (e.g., Bricaud et al., 1995; =-=Hoepffner & Sathyendranath, 1993-=-). We found no predictable relationship between aφ* and Chl, as commonly found in open ocean waters (Bricaud et al., 1995), nor between aφ* and taxonomic composition or particle size distribution. To ...

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...use a regional average value for aφ⁎(0.016±0.010 m2 mg−1 at 440 nm) which is within the range of published values for coastal, productive waters with generally larger cell sizes (Brewin et al., 2011; =-=Mitchell & Kiefer, 1988-=-). The QAA as published does not retrieve Chl, but Chl retrieved by the QAALIS using this approach shows a significant improvement over the standard OC3M algorithm designed for MODIS (r2 increased fro...

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...he particle size distribution, whereby polydispersions of larger particles such as those found in coastal and estuarine waters tend to lead to a weaker spectral dependence in bbp (Babin et al., 2003; =-=Morel & Ahn, 1990-=-), although empirical corroboration remains limited. For retrieving Y from rrs (i.e., step 4 in Table 2 of Lee et al. (2002)), we found that a simple linear fit to rrs(531)/rrs(555) (Table 2, this stu...

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...flectance when chlorophyll concentrations are greater than ~5 mg m−3. When intense phytoplankton blooms or “red tides” are present at the sea surface, the spectral peak can be shifted towards 590 nm (=-=Dierssen et al., 2006-=-; Ryan et al., 2005). The red channels are grouped at the far end of the visible spectrum (Fig. 2) in order to capture the in vivo chlorophyll absorption peak around 676 nm and the chlorophyll fluores...

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...ata: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; Roesler & Perry, 1995; Wang et al., 2005), GSM01 (Garver & Siegel, 1997; Maritorena & Siegel, 2006; Maritorena et al., 2002), and QAA (=-=Lee & Carder, 2004-=-; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640 nm (QAA640). Fig. 3 shows that for the principal retrieval parameters apg(λ) and bb(λ) the QAA640 outperformed others in nearly all...

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...ed channels are grouped at the far end of the visible spectrum (Fig. 2) in order to capture the in vivo chlorophyll absorption peak around 676 nm and the chlorophyll fluorescence signature at 685 nm (=-=Behrenfeld et al., 2009-=-). However, even the fluorescence channels can be largely dominated by scattering or “red-edge reflectance” during intense algal blooms (Dierssen et al., 2006; Gilerson et al., 2008). Band selection h...

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...xonomic groups at each station are shown explicitly. 194 D.A. Aurin, H.M. Dierssen / Remote Sensing of Environment 125 (2012) 181–197 Author's personal copy easy to implement (Bowers & Binding, 2006; =-=Dekker et al., 2001-=-, 2002; Kirk, 1994; Miller & McKee, 2004), but the derived regression coefficients vary widely by region depending on the absorption, particle size distribution, and refractive index properties of the...

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...s of the particle phase function show considerable variability depending on optical water type, particularly in the backward direction which is most relevant for remote sensing (Berthon et al., 2007; =-=Fournier & Forand, 1994-=-; Petzold, 1972). In 2011, Lee et al. (2011) devised an IOP-based correction scheme for the angular effects in water-leaving radiance (Lu above the sea surface, Lw(λ,0+)) which considered multiple sol...

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...OP retrievals), data were arranged in log space prior to calculating performance metrics (Maritorena et al., 2006). In addition, linear regression analysis of the measured and modeled IOPs (Type II, (=-=Laws, 1997-=-)) was evaluated for similarity of the regression slope to 1.0 and the intercept to 0. 3. Algorithm selection and tuning 3.1. Semi-analytical algorithm performance Optical properties measured in LIS (...

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...iculate, and minerogenic absorption coefficients (ap(λ), aφ(λ), ad(λ), amin(λ)) were measured in a Cary 3E (Varian Inc.) or U-3010 (Hitachi Inc.) dual-beam spectrophotometer following NASA protocols (=-=Bowers et al., 1996-=-; Fargion & Mueller, 2000; Werdell & Roesler, 2003). Spectrophotometer data and data from WET Labs “ac” instruments which were not in mutual agreement (four stations) were eliminated from the dataset....

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...he two most prevalent taxonomic groups at each station are shown explicitly. 194 D.A. Aurin, H.M. Dierssen / Remote Sensing of Environment 125 (2012) 181–197 Author's personal copy easy to implement (=-=Bowers & Binding, 2006-=-; Dekker et al., 2001, 2002; Kirk, 1994; Miller & McKee, 2004), but the derived regression coefficients vary widely by region depending on the absorption, particle size distribution, and refractive in...

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...yll concentrations are greater than ~5 mg m−3. When intense phytoplankton blooms or “red tides” are present at the sea surface, the spectral peak can be shifted towards 590 nm (Dierssen et al., 2006; =-=Ryan et al., 2005-=-). The red channels are grouped at the far end of the visible spectrum (Fig. 2) in order to capture the in vivo chlorophyll absorption peak around 676 nm and the chlorophyll fluorescence signature at ...

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...relevant absorption or fluorescence features in this part of the spectrum besides water absorption itself. While the absorption spectrum of seawater is slightly dependent on temperature and salinity (=-=Sullivan et al., 2006-=-), the spectral shape rises abruptly at 600 nm and increases into the near infrared. Because water absorption is so much higher than any other natural constituent of seawater (e.g., phytoplankton, CDO...

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...50 nm) were compared with those retrieved using five semi-analytical algorithms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; Roesler & Perry, 1995; =-=Wang et al., 2005-=-), GSM01 (Garver & Siegel, 1997; Maritorena & Siegel, 2006; Maritorena et al., 2002), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640 nm (QAA640). Fig. ...

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... the spectral slope of bp as described in Aurin et al. (2010). This approach assumed a spectrally independent backscattering ratio and was supported by Mie theory (Ulloa et al., 1994) and field data (=-=Whitmire et al., 2007-=-), although studies have challenged this assumption for natural waters (McKee & Cunningham, 2005; Snyder et al., 2008), and more extensive multi-spectral measurements of bbp in LIS are clearly warrant...

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... of pigments including Chl (Hooker et al., 2005; Van Heukelman & Thomas, 2001). Phytoplankton chemotaxonomic groupings were determined through analysis of HPLC pigment data using CHEMTAX v2 software (=-=Wright & Jeffrey, 2006-=-) in conjunction with pigment inversion ratios determined through field sampling in LIS by the Connecticut Department of Environmental 184 D.A. Aurin, H.M. Dierssen / Remote Sensing of Environment 125...

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...rum, rather than unnecessary, can be extremely useful for remote sensing applications in order to separate the spectral influence of constituent backscattering from absorption on the reflected light (=-=Lee & Carder, 2002-=-). 1.3. Long Island Sound Prior to the 2010 study byAurin et al. (2010), very little research had been conducted in LIS focusing on optical characterization and ocean color remote sensing. A brief sum...

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...ability in the reflectance signature, but this approach yields different spectral locations and numbers of wavebands depending on the optical water types used for optimization (e.g. Lee et al., 2007; =-=Mueller, 1976-=-; Sathyendranath et al., 1993). Fig. 2. Spectral locations (approximate band centers in color; available online) of ocean color bands for the SeaWiFS, MODIS (Aqua and Terra), MERIS, OLCI, S-GLI and VI...

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...optical complexity deriving from riverine delivery of dissolved and sedimentarymaterial. Both the sensors and algorithms used for routine ocean remote sensing are optimized for open ocean conditions (=-=Dierssen, 2010-=-). Improving retrievals of water borne constituents in other environments including near shore and estuarine systems requires optimization of algorithms using regional in situ measurements of optical ...

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...ature at 685 nm (Behrenfeld et al., 2009). However, even the fluorescence channels can be largely dominated by scattering or “red-edge reflectance” during intense algal blooms (Dierssen et al., 2006; =-=Gilerson et al., 2008-=-). Band selection has also been based on identifying the minimum number of bands required to capture the natural variability in the reflectance signature, but this approach yields different spectral l...

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...3), despite an empirical correction to retrievals (aφ(λ)=0.33aφ(λ)) which brings retrievals closer to the 1:1 line. Each phytoplankton taxonomic group has distinctive absorption characteristics (e.g. =-=Johnsen et al., 1994-=-; Roesler Fig. 11. Waveband specific QAALIS retrievals of total absorption (apg) compared with field measurements, and statistical performance metrics for each band. Fig. 10. Waveband specific QAALIS ...

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...ering ratio and was supported by Mie theory (Ulloa et al., 1994) and field data (Whitmire et al., 2007), although studies have challenged this assumption for natural waters (McKee & Cunningham, 2005; =-=Snyder et al., 2008-=-), and more extensive multi-spectral measurements of bbp in LIS are clearly warranted. Y has been shown to be related to the particle size distribution, whereby polydispersions of larger particles suc...

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...ts (ap(λ), aφ(λ), ad(λ), amin(λ)) were measured in a Cary 3E (Varian Inc.) or U-3010 (Hitachi Inc.) dual-beam spectrophotometer following NASA protocols (Bowers et al., 1996; Fargion & Mueller, 2000; =-=Werdell & Roesler, 2003-=-). Spectrophotometer data and data from WET Labs “ac” instruments which were not in mutual agreement (four stations) were eliminated from the dataset. TSM concentration was determined gravimetrically ...

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...ent with previous studies which showed that the spectral dependency of the f/Q ratio is closely tied to the biogeochemical and optical nature of the suspended particle population (Chang et al., 2007; =-=Kostadinov et al., 2007-=-;Morel & Gentili, 1993, 1996; Morel et al., 2002). Models and field observations of the particle phase function show considerable variability depending on optical water type, particularly in the backw...

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...lly the primary retrieval parameter of the QAA. It has been shown elsewhere that this error propagation can lead to large errors in aφ compared with the other retrieval constituents including adg(λ) (=-=Lee et al., 2010-=-), a finding which is confirmed here. Retrievals of bio-optical properties with a spectral reference band at 640 nm showed significant improvement over the standard 555 nm band because total light abs...

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...ization for all sub-regions and/or times of year. Similarly, multiple biooptical water types were found in the optically complex waters of Tokyo Bay and the Santa Barbara Channel (Chang et al., 2007; =-=Feng et al., 2005-=-). In the latter study, it was shown that the nature of bio-optical water types was a function of the particle composition during various times of year, which varied fromminerogenic to phytoplankton d...

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...ng angle, aerosol optical thickness of the atmosphere, wind speed, and the magnitudes of the IOPs themselves (Lee et al., 2011; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; Morel et al., 2002; =-=Park & Ruddick, 2005-=-). The total absorption coefficient can be linearly separated into contributions by seawater (aw) and particulate and dissolved absorption (apg). The latter can be further separated into absorption co...

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...the Case 1 assumption that volume scattering and absorption properties could be estimated from Chl. More recently, modeling studies have refined estimations of f/Q to extend Eq. (1) to Case 2 waters (=-=Gleason et al., 2012-=-; Hlaing et al., 2012; Lee et al., 2011; Park & Ruddick, 2005) by incorporating variability in solar and viewing geometry and allowing estimates of the volume scattering function (and therefore f/Q) t...

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...nstant, but in fact, extensive work has shown how f/Q depends on solar zenith angle, viewing angle, aerosol optical thickness of the atmosphere, wind speed, and the magnitudes of the IOPs themselves (=-=Lee et al., 2011-=-; Morel & Gentili, 1991, 1993; Morel & Gentili, 1996; Morel et al., 2002; Park & Ruddick, 2005). The total absorption coefficient can be linearly separated into contributions by seawater (aw) and part...

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...ally independent backscattering ratio and was supported by Mie theory (Ulloa et al., 1994) and field data (Whitmire et al., 2007), although studies have challenged this assumption for natural waters (=-=McKee & Cunningham, 2005-=-; Snyder et al., 2008), and more extensive multi-spectral measurements of bbp in LIS are clearly warranted. Y has been shown to be related to the particle size distribution, whereby polydispersions of...

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...reement between the light field modeled by numerical radiative transfer approximation given apg(λ,z), bb(λ,z), b(λ,z) (where z is depth) and ancillary observations measured in the field (Hydrolight, (=-=Mobley, 1995-=-)) and the light field measured in situ. To avoid possible measurement errors in our tuning dataset, only stations with optimal optical closure (i.e., rank 1, see Eq. 4 in Aurin et al. (2010))were use...

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...d can be applied across the region. The history of band selection was based in part on the concept of a spectral “hinge point” where waters turn from blue to green with the addition of chlorophyll-a (=-=Gordon & Morel, 1983-=-). The band near 440 nm coincides with the strongest chlorophyll-a absorption peak, while absorption by the phycobiliproteins found in cryptomonads and cyanobacteria is centered near the 490 and 510 n...

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...the highly turbid waters of Taihu Lake in China found that shifting the reference wavelength from 640 nm into the near infrared was instrumental in improving retrievals of the absorption coefficient (=-=Le et al., 2009-=-). 4.3. Spectral shape parameters Y, ζ, and ξ For practical reasons, Y, the spectral slope of in situmeasurements of bbp, was estimated in LIS from the spectral slope of bp as described in Aurin et al...

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...ts of bbp, was estimated in LIS from the spectral slope of bp as described in Aurin et al. (2010). This approach assumed a spectrally independent backscattering ratio and was supported by Mie theory (=-=Ulloa et al., 1994-=-) and field data (Whitmire et al., 2007), although studies have challenged this assumption for natural waters (McKee & Cunningham, 2005; Snyder et al., 2008), and more extensive multi-spectral measure...

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... and field observations of the particle phase function show considerable variability depending on optical water type, particularly in the backward direction which is most relevant for remote sensing (=-=Berthon et al., 2007-=-; Fournier & Forand, 1994; Petzold, 1972). In 2011, Lee et al. (2011) devised an IOP-based correction scheme for the angular effects in water-leaving radiance (Lu above the sea surface, Lw(λ,0+)) whic...

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...erefore necessary to use a regional average value for aφ⁎(0.016±0.010 m2 mg−1 at 440 nm) which is within the range of published values for coastal, productive waters with generally larger cell sizes (=-=Brewin et al., 2011-=-; Mitchell & Kiefer, 1988). The QAA as published does not retrieve Chl, but Chl retrieved by the QAALIS using this approach shows a significant improvement over the standard OC3M algorithm designed fo...

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...e the natural variability in the reflectance signature, but this approach yields different spectral locations and numbers of wavebands depending on the optical water types used for optimization (e.g. =-=Lee et al., 2007-=-; Mueller, 1976; Sathyendranath et al., 1993). Fig. 2. Spectral locations (approximate band centers in color; available online) of ocean color bands for the SeaWiFS, MODIS (Aqua and Terra), MERIS, OLC...

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... end. The Connecticut (CT) River delivers the majority of the fresh water to the estuary, although the Hudson River impacts the optical properties in western LIS through exchanges at the western end (=-=Aurin et al., 2010-=-). Stations sampled for algorithm optimization (dots) were widely distributed across the region. 182 D.A. Aurin, H.M. Dierssen / Remote Sensing of Environment 125 (2012) 181–197 Author's personal copy...

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...ing by dissolved material is considered negligible): a λð Þ aφ λð Þ þ ad λð Þ þ ag λð Þ þ aw λð Þ; bb λð Þ bbp λð Þ þ bbw λð Þ: ð3Þ Absorption and backscattering by seawater are well established (=-=Buiteveld et al., 1994-=-; Pope & Fry, 1997; Smith & Baker, 1981), and the dissolved and non-algal absorption are generally modeled with an exponentially decaying function with increasing wavelength. Because of their similari...

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... algorithm parameterization for all sub-regions and/or times of year. Similarly, multiple biooptical water types were found in the optically complex waters of Tokyo Bay and the Santa Barbara Channel (=-=Chang et al., 2007-=-; Feng et al., 2005). In the latter study, it was shown that the nature of bio-optical water types was a function of the particle composition during various times of year, which varied fromminerogenic...

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...that volume scattering and absorption properties could be estimated from Chl. More recently, modeling studies have refined estimations of f/Q to extend Eq. (1) to Case 2 waters (Gleason et al., 2012; =-=Hlaing et al., 2012-=-; Lee et al., 2011; Park & Ruddick, 2005) by incorporating variability in solar and viewing geometry and allowing estimates of the volume scattering function (and therefore f/Q) to vary somewhat with ...

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... 1 for definitions). In recent years, many new semi-analytical ocean color algorithms (SAAs) (Arnone et al., 2006) and other inversion methods such as neural networks (e.g. Doerffer & Schiller, 2007; =-=Ioannou et al., 2011-=-) have been developed to include retrievals of IOPs in optically complex coastal and estuarine systems where global empirical approaches often fail. In this study, we evaluate remote sensing algorithm...

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...). Fig. 2. Spectral locations (approximate band centers in color; available online) of ocean color bands for the SeaWiFS, MODIS (Aqua and Terra), MERIS, OLCI, S-GLI and VIIRS (NPP and NPOES) sensors (=-=NRC, 2011-=-) overlaid on the median remote sensing reflectance spectrum (black line) and standard deviation (shaded region) for LIS. With the exception of the MERIS and OLCI sensors, a notable gap in coverage ex...

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...gned for ocean color analysis. It has a very broad spectral response (~50 nm) and a low signal to noise ratio (SNR) geared for land-based remote sensing; the on-orbit SNR for the 645 nm band is ~200 (=-=Xiong et al., 2010-=-) versus ~2000 for ocean color bands. This limits the use of this band to only the most turbid coastal waters where the particulate backscattering coefficient in the red is high enough to overcome the...

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...ationships with the remote sensing reflectance, Rrs(λ), or ratios of Rrs at various wavelengths (see Table 1 for definitions). In recent years, many new semi-analytical ocean color algorithms (SAAs) (=-=Arnone et al., 2006-=-) and other inversion methods such as neural networks (e.g. Doerffer & Schiller, 2007; Ioannou et al., 2011) have been developed to include retrievals of IOPs in optically complex coastal and estuarin...

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...and bb at 412, 440, 488, 510, 532, 555, and 650 nm) were compared with those retrieved using five semi-analytical algorithms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (=-=Boss & Roesler, 2006-=-; Roesler & Perry, 1995; Wang et al., 2005), GSM01 (Garver & Siegel, 1997; Maritorena & Siegel, 2006; Maritorena et al., 2002), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to...

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... (Dierssen et al., 2006). High resolution spectral information between 430 and 500 nm, for example, has been used elsewhere to differentiate distinct absorption features of diatoms and cyanobacteria (=-=Chang et al., 2004-=-; Ryan et al., 2005). Determining whether these approaches can be successful in waters like LIS where between 60% and 97% (median 89%) of particulate and dissolved absorption is attributable to adg ra...

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...they are uncommon in winter and spring. The diversity in phytoplankton taxa found in this study agrees with earlier studies conducted in LIS by the Connecticut Department of Environmental Protection (=-=CTDEP, 2005-=-). Unfortunately, within the limited number of rank 1 stations with HPLC measurements (n=18), no discernible patterns were found between the quality of aφ(λ) retrievals and phytoplankton taxonomic gro...

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...liminated from the dataset. TSM concentration was determined gravimetrically at selected stations during summertime cruises in 2005, 2006 and 2011 following the procedures outlined in NASA protocols (=-=Hooker et al., 1995-=-). Hyperspectral (325 nm–1075 nm, 1 nm resolution) surface reflectance measurements were taken above the sea-surface with a Fieldspec radiometer (Analytical Spectral Devices) and processed to remote s...

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...e United States. Comparison to field measurements revealed that the best semi-analytical model for these highly scattering, turbid waters was the quasi-analytical algorithm (Lee & Carder, 2002, 2004; =-=Lee et al., 2006-=-, 2010). The QAA lends itself easily to optimization of its stepwise, component models which can be tuned independently (i.e. unlike training neural networks, spectral matching as in LMI algorithms, o...

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...ely log-normal distribution (i.e., for Chl or waveband independent IOPs, as opposed to TSM and band-specific IOP retrievals), data were arranged in log space prior to calculating performance metrics (=-=Maritorena et al., 2006-=-). In addition, linear regression analysis of the measured and modeled IOPs (Type II, (Laws, 1997)) was evaluated for similarity of the regression slope to 1.0 and the intercept to 0. 3. Algorithm sel...

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...ve semi-analytical algorithms applied to in situ reflectance data: C99 (Carder et al., 1999, 2006), LMI (Boss & Roesler, 2006; Roesler & Perry, 1995; Wang et al., 2005), GSM01 (Garver & Siegel, 1997; =-=Maritorena & Siegel, 2006-=-; Maritorena et al., 2002), and QAA (Lee & Carder, 2004; Lee et al., 2002, 2006, 2010) referenced to 555 nm (QAA555) or 640 nm (QAA640). Fig. 3 shows that for the principal retrieval parameters apg(λ)...

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... slope parameter and λ0 is a reference wavelength. The particulate backscattering coefficient bbp(λ) is modeled using the power-law form commonly found in SAAs (Carder et al., 1999; Lee et al., 2002; =-=Roesler & Boss, 2002-=-): bbp λð Þ bbp λ0ð Þ λ0λ Y ; ð5Þ where Y describes the spectral shape, despite concerns that the shape of backscattering is not entirely independent of absorption, and anomalous dispersion affec...

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... shape of backscattering is not entirely independent of absorption, and anomalous dispersion affects the shape of backscattering throughout the visible, but most notably near the red absorption peak (=-=Zaneveld & Kitchen, 1995-=-). Incorporation of the IOP spectral models (Eqs. (3)–(5)) into the generic form of the remote sensing reflectance model (Eqs. (1) and (2)) yields the formulation of the SAA convenient for remote sens...