Deriving inherent optical properties from water color: a multiband quasi-analytical algorithm for optically deep waters

Abstract

For open ocean and coastal waters, a multiband quasi-analytical algorithm is developed to retrieve absorption and backscattering coefficients, as well as absorption coefficients of phytoplankton pigments and gelbstoff. This algorithm is based on remote-sensing reflectance models derived from the radiative transfer equation, and values of total absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. In the calculation of total absorption coefficient, no spectral models for pigment and gelbstoff absorption coefficients are used. Actually those absorption coefficients are spectrally decomposed from the derived total absorption coefficient in a separate calculation. The algorithm is easy to understand and simple to implement. It can be applied to data from past and current satellite sensors, as well as to data from hyperspectral sensors. There are only limited empirical relationships involved in the algorithm, and they are for less important properties, which implies that the concept and details of the algorithm could be applied to many data for oceanic observations. The algorithm is applied to simulated data and field data, both non-case1, to test its performance, and the results are quite promising. More independent tests with field-measured data are desired to validate and improve this algorithm.

An assessment of phytoplankton primary productivity in the Arctic Ocean from satellite ocean color/in situ chlorophyll‐a based models

“…Twelve models required satellite products (see Table 3) other than surface chlorophyll and PAR, such as remote sensing reflectance ( Rrs ) at 6 bands (412, 443, 490, 510, 555, and 670 nm from SeaWiFS, and 412, 443, 488, 531, 555, and 667 from MODIS‐Aqua), phytoplankton absorption coefficient ( aph ) derived by the generalized inherent optical property ( GIOP ) algorithm [ Werdell et al ., 2013] at 5 bands (412, 443, 490, 510, and 555 nm from SeaWiFS, and 412, 443, 488, 531, and 547 from MODIS‐Aqua), quasi‐analytical algorithm ( QAA ) total absorption coefficient at 443nm ( a443 ) [ Lee et al ., 2002], GIOP particulate backscattering coefficient at 443 nm ( bbp443 ), and the Lee euphotic depth product ( Z eu_lee ) [ Lee et al ., 2007]. Like satellite chlorophyll and PAR, similar procedures were performed to extract values at the satellite matchup stations using the level‐3, 9 km, 8 day average imagery from SeaWiFS (N=13 from November 1997 to June 2002) and MODIS‐Aqua (N=72 from July 2002 to October 2011).…”

“…[2013] to define the vertical shape of the chlorophyll profile. Model 3 used satellite‐derived reflectance values and the QAA [ Lee et al ., 2002] to compute an independent estimate of the absorption by chromophoric dissolved organic matter that substitutes the contribution foreseen by the Case‐1 water model in the standard model.…”

“…All models assume vertically homogeneous chlorophyll profiles and use Rrs to estimate spectral diffuse attenuation coefficient of downward irradiance (K d ) applying the QAA [ Lee et al ., 2002, 2005]. Model 12 and 13 based on ${\mathrm{normalP}}_{\text{max}}^{\mathrm{normalB}}$ as Bélanger et al .…”

Modelling ocean-colour-derived chlorophyll <i>a</i>

“…We note that Gregg and Rousseaux (2017) make a similar choice of a constant Q. Secondly we convert to above-surface remotely sensed reflectance using the formula of Lee et al (2002):…”

Developments in Earth observation for the assessment and monitoring of inland, transitional, coastal and shelf-sea waters

“…Several inversion techniques (e.g., spectral optimization, linear and nonlinear matrix inversion) have been developed for retrieve IOPs and to relate these to in-water biogeochemical properties (Hoge & Lyon, 1996;Garver & Siegel, 1997;Lee et al, 1999;Carder et al, 1999;Lee et al, 2002;Maritonema et al, 2002;Heege & Fisher, 2004;Smyth et al, 2006;Santini et al, 2010;Giardino et al, 2012;Werdell et al, 2013). Although, these models are physic-based many rely on empirical assumptions, while others require knowledge of the specific IOPs (SIOPs; i.e., absorption or scattering per unit mass) (Brando & Dekker, 2003).…”