Comparison of measured and satellite-derived spectral diffuse attenuation coefficients for the Arabian Sea

An empirical algorithm to estimate spectral average cosine of underwater light field from remote sensing data in coastal oceanic waters

“…The following two facts encouraged us to develop the algorithm for deriving spectral underwater average cosine. One, the algorithm developed earlier (Talaulikar et al 2012) to derive underwater average cosine at 490 nm using R rs (490) provided good results when compared with the other published algorithms of Haltrin and Timofeyeva, and second, R rs (λ), which is defined as the ratio of upwelling radiance to downwelling irradiance just above the sea surface (Eq. 4) is one of the prime optical parameters that is derived from ocean color satellite sensors after applying the appropriate atmospheric correction algorithm.…”

“…However, presently there are no commercial instruments available to obtain this parameter. Some algorithms to derive average cosine have been developed for specific bands or specific wavelengths valid for specific boundary conditions (Berwald et al 1995;Stramska et al 2000;Talaulikar et al 2012) whereas others assume average cosine to be a constant value (Ciotti et al1999;Penta et al 2008); however it was observed to vary spectrally. Hence, assuming a constant value will yield erroneous results in models and related applications for the waters with varying absorption and scattering properties.…”

“…Probable reasons could be due to errors in the inherent optical properties estimated using empirical relationships; remote sensing reflectance derived from the ocean color satellite data and also to the formulation of the simple algorithm based on the value of remote sensing reflectance. To demonstrate the utility value of the algorithm developed by Talaulikar et al 2012, (490) μ μ μ using this algorithm with the NOMAD and IOCCG data sets showed very close match (Talaulikar et al 2012).…”

“…The algorithms of Haltrin and Timofeyeva require inherent optical properties and hence to derive (λ) from ocean color data, it is first required to obtain these optical parameters using empirical algorithms. An empirical algorithm developed by Talaulikar et al (2012) based only on the remote sensing reflectance could be used to derive (490) from the ocean color satellite data. This algorithm performed better than those of Haltrin and Timofeyeva at 490 nm.…”

Empirical algorithm to estimate the average cosine of underwater light field at 490 nm

“…The average cosine derived from the algorithm Mu compared well with those obtained from the simulations and its performance was better compared to the algorithms of Timofeyeva and Haltrin. The error analyses was carried out using the statistical parameters average percentage deviation (APD), mean percentage deviation (MPD), root mean square error (RMSE) and coefficient of determination (R 2 ) (Suresh et al 2011) (Table 1 and Figure 3). …”