Global inherent optical properties from SeaWiFS data

The PML IOP model is a fully analytical approach based on simultaneously solving the remote sensing reflectance equation at two neighbouring wavelengths. For the SeaWiFS sensor these wavelengths are 490 and 510 nm. The only empirical information required is the spectral slope in both backscatter and total absorption for determining the primary measurands of total backscatter and total absorption. These were derived using the COLORS dataset and details can be found in Smyth et al. (2006, doi:10.1364/AO.45.008116). The model assumes a spectral shape for the backscatter and uses this information to extrapolate to the other wavelengths. The bio-geochemical parameters of absorption due to phytoplankton and absorption due to yellow substance and detritus are derived in a similar manner, but this time simultaneously solving for the wavelength pair 412 : 443 nm. Again empirical data from the COLORS dataset is used to solve the equations. The surface interface term has been determined using look-up-tables generated from the HYDROLIGHT radiative transfer scheme and a solution is iteratively arrived at. Again, for full details see Smyth et al., (2006). The input data are the SeaWiFS global normalised water leaving radiance at wavelengths 412, 443, 490, 510 and 555 nm. The nominal resolution of the images is 18 km on an equal angle projection