Fig. 1.
(A) The empirical OC4V4 chlorophyll a algorithm used for the SeaWiFS sensor, which has produced the longest record of global Chl, shown with the original spectral reflectance (Rrs) data from which it was derived (17) and lines indicating data within two- to fivefold of the relationship. Different slopes in the model are due to the wavelength switching from the Rrs(443) at low Chl, Rrs(490) at middle Chl, and Rrs(510) at high Chl. The magenta bar illustrates the large variability in data when the relationship has the steepest slope. (B) Average composite SeaWiFS satellite-derived Chl from 1997 to 2009 for the world ocean.