A SPECTRAL MODEL OF THE BEAM ATTENUATION COEFFICIENT IN THE OCEAN AND COASTAL AREAS

A large set (approximately 100 data points at each wavelength) of multispectral beam attenuation, c(lambda), data at nine wavelengths (440, 450, 490, 520, 535, 550, 565, 630, and 670 nm) is used to develop a spectral model of the beam attenuation coefficient. The relationship c(lambda) - cW(lambda) = [c(490 nm) - cW(490 nm)](1.563 - 1.149 x 10(-3) lambda) describes the spectral variation of c(lambda) where cW(lambda) is the pure water beam attenuation and lambda is the wavelength in nm. From a subset of the data a relationship of chloropyll (Chl) to c(490) was found to be c(490) = 0.39 Chl0.57; however there is significant scatter in this relationship. The spectral c model was tested with independent data sets and the average percent difference of the measured to predicted values ranged from 0.4 to 5% for the different spectral bands.