Variability of the downwelling diffuse attenuation coefficient with consideration of inelastic scattering

In situ time-series measurements of spectral diffuse downwelling irradiance from the Bermuda Testbed Mooring are presented. Averaged diffuse attenuation coefficients of downwelling irradiance, K-d, and their elastic and inelastic components are investigated at seven wavelengths. At shorter wavelengths (<510 nm), K-d is weakly dependent on the solar zenith angle owing to the prevailing scattering effect and therefore can be considered a quasi-inherent optical property. At longer wavelengths (>510 nm), K-d shows a strong dependence on the solar zenith angle. As depth increases, inelastic scattering plays a greater role for the underwater light field at red wavelengths. (C) 2002 Optical Society of America.