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, Kd,and their elastic and inelastic components are investigated at seven wavelengths. At shorter wavelengths (<510 nm), Kd 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), Kd 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.