Spectral backscattering coefficient in coastal waters

Based on 186 field observations in the Oslo Fjord of irradiance and radiance and 105 laboratory measurements of beam attenuation, this analysis demonstrates that the ratio between the backscattering coefficient b pb and the scattering coefficient b p of the particles is wavelength dependent and not a constant value. The mean values of b pb/b p at the different wavelengths are close to Petzold's 0.017–0.019 from the San Diego Harbor at 515 nm. For all wavelengths and stations (630 observations) the mean value of b pb/b p is 0.020, the standard deviation of the dataset is 0.015, half of the ratios are greater than 0.020, more than 10% are greater 0.030 and about 5% greater than 0.040. The numerical magnitude of these ratios indicates that small particles are the cause of the latter deviations from the ‘Petzold case’. An example from the northern border of the Skagerrak shows a spectral shape of b pb that can be approximated by λ−1.54, λ being the wavelength, while b p is roughly proportional to λ−0.41. The ...