Model calculations of diffuse attenuation coefficient spectra in lake waters.

The reliability of the models elaborated for recreating the spectra of the light attenuation coefficient, Kd,λ, on the basis of its measured values at 1.3 wavelengths was studied. The coefficients of the one-point. (490 nm) model, elaborated earlier by A. Reinart and A. Herlevi, were tested and approved using 43 new spectra of underwater irradiance measured in 1999-2000. A new version (named C-model) allowing recreation of the spectrum of Kd,λ on the basis on its measured values at three wavelengths was elaborated and tested by statistical analysis. The C-model was found to enable to reconstruct the spectra of Kd,λ with high reliability. Both models gave truthful values of Kd,PAR (mean value of Kd,λ in the region 400.700 nm). For the estimation of the reliability of the experimental initial data, the values of Kd,λ derived from in situ measurements by an underwater spectrometer LI-1800 UW and an instrument ac-9 were compared. The results showed that Kd,λ (ac-9) is mostly lower than Kd,λ (LI-1800UW), the differences increasing with wavelength. [ABSTRACT FROM AUTHOR]