In Situ Spectroscopy in Ocean and Lake Waters*

Abstract

In situ experimental measurements over the wavelength range 400–700 nm have been made in Crater Lake and in Pacific coastal water to reveal their inherent absorption spectra. The measurements are reported as the ratio of the radiance observed in a horizontal direction underwater to the irradiance falling on the surface of the water and, as such, are independent of the spectral properties of the source of flux as well as those of the detector. The instrument used is discussed briefly and a short theoretical analysis is given to illustrate the effect of changes in absorption and scattering on the ratios obtained.