Spectral Distribution of Underwater Irradiance. Bulletin of the Faculty of Fisheries Hakkaido University 26(3

The spectral distributions in the sea near Hakodate in Hokkaido are obtain-ed by an irradiance meter with the calibrations of the absolute spectral response and the immersion effect correction. As for the measured results of the downward underwater irradiance, the spectral distribution in the surface layer is asymmetric and the peak energy is observed near 500 mfL. As depth increases, the longer wave light more than 600 mfL decreases rapidly and the peak shifts slowly towards the shorter wave-length. The spectral distribution of the upward irradiance is symmetric even in the surface layer. The peak of energy is observed at a shorter wavelength rather than the downward irradiance. The theoretical downward irradiance is calculated on the basis of Kishino's method. Theoretical results agree well with the measured values at every water depth