Measurement of Turbidity Distribution in the Interior Part of the Ariake Sea using Landsat-5 TM Data

摘要

The purpose of this study is to establish a method using Landsat-5 TM data for the measurement of the turbidity distribution in the interior part of the Ariake Sea, which has great influences on the environment, ecosystem and marine products. The relationship between the turbidity and spectrum of the sea area, the properties of path radiance in TM data, and the procedures for atmospheric correction and measurement of turbidity distribution were discussed on the basis of turbidity and spectrum which were obtained from in situ measurement, and Landsat-5 TM data. The results indicated that the spectral radiance just above the sea-surface" in the wavelength range from 0.4 mu m to 0.85 mu m was closely related to the turbidity, but that beyond the wavelength of 0.95 mu m it was almost zero, and the path radiance, which occupied about 90% to 70% of the radiance of TM Bands 1 to 4, was dependent on the law of about —3th power of wavelength. A reasonable and simple method of atmospheric correction for TMdata by using the radiance of TM Band 5 which seemed to be equivalent to the path radiance over the sea area and the dependence of path radiance on the wavelength was also presented. Moreover, the turbidity distributions in the study site were exactly measured by the regression equation between the turbidity and the ratio of radiances of TM Band 3 and Band 2 which were corrected for the atmospheric effects.