2005 Volume 13 Pages 285-288
Spectral measurements of downward irradiance and upward radiance were made in the upper Gulf of Thailand to construct an optical model for ocean color remote sensing in turbid waters. Simultaneously, chlorophyll-a concentration, suspended solid concentration, and absorption coefficients of chlorophyll-a, particulate matter and CDOM were measured. Inorganic suspended solid (ISS), which is high scattering property, was also measured as an ignition loss of suspended solid.“Measured” subsurface reflectance was compared with “estimated” that to evaluate the optical model. The measured subsurface reflectance was calculated from spectral radiation measurements. On the other hand, the estimated reflectance was derived from the optical model with absorption and backward-scattering coefficients of in-water substances. The absorption coefficients were used the measured values. Although the backward-scattering coefficient of phytoplankton was used the equation given from previous study, that of ISS was estimated on the basis of Mie theory using the measurement of its absorption coefficient and size distribution. The estimated reflectance agrees with the measured reflectance in the case of lower ISS concentration, but that is 2 times as high as the measured in the case of higher ISS concentration. This mainly cause is an overestimation of the ISS backward-scattering coefficient. It is necessary to improve the estimation method and to conduct measurements in various ocean conditions.
