Spectral dependence of the scattering coefficient in case 1 and case 2 waters.

An approximate linear relationship between the scattering coefficient and the wavelength of light in the visible is found in case 1 and case 2 waters. From this relationship, we estimate scattering at an unknown wavelength from scattering at a single measured wavelength. This approximation is based on measurements in a 1.5-m-thick surface layer collected with an AC9 instrument at 63 stations in the Arabian Sea, northern Gulf of Mexico, and coastal North Carolina. The light-scattering coefficient at 412 nm ranged from 0.2 to 15.1 m(-1) in these waters, and the absorption coefficient at 412 nm ranged from 0.2 to 4.0 m(-1). A separate data set for 100 stations from Oceanside, California, and Chesapeake Bay, Virginia, was used to validate the relationship. Although the Oceanside waters were considerably different from the developmental data set (based on absorption-to-scattering ratios and single-scattering albedos), the average error between modeled and measured scattering values was 6.0% for the entire test data set over all wavelengths (without regard to sign). The slope of the spectral scattering relationship decreases progressively from high-scattering, turbid waters dominated by suspended sediments to lower-scattering, clear waters dominated by phytoplankton.

Remote-sensing technique for determination of the volume absorption coefficient of turbid water.

We use remote-sensing reflectance from particulate R(rs) to determine the volume absorption coefficient a of turbid water in the 400 < lambda < 700-nm spectral region. The calculated and measured values of a(lambda) show good agreement for 0.5 < a < 10 (m(-1)). To determine R(rs) from a particulate, we needed to make corrections for remote-sensing reflectance owing to surface roughness S(rs). We determined the average spectral distribution of S(rs) from the difference in total remote-sensing reflectance measured with and without polarization. The spectral shape of S(rs) showed an excellent fit to theoretical formulas for glare based on Rayleigh and aerosol scattering from the atmosphere.

Effect of suspended particulate and dissolved organic matter on remote sensing of coastal and riverine waters.

We use remote sensing reflectance (RSR) together with the inherent optical properties of suspended particulates to determine the backscattering ratio b(b)/b for coastal waters. We examine the wavelength dependence of b(b)(lambda) and f(lambda)/Q(lambda) and establish the conditions when C(lambda) in RSR(lambda) approximately or = C(lambda)b(b)(lambda)/a(lambda) can be treated as a constant. We found that for case 2 waters, RSR was insensitive to the natural fluctuations in particle-size distributions. The cross-sectional area of the suspended particulate per unit volume, x(g), showed an excellent correlation with the volume scattering coefficient.