OCEAN INHERENT OPTICAL PROPERTY ESTIMATION FROM IRRADIANCES

A method is evaluated for estimating the absorption coefficient a and the backscattering coefficient b(b) from measurements of the upward an d downward irradiances E-u(z) and E-d(z). With this method, the reflec tance ratio R(z) and the downward diffuse attenuation coefficient K-d( z) obtained from E-u(z) and E-d(z) are used to estimate the inherent o ptical properties R-infinity and K-infinity that are the asymptotic va lues of R(z) and K-d(z), respectively. For an assumed scattering phase function <(beta)over tilde>, there are unique correlations between th e values of R-infinity and K-infinity and those of a and b(b) that can be derived from the radiative transfer equation. Good estimates of a and the Gordon parameter G = b(b)/(a + b(b)) can be obtained from R-in finity and K-infinity if the true scattering phase function is not gre atly different from the assumed function. The method works best in dee p, homogeneous waters, but can be applied to some cases of stratified waters. To improve performance in shallow waters where bottom effects are important, the deep-and shallow-measurement reflectance models als o are developed. (C) 1997 Optical Society of America.