The relationship between the average cosine of the underwater light field and the inherent optical properties of the ocean

A clear understanding of the processes and associated variability which underlie the interaction of the light energy from the sun with ocean waters is crucial to monitoring perturbations to our planet, particularly as the earth becomes more populated and more industrialized. The average cosine of the underwater light field provides a simple characterization of the angular radiance distribution in the ocean and is important in models of primary productivity and in the interpretation of remotely sensed reflectance. This thesis provides conceptual and quantitative understanding of how the processes of absorption and scattering in the ocean affect the average cosine of the underwater light field.; The individual contributions of absorption and scattering to the rate of change of the average cosine are calculated according to the linearization approach. The most important result of this analysis is that scattering, rather than absorption, plays the more significant role in the changes of the average cosine with depth in natural waters. The Lamina Model for the downwelling average cosine is based on the radiative transfer equation for a thin optical layer. This model is superior to earlier models since it provides insight into the processes that determine the underwater radiance distribution.; Investigation of the asymptotic light field in the presence of Raman scattering shows that strong vertical gradients and a quasi-asymptotic field may be features of the depth profiles of the average cosine. Between chlorophyll concentrations 0.05 to 5 mg {dollar}rm msp{lcub}-3{rcub},{dollar} Raman scattering has negligible effects on the light field in the blue wavelengths and large effects in the red wavelengths. Green wavelengths will be affected by Raman scattering if they are longer than the transition which is 500 nm for Chl = 0.05 mg {dollar}rm msp{lcub}-3{rcub}{dollar} and increases to 590 nm for Chl = 5 mg {dollar}rm msp{lcub}-3{rcub}.{dollar} A linear relationship is found between the ratios {dollar}{lcub}barmusb{lcub}infty{rcub} *(lambda)overbar musb{lcub}infty{rcub}(lambda){rcub}{dollar} and {dollar}{lcub}rm Ksb{lcub}infty{rcub}(lambdaprime)over a(lambda){rcub}.{dollar} This thesis concludes with the Packet Model which is both a conceptual and mathematical model of Raman scattered light in the asymptotic field.