Date of Award

8-2010

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Emmanuel Boss

Second Committee Member

Huijie Xue

Third Committee Member

Andrew Thomas

Abstract

Seawater inherent optical properties (IOPs) are key parameters in a wide range of applications in environmental studies and oceanographic research. In particular, the absorption coefficient (α) is the typical IOP used to obtain the concentration of chlorophyll-α in the water, a critical parameter in biological oceanography studies, and water quality research makes ample use of the backscattering coefficient (bb) as a measure of turbidity. In this theoretical study we test the feasibility of a small, robust in situ instrument capable of obtaining good estimates of both IOPs. The instrument would emit a laser beam into the water and would retrieve the backscattered light intensity as a function of distance from the center of illumination, which contains information on the water optical properties. We use Monte Carlo modeling of light propagation to create an inversion algorithm that would translate the signal from such an instrument into values of α and bb. Our results, based on simulations spanning the entire natural range of seawater IOP combinations, indicate that an 8 cm - diameter instrument would be capable of predicting bb within less than 13% relative difference, and a within less than 54% (for 90% of the inverted a values, the relative errors fall below 29%). Such a compact and relatively simple device could have multiple applications for in situ optical measurements, including α and bb retrievals from instrumentation mounted on autonomous underwater vehicles. Furthermore, the same methodology could be used to develop an out-of-water sensor for much needed long-term in situ measurements of backscattering and absorption.

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