The University of Maine Maine In-situ Sound & Color Lab
School of Marine Sciences

Output of Computations of Optical Properties of Spherical and Nonspherical Particles

Measurements of light scattering from the ocean provide information about its constituents. The inherent optical properties (IOPs) of each particle contribute to the bulk property of the water mass it is immersed in. Information gathered by optical sensors that measure light scattered by marine particles is then translated into information about the size and shape distribution, as well as the refractive index of the particle population. Of particular interest is particle backscattering; not only is it in the direction from which most sensors are located, but the implications of its behavior are not well understood. Mie theory, which is based on the assumption that particles are homogeneous spheres, is a good enough approximation for the smallest of marine particles (Gordon and Du 2001, Voss and Fry 1984) but is likely to be biased for others due to the fact that spheres are an extreme shape with the least surface area to volume ratio of all convex bodies.

This project will contribute a database of the volume scattering function (VSF) of marine-like particles modelled as spheroids in the sizes, shapes, and refractive indices of those found in nature. With increasing particle size or asphericity, exact computational methods become unstable and analytic approximations (Fournier and Evans 1991, Kirk 1976) are used. The database is made available to the public, in particular the ocean optics community, to facilitate in the better understanding of bio-optical measurements that are crucial to environmental monitoring.

  The University of Maine
Orono, Maine 04469
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Website last updated: 18-Mar-14