Light Scattering by Marine Particles: Modeling with Non-spherical Shapes
MIAMI UNIV CORAL GABLES FL DEPT OF PHYSICS
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The inherent optical properties IOPs of marine particles are most-often modeled as homogeneous spheres using Mie Theory. Although this approach has been fruitful, the next logical step in modeling marine particles is to abandon the normally-employed spherical approximation and use more realistic approximations to their shape. The advent of computer codes capable of handling more complex shapes, and the increased computational speeds now available, suggest that particle modeling employing simple non-spherical shapes, e.g., disks, rods, etc., could become routine. For example, Gordon and Du 2001 used a two-disk model to try to reproduce the backscattering by coccoliths detached from E. huxleyi in the blue-green region of the spectrum. They found that the gross morphology of the particle e.g., modeling the coccolith as parallel disks as opposed to a single disk of the same diameter and volume was paramount in determining the spectral variation of backscattering. Later Gordon et al. 2009 showed that the resulting spectral variation of the backscattering cross section for the two-disk model agreed with experiment, and that additional fine structure evident in SEM images of coccoliths had only a minor influence on the backscattering. In another study, Clavano et al. 2007 looked at the IOP of spheroids ellipses of revolution as a function of their size and aspect ratio larger major axis divided by smaller major axis using refractive indices in the range found for marine particles. Their results suggest that, when compared to equal volume spheres, shape can be a significant factor in the IOPs, especially backscattering.