Light Scattering by Marine Particles: Modeling with Non-spherical Shapes
Abstract
The long-term scientific goal of my research is to better understand the distribution of phytoplankton in the world's oceans through remote sensing their influence on the optical properties of the water. An associated goal is the understanding of the absorption and backscattering properties of marine particles in terms of the distributions of their size, shape, and composition. The inherent optical properties (IOPs) of marine particles are most-often modeled as homogeneous spheres using Mie Theory. The next logical step in modeling marine particles is to use more realistic approximations to their shape. The work described here represents my research into computation of the IOPs of non-spherical objects. Of particular interest to me was the scattering and absorption of particles showing significant deviation from spheres, e.g., cylinders with large aspect ratios. This gross morphology resembles long chain phytoplankton. My goal was to develop an understanding at a level that would allow the incorporation of shape information into IOP models and in the analysis of IOP data. Of the several computer codes that allow accurate computation of the scattering and absorption properties of individual particles with smooth nonspherical shapes, I employed the discrete-dipole approximation (DDA). I examined randomly oriented finite cylinders with length up to 25 microns and diameters up to 1.5 microns. At this size, an equal volume sphere has a diameter of about 4 microns. I have completed a study of the scattering and backscattering of non-absorbing randomly-oriented cylinders (diameter of 0.5-1.5 microns) as a function of the length and the index of refraction (1.02 to 1.20). The goal was to understand at what aspect ratio the backscattering becomes essentially proportional to the length. The fact that (normalized) IOPs by cylinders with aspect ratios of 3-5 become independent of the aspect ratio can be used to simplify computation of such for analysis of particle scattering.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2011
- Accession Number
- ADA557188
Entities
People
- Howard R. Gordon
Organizations
- University of Miami