COMPARISON OF NEAR-FORWARD LIGHT-SCATTERING ON OCEANIC TURBULENCE ANDPARTICLES

We examine and compare near-forward light scattering that is caused by turbulence and typical particulate assemblages in the ocean. The near -forward scattering by particles was calculated using Mie theory for h omogeneous spheres and particle size distributions representative of n atural assemblages in the ocean. Direct numerical simulations of a pas sive scalar with Prandtl number 7 mixed by homogeneous turbulence were used to represent temperature fluctuations and resulting inhomogeneit ies in the refractive index of water. Light scattering on the simulate d turbulent flow was calculated using the geometrical-optics approxima tion. We found that the smallest temperature scales contribute the mos t to scattering, and that scattering on turbulence typically dominates over scattering on particles for small angles as large as 0.1 degrees . The scattering angle deviation that is due to turbulence for a light beam propagating over a 0.25-m path length in the oceanic water can b e as large as 0.1 degrees. In addition, we carried out a preliminary l aboratory experiment that illustrates the differences in the near-forw ard scattering on refractive-index inhomogeneities and particles. (C) 1998 Optical Society of America.