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We present hydrographic and optical data collected concurrently from two different platforms, the R/P FLoating Instrument Platform and the R/V Kilo Moana, located about 2 km apart in the Santa Barbara Channel in California. We show that optical variability between the two platforms was due primarily to platform effects, specifically the breakdown of stratification from mixing by the hull of R/P FLIP. Modeled underwater radiance distribution differed by as much as 50% between the two platforms during stratified conditions. We determine that the observed optical variability resulted in up to 57% differences in predicted horizontal visibility of a black target. OCIS codes: 010.7295, 010.4450.

We develop a computationally fast radiative transfer model for simulating the fluctuations of the underwater downwelling irradiance [E.sub.d] at near-surface depths, which occur due to focusing of sunlight by wind-driven surface waves. The model is based on the hybrid matrix operator--Monte Carlo method, which was specifically designed for simulating radiative transfer in a coupled atmosphere--surface--ocean system involving a dynamic ocean surface. In the current version of the model, we use a simplified description of surface waves, which accounts for surface slope statistics, but not surface wave elevation, as a direct source of underwater light fluctuations. We compare the model results with measurements made in the Santa Barbara Channel. The model-simulated and measured time series of [E.sub.d](t) show remarkable similarity. Major features of the probability distribution of instantaneous irradiance, the frequency content of irradiance fluctuations, and the statistical properties of light flashes produced by wave focusing are also generally consistent between the model simulations and measurements for a few near-surface depths and light wavelengths examined. Despite the simplification in the representation of surface waves, this model provides a reasonable first-order approximation to modeling the wave focusing effects at near-surface depths, which require high temporal and spatial resolution (of the order of i ms and 1 mm, respectively) to be adequately resolved. [c] 2010 Optical Society of America OCIS codes: 010.5620, 290.4210, 290.7050, 010.1290, 010.4450.

The hybrid matrix operator, Monte Carlo (HMOMC) method previously reported [Appl. Opt. 47, 1063-1071 (2008)] is improved by neglecting higher-order terms in the coupling of the matrix operators and by introducing a dual grid scheme. The computational efficiency for solving the vector radiative transfer equation in a full 3D coupled atmosphere--surface--ocean system is substantially improved, and, thus, large-scale simulations of the radiance distribution become feasible. The improved method is applied to the computation of the polarized radiance field under realistic surface waves simulated by the power spectral density method. To the authors' best knowledge, this is the first time that the polarized radiance field under a dynamic ocean surface and the underwater image of an object above such an ocean surface have been reported. OCIS codes: 010.5620, 290.4210, 290.7050, 010.1290, 010.4450.

A numerical approach for the calculation of the internal dipole radiation associated with particles of arbitrary morphology is investigated by using the discrete-dipole approximation (DDA) method. The DDA and analytical solutions for the total radiated power and radiation pattern are compared in the case of spherical host particles. It is shown that the DDA can be quite accurate under the condition that m [??] 2, and mkd < 0.5, where m is the refractive index of the host particle, k = 2[pi]/[lambda] is the wavenumber in vacuum, and d is the distance between two adjacent dipoles in the DDA cubic dipole array. Furthermore, the DDA solutions for the dipole radiation patterns associated with nonspherical host particles are compared with their corresponding counterparts obtained from the finite-difference time-domain method. Excellent agreement between the two results is noted. The DDA method is also applied to the computation of the internal dipole radiation associated with simulated nonspherical sporelike particles. The results suggest that the internal dipole radiation patterns contain a great deal of information about the morphology and composition of the host particle. OCIS codes: 350.5610, 290.5860.