Time-resolved polarimetry over water waves: relating glints and surface statistics.

The phenomenon of sunglint, well known in satellite remote sensing, lacks a fundamental characterization under controlled laboratory conditions. Exploiting an apparatus specifically assembled for the purpose, we examine the signal collected by a photopolarimeter, pointed at a wavy water surface with measurable statistics and illuminated by a laser source. We also analyze the wave slope distributions, retrieved with an imaging system, and correlate them with the time series of glints.

Effect of particle asphericity on single-scattering parameters: comparison between Platonic solids and spheres.

The single-scattering properties of the Platonic shapes, namely, the tetrahedron, hexahedron, octahedron, dodecahedron, and icosahedron, are investigated by use of the finite-difference time-domain method. These Platonic shapes have different extents of asphericity in terms of the ratios of their volumes (or surface areas) to those of their circumscribed spheres. We present the errors associated with four types of spherical equivalence that are defined on the basis of (a) the particle's geometric dimension (b) equal surface area (A), (c) equal volume (V), and (d) equal-volume-to-surface-area ratio (V/A).

Use of circular cylinders as surrogates for hexagonal pristine ice crystals in scattering calculations at infrared wavelengths.

We investigate the errors associated with the use of circular cylinders as surrogates for hexagonal columns in computing the optical properties of pristine ice crystals at infrared (8-12-microm) wavelengths. The equivalent circular cylinders are specified in terms of volume (V), projected area (A), and volume-to-area ratio that are equal to those of the hexagonal columns. We use the T-matrix method to compute the optical properties of the equivalent circular cylinders.

Inherent and apparent scattering properties of coated or uncoated spheres embedded in an absorbing host medium.

The conventional Lorenz-Mie formalism is extended to the case for a coated sphere embedded in an absorbing medium. The apparent and inherent scattering cross sections of a particle, derived from the far field and near field, respectively, are different if the host medium is absorptive. The effect of absorption within the host medium on the phase-matrix elements associated with polarization depends on the dielectric properties of the scattering particle.

Scattering from nonspherical Chebyshev particles. 3: Variability in angular scattering patterns.

We study shape-induced variability in the scattered intensity from randomly oriented nonspherical particles. Up to 21 different Chebyshev shapes contribute to defining a shape-induced standard deviation about each of the mean nonspherical intensity vs angle curves shown in part 2 of this series. Bands of shape-induced variability (defined as plus and minus one standard deviation) for six size intervals within the size parameter range 1 View Article and Find Full Text PDF

Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media.

We summarize an advanced, thoroughly documented, and quite general purpose discrete ordinate algorithm for time-independent transfer calculations in vertically inhomogeneous, nonisothermal, plane-parallel media. Atmospheric applications ranging from the UV to the radar region of the electromagnetic spectrum are possible. The physical processes included are thermal emission, scattering, absorption, and bidirectional reflection and emission at the lower boundary.

Scattering from nonspherical Chebyshev particles. 2: Means of angular scattering patterns.

The calculated angular scattering properties of over 250 randomly oriented nonspherical Chebyshev particles are examined for the effect of three factors: size; concavity vs convexity; and amount of deformation from a sphere. Both shape and size averaging are performed to reveal general features of the angular scattering not discernible for particular shapes and sizes. Comparisons with a comparably extensive experimental study published by Zerull in 1976 reveal remarkable qualitative similarities, even though Zerull used greatly different shapes from ours.

Forward optical glory.

Forward optical glory effects in Mie scattering are displayed here for the first time to our knowledge. These effects include regular oscillations in Mie efficiency factors and characteristic deviations from zero polarization in near-forward scattering, which are observable for real refractive indices near radical2 and 2. Complex angular momentum theory predicts the period of oscillation correctly and shows the important role played by surface waves with shortcuts through the sphere.

Improved Mie scattering algorithms.

Scattering of electromagnetic radiation from a sphere, so-called Mie scattering, requires calculations that can become lengthy and even impossible for those with limited resources. At the same time, such calculations are required for the widest variety of optical applications, extending from the shortest UV to the longest microwave and radar wavelengths. This paper briefly describes new and thoroughly documented Mie scattering algorithms that result in considerable improvements in speed by employing more efficient formulations and vector structure.