The variation of the polarized downwelling radiance distribution with depth in the coastal and clear ocean

Abstract

[1] The spectral polarized radiance distribution provides the most complete description of the light field that can be measured. However, this is a very difficult parameter to measure, particularly near the surface, because of its large dynamic range, changes in the skylight illumination, and waves at the air-sea interface. To measure the Stokes vector of the downwelling light field, which contains the polarization information, requires the combination of four images acquired simultaneously. To achieve this, we used the downwelling polarized radiance distribution camera system (DPOL) during the Radiance in a Dynamic Ocean (RaDyO) program Santa Barbara Channel and Hawaiian experiments. DPOL consists of four fisheye lenses and a spectral filter changer that allow us to capture the downwelling hemisphere of the polarized radiance distribution at seven wavelengths. Our measurements show that very near the surface, for clear sky conditions, the dominant source of polarization is the refracted sky light. As one progresses in the water column the polarization due to light scattering by the water increases and polarization due to light scattering in the water becomes dominant.Citation: Bhandari, P., K. J. Voss, L. Logan, and M. Twardowski (2011), The variation of the polarized downwelling radiance distribution with depth in the coastal and clear ocean,

A method to calculate Stokes parameters and angle of polarization of skylight from polarized CIMEL sun/sky radiometers

“…In this frame, the meridian plane is defined as a reference plane. The corresponding coordinate system l-r-z is the right-handed Cartesian coordinate system with l-and r-axes parallel and perpendicular to the reference plane, respectively, and light propagating along the z ¼ r  l direction [32]. For solar principal plane observations, the principal plane corresponds to the meridian plane.…”

“…By definition, I and DoLP are independent of the reference plane, while the Stokes parameters Q, U, and the angle of polarization vary with definition of the reference plane. Although the reference plane can be arbitrarily chosen through the direction of light propagation, when considering polarization due to a single scattering process, the scattering plane which contains the directions of propagation of the incident and scattered light is usually chosen as a reference; and when considering polarization due to multiple scattering processes in the atmosphere, the meridian plane that contains the view and zenith directions is normally chosen as a reference [25,[31][32][33]. In order to compare with vector radiative transfer model simulations and other polarization measurements, the coordinate system based on the sky frame is adopted in this study to describe the Stokes parameters.…”

“…Transformation of the original reference coordinate system l 0 -r 0 -z 0 to the new reference coordinate system l-r-z requires a rotation of l 0 -and r 0 -axes by the counterclockwise rotation angle α [32]. The rotation of coordinate system can be expressed as [22] …”

The relationship between upwelling underwater polarization and attenuation/absorption ratio

“…Light exhibits, as a result of scattering, some degree of polarization (DoP) in different directions, and this polarization is directly related to the source of the radiation and to the properties of the scatterers. Thus, the polarization state of light carries information about the AOS that can be utilized for remote sensing [2,3] of microphysical and optical properties of particulates including the oceanic hydrosols [4][5][6][7].…”

Polarization Patterns of Transmitted Celestial Light under Wavy Water Surfaces

“…Waterman first measured underwater polarization; subsequently, there are many measurements of linear-polarized light transmitted into water surface [28,31,[52][53][54][55][56][57].…”