Neutral lines and model-measurement closure in oceanic polarized light fields

Area of Science:

• Ocean optics and remote sensing
• Polarized light phenomena in marine environments

Background:

• Polarization of light in the ocean offers insights into water constituents.
• Understanding polarization formation is crucial for ocean optics and remote sensing applications.

Purpose of the Study:

• To measure, model, and interpret the degree and angle of linear polarization (DoLP and AoLP) and neutral points/lines in oceanic light fields.
• To revisit open questions on non-principal plane neutral points and resolve ambiguities in Mueller matrix measurements.

Main Methods:

• Utilized an optical closure experiment with PixPol (polarized radiance fisheye camera) and MASCOT (in-water Mueller matrix instrument).
• Employed Layertran, an ocean-atmosphere vectorial Monte Carlo model for simulations.
• Analyzed empirical measurements against model predictions for polarized light fields.

Main Results:

• Achieved good closure between measurements and modeling for DoLP, AoLP, and neutral lines, particularly in red wavelengths (670 nm).
• Observed systematically lower measured DoLP than modeled DoLP in blue/green wavelengths (444 nm, 500 nm), with undetermined causes.
• Demonstrated that non-principal plane neutral points depend on atmospheric light balance and may be influenced by instrument shading (observer effect).

Conclusions:

• The study provides a baseline for polarimetry methods in ocean optics.
• Results validate smooth interpolation of Mueller matrices for scattering angles >150°.
• Highlights potential for exploiting polarized light data from NASA PACE missions (SPEXone, HARP2).