Sensitivity analysis of volume scattering phase functions

Area of Science:

• Ocean optics
• Radiative transfer theory
• Inherent and apparent optical properties

Background:

• Accurate volume scattering phase functions are essential for solving the radiative transfer equation and linking inherent optical properties (IOPs) to apparent optical properties (AOPs).
• Phase function measurements are challenging, leading to frequent approximations in radiative transfer models.
• Understanding these approximations' impact is vital for accurate remote sensing of aquatic environments.

Purpose of the Study:

• To investigate the sensitivity of derived AOPs to phase function parameterization.
• To compare measured and modeled AOPs and phase functions in Monterey Bay during an extreme algal bloom.
• To evaluate the performance of different VSF measurement and correction methods.

Main Methods:

• In situ measurements of absorption and attenuation coefficients.
• Two sets of volume scattering function (VSF) measurements at multiple wavelengths and angles.
• Comparison of Hydrolight model outputs with direct measurements.
• Evaluation of manufacturer-supplied versus newly published VSF correction methods.

Main Results:

• Common phase function parameterizations in radiative transfer models consistently overestimated remote-sensing reflectance.
• VSF data processed with manufacturer corrections showed significant reflectance overestimation.
• Newly published corrections substantially improved modeled reflectance accuracy.
• Phase functions derived from multi-angle, multi-wavelength VSF data yielded comparable results to commercial instruments.

Conclusions:

• Phase function parameterization significantly impacts AOP accuracy in radiative transfer models.
• Careful selection of VSF measurement and correction methods is critical for reliable ocean optical modeling.
• This study provides valuable insights for coastal waters experiencing extreme algal blooms.