Phase function effects on the retrieval of oceanic high-spectral-resolution lidar

Area of Science:

• Ocean optics
• Lidar remote sensing
• Monte Carlo simulations

Background:

• Oceanic high-spectral-resolution lidar (HSRL) is crucial for remote sensing of marine environments.
• Accurate retrieval of optical properties like backscattering and attenuation is vital for HSRL applications.
• The influence of particle phase functions on multiple scattering effects in HSRL signals is not fully understood.

Purpose of the Study:

• To develop a semianalytic Monte Carlo model for simulating oceanic HSRL signals, incorporating multiple scattering.
• To investigate the impact of various particulate phase functions on HSRL data retrieval.
• To quantify the errors in effective particulate 180° volume scattering function (VSF) and lidar attenuation coefficient due to phase function variations.

Main Methods:

• Developed a semianalytic Monte Carlo model to simulate oceanic HSRL signals with multiple scattering.
• Analyzed the effects of different phase functions (e.g., Fournier and Forand, two-term Henyey-Greenstein, one-term Henyey-Greenstein) on key optical parameters.
• Quantified the relative differences (δ1 and δ2) between effective and true VSF and attenuation coefficients as a function of depth.

Main Results:

• Particulate backward and forward phase functions significantly influence the effective particulate 180° VSF (δ1), with errors increasing with depth.
• The one-term Henyey-Greenstein phase function showed the largest error (~75%) in effective VSF at depth, while Fournier and Forand showed ~17%.
• Forward phase functions strongly correlate with deviations in lidar attenuation coefficient (δ2), with errors up to ~31% for the one-term Henyey-Greenstein phase function at depth.

Conclusions:

• Multiple scattering and uneven backward phase functions cause deviations in the effective 180° VSF, leading to errors in oceanic HSRL retrievals.
• The choice of phase function critically affects the accuracy of retrieved backscattering and attenuation coefficients, especially at greater depths.
• Accurate phase function representation is essential for reliable interpretation of oceanic HSRL data and understanding marine optical properties.