Spectra of particulate backscattering in natural waters

Area of Science:

• Ocean optics
• Aquatic remote sensing
• Inherent optical properties

Background:

• Understanding inherent optical properties (IOPs) like absorption (a) and backscattering (b(b)) is vital for remote sensing of aquatic ecosystems.
• Phytoplankton pigments and particle size distribution significantly influence IOPs in natural waters.

Purpose of the Study:

• To derive high-resolution spectra of absorption and backscattering coefficients from hyperspectral radiance and irradiance data.
• To identify spectral signatures of phytoplankton pigments and characterize particle backscattering in oligotrophic and mesotrophic waters.

Main Methods:

• Combined hyperspectral downwelling irradiance and upwelling radiance measurements.
• Applied inverse radiative transfer modeling to retrieve IOP spectra.
• Analyzed spectral features of absorption and backscattering coefficients.

Main Results:

• Identified distinct absorption features attributed to Chlorophyll a, b, c, and carotenoids in mesotrophic waters.
• Characterized backscattering as a power-law function of wavelength (b(b) ~ lambda(-n), n=0.4-1.0).
• Observed depression of spectral features in backscattering spectra correlating with strong particle absorption.

Conclusions:

• The inverse radiative transfer method effectively retrieves IOPs, revealing pigment-specific absorption.
• Backscattering is largely spectrally flat, with minor deviations linked to particle absorption.
• The algorithm's accuracy is wavelength-dependent, limited by the omission of Raman scattering.