Spectral attenuation and backscattering as indicators of average particle size

Area of Science:

• Ocean optics
• Particulate matter characterization
• Marine particle size distribution (PSD)

Background:

• Oceanic particulate beam attenuation and backscattering coefficients are spectrally dependent.
• The spectral slope of beam attenuation has been linked to the particle size distribution (PSD) slope.
• Recent advancements allow spectral backscattering measurements from various platforms, including space.

Purpose of the Study:

• To directly compare field-measured PSD with multispectral beam attenuation and backscattering coefficients.
• To investigate the relationship between spectral optical properties and PSD in a coastal bottom boundary layer.
• To assess the utility of backscattering measurements for inferring PSD shape.

Main Methods:

• Field measurements of particle size distribution (PSD).
• Multispectral measurements of beam attenuation coefficient.
• Multispectral measurements of backscattering coefficient.

Main Results:

• The spectral slope of beam attenuation correlated with average particle size, aligning with theoretical predictions for idealized PSD.
• Spectral backscattering measurements also reflected information about average particle size.
• This held true despite significant deviations of the measured PSD from a spectral power law shape.

Conclusions:

• Spectral beam attenuation is a reliable indicator of average particle size in oceanic environments.
• Spectral backscattering offers valuable information on particle size, even for non-ideal particle size distributions.
• These optical methods can enhance our understanding of marine particle characteristics.