Spectral variations of light scattering by marine particles in coastal waters, from visible to near infrared

Field measurements and Mie calculations of the particulate light-scattering coefficient (b(p), in m(-1)) in the near-infrared and visible spectral domains are combined to quantify and model the effect of particulate absorption on the b(p) spectral variations. The case of particles of coastal origin and assumed to follow a Junge-type size distribution is considered. A simple power-law function closely reproduces the near-infrared b(p) spectral variations, with a spectral slope varying in the range 0.1-1.4. In the visible (e.g., 440 nm), particulate absorption effects systematically lead to b(p) values 5-30% lower than values predicted using a power-law function fitted in the near infrared and extrapolated to 440 nm. The respective influences of the particle size distribution and composition are investigated for both mineral and organic particle populations. Finally, an empirical model derived from theoretical calculations closely reproduces the actual b(p) spectral variations from near-infrared to short visible wavelengths, taking into account particulate absorption effects.