Backscattering by very small particles in coastal waters

Abstract

The volume scattering and backscattering by very small particles (VSPs) of sizes <0.2 μ m in four coastal waters in U.S. (Chesapeake Bay, Monterey Bay, Mobile Bay, and the LEO-15 site) were estimated by inverting the measured volume scattering functions (VSFs) at 532 nm. The measured VSFs are consistent with concurrent measurements of total scattering coefficients by the ac-meters and angular scattering at 100, 125, and 150 by the ECO-VSF sensor and at 140 by the HydroScat-6 sensor. The inferred backscattering coefficients by the VSPs correlate strongly with the absorption coefficients measured for the colored dissolved organic matter, indicating that the dissolved portion of particles do scatter light. In the coastal waters that we studied, the backscattering by VSPs dominate over larger particles (of sizes >0.2 μm), accounting for 40-80% of total backscattering at 532 nm, while only account for <5% of total scattering. Key Points: Backscattering by very small particles was inferred from measured VSFs Backscattering by VSPs and absorption by CDOM correlate strongly VSPs account for 40-80% of total backscattering in coastal waters.