Mie Theory Simulation and Empirical Analysis of Mass-Specific Backscattering Properties of Suspended Particles in the Yellow and East China Seas

The mass-specific backscattering coefficient (b(bp)*) of suspended particles is mainly affected by their composition and sizes. Studying the variation characteristics of b(bp)* is of great significance to revealing the types and temporal and spatial distribution of such particles in waters and improving the quantitative accuracy of ocean color remote sensing. In this paper, the Mie theory is applied to calculate the b(bp)* of various common algae and inorganic mineral particles in seawater with different particle size distributions, relative refractive indexes, and apparent densities by simulation. It is found that the average b(bp)* of inorganic mineral particles is about twice that of algae particles when their particle size distribution slop. is the same. When xi is 4.0, the b(bp)* of inorganic mineral particles and algae particles at 532 nm are (9.12 +/- 3.18) x 10(-3) m(2).g(-1) and (4.09 +/- 0.48) x 10(-3) m(2).g(-1) respectively. The lower b(bp)* value of algae particles can be explained by the lower real part of their refractive index. Research results of the measured data on the Yellow and East China Seas show that the spatial variability of b(bp)* is lower than that of the backscattering coefficient. When the mass concentration of inorganic particles is dominant in the total particles, the average b(bp)* (532) is 8.46 x 10(-3) m(2).g(-1), which is 2.3 times that, 3.63 x 10(-3) m(2).g(-1) to be specific, when organic particles dominate. The measured b(bp)* decreases in the form of power-law function as the mass concentration proportion of organic particles increases. In view of the simulation results, it is concluded that the variation range of the particle size distribution slope xi of particles in the study waters is 3.6-4.2. In offshore waters dominated by organic particles, xi is about 3.9. In the vicinity of the Yangtze River Estuary, the b(bp)* of the suspended particles varies greatly under the influence of the change in the particle size distribution.