Vertical variations in optical properties of the waters in the Yellow Sea and Bohai Sea at seasonal scales and their influencing mechanisms

This research used the profile data measured extensively in the Yellow Sea and Bohai Sea (YSBS) to explain the temporal and spatial distribution characteristics of optical properties and systematically analyzed the influencing mechanisms of the seasonal variations of optical properties in the YSBS in conjunction with synchronously measured hydrological and biogeochemical data in vertical profiles. The main conclusions obtained are as follows: the vertical variations in the optical properties in the YSBS are mainly influenced by the stratification effect, vertical mixing function, and phytoplankton growth process; and the variations of optical properties are dominated by the change of particle characteristics. The backscattering ratio can be used to discriminate particle types as a proxy of particulate bulk refractive index. In the YSBS, for waters with a backscattering ratio of less than 0.012, the variations of optical properties are dominated by the phytoplankton particles. For waters with a backscattering ratio greater than 0.012, the variations of optical properties are dominated by inorganic sediment particles. In addition, for the YSBS, the variations in optical properties of upper surface layer waters can be elucidated well by the vertical variations.