Abstract:

The volume scattering function (VSF, \beta \left(\theta ,\lambda \right)), the absorption coefficient a\left(\lambda \right), and attenuation coefficient c\left(\lambda \right) are the basic parameters of the inherent optical properties of seawater, based on the above parameters, all the inherent and apparent characteristic parameters of the seawater can be further deduced, and the important information data for the basic and front-end research on the primary productivity of the ocean and the global carbon cycle, as well as the military-civilian integration fields application such as the development of the water color remote sensing, the water environment monitoring and disaster early warning, the underwater light field distribution, target tracking, and the photovoltaic power generation will be supported. Limited by the strong directionality of VSF, its measurement technology is difficult and immature. In this paper, with the goal of high-frequency profile measurement of high-angle resolution multi-angle VSF and attenuation coefficient of seawater, a multiangle volume scattering function and attenuation coefficient meter (VSAM) that can simultaneously measure 17 angular VSFs, the attenuation coefficient, the profile depth and temperature information has been described, the measurement angle range of VSF is 10° ~ 170° with the interval of 10°, while the theoretical measurement frequency and deepest profile depth are 20 Hz and 200 m, respectively. With VSAM, the distribution of optical parameters of Sanya Bay and Yazhou Bay has been investigated and studied, and on the whole, the VSFs and attenuation coefficient of Yazhou Bay and Sanya Bay have large changes in horizontal, vertical and angle (for VSFs). The minimum and maximum of VSFs in 120° and 10°, respectively, and the maximum is two or more orders of magnitude larger than the minimum. The attenuation and VSFs show a decreasing trend from west (the Yazhou Bay) to east (the Sanya Bay) in the same water layer and an increasing trend from surface to underwater deeper in the profile at the same station. Combined with the results of water turbidity and chlorophyll concentration profile results measured during the same period, it is found that turbidity is the dominant contribution of the VSFs and attenuation coefficient of the Yazhou Bay, and it also has a good linear correlation with c_{\text{p}}\left(650\right) and {\beta }_{\text{p}}\left(90°,650\right) in these two bays. The attenuation coefficients and VSFs measured by VSAM are in good agreement with the attenuation coefficient measured by Viper (www.trios.de) and the VSFs by ECO-VSF3 (www.seabird.com) in the same stations and water layer during the same period.

Key words: volume scattering function, attenuation coefficient, profile measurement, Sanya Bay, Yazhou Bay