Abstract
The optical volume scattering function (VSF) of seawater is a fundamental property used in the calculation of radiative transfer for applications in the study of the upper-ocean heat balance, the photosynthetic productivity of the ocean, and the chemical transformation of photoreactive compounds. A new instrument to simultaneously measure the VSF in seven directions between 20° to 160°, the attenuation coefficient, and the depth of water is presented. The instrument is self-contained and can be automatically controlled by the depth under water. The self-contained data can be easily downloaded by an ultra-short-wave communication system. A calibration test was performed in the laboratory based on precise estimation of the scattering volume and optical radiometric calibration of the detectors. The measurement error of the VSF measurement instrument has been estimated in the laboratory based on the Mie theory, and the average error is less than 12%. The instrument was used to measure and analyze the variation characteristics of the VSF with angle, depth and water quality in Daya Bay for the first time. From these in situ data, we have found that the phase functions proposed by Fournier-Forand, measured by Petzold in San Diego Harbor and Sokolov in Black Sea do not fit with our measurements in Daya. These discrepancies could manly due to high proportion of suspended calcium carbonate mineral-like particles with high refractive index in Daya Bay.
Highlights
The volume scattering function (VSF) β(ψ), describes the angular distribution of light scattered from an incident unpolarized beam
All of the instruments historically used for measuring the general-angle VSF of the ocean have a complex mechanical structure because their angular deviation is provided by rotating a bulky light source or photodetector unit around the axis of the scattering volume
The volume scattering function (VSF) is an important inherent optical property of water, and all inherent optical properties of water can be derived according to the VSF and the absorption coefficient
Summary
Cai Li 1, Wenxi Cao 1,*, Jing Yu 2, Tiancun Ke 1, Guixin Lu 1, Yuezhong Yang 1 and Chaoying Guo 1. South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou. Received: 29 February 2012; in revised form: March 2012 / Accepted: March 2012 /
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