Chaoying Guo

An Instrument for In Situ Measuring the Volume Scattering Function of Water: Design, Calibration and Primary Experiments

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.

Optical systems for applications in ocean color remote sensing and interdisciplinary study

A shipboard ocean optical profiling system (SOOPS) has been developed to meet the needs of ocean color remote sensing. This system is an integrated one that provide measurements of optical properies of seawater. Specifications of SOOPS are described. Shading errors are modeled by Monte Carlo simulation, the field experimental data and some optical properties derived from these data are described and analyzed. Also presented in this paper is an optical buoy system underdeveloped, which can provide time series observations of both inherent optical properties and apparent optical properties of sea water. This system consistents of two buoys, master buoy and slave bouy. Several optical instruments are mouted on the buoys or on the mooring cable of the buoys to provide optical measurements at depths up to 70m. Self shading of the buoy has been simulated via Monte Carlo method. Effective anti-biofouling techniques are used for protecting biofouling on the optical window. Bluetooth radio is used for the communication between the master buoy and the slave buoy. An Inmarsat satellite telemetry system is used to transmit data daily. These optical systems are useful for both verification of ocean color satellite data and understanding the time changes of physical, biological and optical parameters.