Variations of absorption coefficient of seawater in the Pearl River Estuary and a hyperspectral retrieval model for an algal bloom
珠江口藻华水体总吸收系数的变化特性及高光谱反演模式

In August 2007, bio-optical measurements were collected over a period of 16 days in the Pearl River Estuary, and an algal bloom was detected. In situ radiometric data were obtained using a marine optical buoy. The variations in absorption properties and ocean color of seawater and their internal relationship were investigated. The results show that the colored detrital matter (CDM), especially the colored dissolved organic matter (CDOM), had large contributions to the total absorption of seawater at blue waveband, while the absorption contribution of phytoplankton tended to increase with the rapid increase of chlorophyll a concentration when the bloom occurred. Linear regression was used to express the spectral correlations between total absorption coefficients at 443nm and at other visible bands, and the blue-to-red ratio of absorption showed a big effect on the spectral distribution of spectral reflectance. An empirical hyperspectral ocean color model for retrieving the absorption coefficient was developed, and the calculated and measured results showed small discrepancy, with relative root mean square error being less than 24% over the visible spectrum.