Estimation of chlorophyll-a concentration in the Zhujiang Estuary from SeaWiFS data

The chlorophyll-a concentration is generally overestimated for the southern China coastal waters if the default algorithm of the SeaDAS is employed.An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary,Guangdong Province,China,by using simulated reflectance data.The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands,via a general model by inputting measured water components,i.e.,the suspended sediment,chlorophyll-a,and yellow substance (DOC) concentration data of 130 samples.Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data,and the band combination,R₅R₆/R₃R₄,is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary.This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data.The estimated concentrations have a better accuracy than those obtai obtained from the SeaDAS default algorithm when compared with sea truth data.The new algorithm is d}on_strated to work well and is used to derive a series of image maps of the chlorophyll-a concentration distribution for the Zhujiang Estuary and adjacent coastal areas.