Modeling Chlorophyll-a Concentration in Taihu Lake Based on different Trophic State

摘要

In this paper, we want to search for the hyperspectral remote sensing bands most sensitive to chlorophyll-a concentrationin different trophic states. Through repeated measurements in Taihu Lake, a large quantity of hyperspectral reflectancedata and chlorophyll-a concentration data of lake were obtained from June to September of 2004 and 2005. The eligiblehyperspectral data were analyzed to calculate remote sensing reflectance of water in Taihu Lake, and the data ofchlorophyll-a concentration obtained from laboratory analysis were used to calculate Trophic State Index. According tothe actual condition of Taihu Lake, the hyperspectral data were divided into three groups: mesotropher, eutropher andhyper eutropher. In each trophic state, chlorophyll-a concentration was then regressed against to identify the mostsensitive hyperspectral bands. From the established regression models, we can get the conclusion: chlorophyll-aconcentration is correspondingly lower under mesotrophic state, badly influenced by suspended matter, the spectralfeature of chlorophyll-a is not evident, and the accuracy of regression model in this trophic state is not so satisfactory; ineutrophic state, differential algorithm has better retrieval result, the linear model based on this algorithm has the bestestimation resu under hyper eutrophic state, the estimation accuracy is higher than the other two states as a whole. Thefitting precision is the highest using the band ratio R719/R670 as independent variable in the quadratic equation model.