| Based on the measured remote sensing reflectance and concurrent chlorophyll a (Chl-a) concentration in Taihu Lake from January 7 to 9 and July 29 to August 1, 2006, this study comparatively analyzed the estimation precision of three-band-model, two-band-model, reflectance peak position method and first derivative method, and further discussed the feasibility of the four methods to estimate Chl-a using remote sensing image. The data set of two samplings contained widely variable total suspended matter (12.24-285.20 mg·L-1), Chl-a (4.83-155.11 μg·L-1) and chromophoric dissolved organic matte absorption coefficient at 440 nm (0.27-2.36 m-1). The former four methods all got high precisions on Chl-a concentration estimation in Taihu Lake with determination coefficients (r2) of 0.813, 0.838, 0.872 and 0.819, respectively. The root mean square error (RMSE) between measured and estimated Chl-a concentrations using the four models was 13.04, 12.12, 13.41 and 12.13 μg·L-1, respectively, and the relatively error (RE) was 35.5%, 34.9%, 24.6% and 41.8%, respectively. Although the reflectance peak position method had the highest estimation precision, it was difficult to be applied on remote sensing image due to lacking spectral channel. The three-band-model and two-band-model had higher estimation precisions than the first order differential method and good application foreground in Chl-a retrieval using remote sensing image. The r2, RMSE, RE of ［R-1(665)-R-1(709)］×R(754) in three-band-model and R(709)/R(681) in two-band-model based on simulation MERIS data were 0.788, 13.87 μg·L-1, 37.3%, and 0.815, 12.96 μg·L-1, 34.8%, respectively. The results in this study demonstrated MERIS data could be applied to retrieve Chl-a concentration in turbid Case-Ⅱ waters as Taihu Lake. |
