内陆水体后向散射系数模拟研究

在利用半分析方法结合光学闭合原理模拟水体后向散射系数的过程中，参考波长的选择对最终结果有较大影响.为了得出最佳参考波长的影响因子，利用太湖、巢湖和滇池的野外实测数据，对后向散射系数进行模拟，进而分析水体的最佳参考波长与其对应的水质参数浓度之间的变化规律.同时，建立了太湖、巢湖和滇池水体的后向散射系数曲线的幂函数光谱模型，获得的光谱指数分别为2.643±0.317、 2.719±0.242、 1.638±0.534.结果表明：①以整个湖泊为研究对象时，最佳参考波长随着湖泊水体中总颗粒物浓度c_SPM、有机颗粒物浓度c_SPOM和叶绿素浓度c_CHL平均值的增大而向长波方向移动，太湖、巢湖和滇池水体的最佳参考波长分别为695、 720和730 nm；②以单个湖泊的各个样点为研究对象时，由于内陆湖泊光学特性的复杂性，最佳参考波长的影响因子存在一定差异，但c_SPM是一个共同的影响因子.此外，过高的c_CHL将削弱水质参数浓度与最佳参考波长间的规律性；③在以无机颗粒物为主的水体中，后向散射系数与总颗粒物浓度之间存在更好的相关性，如在太湖水体中，R²达到0.852.

Simulation of Backscattering Coefficients of Inland Waters

When we simulated backscattering coefficients (b(bp)) using quasi-analytical algorithm and optical closure theory, it was found that the position of reference wavelength (lambda(0)) had great impact on final results. In order to identify influence factors of the optimum lambda(0), datasets of Lake Taihu, Lake Chaohu and Lake Dianchi were used. After simulating of b(bp), the relationship between optimum lambda(0) and associated water quality parameters were analyzed. Meanwhile, power functions were utilized to model b(bp) spectra, and spectral slope parameters of Lake Taihu, Lake Chaohu and Lake Dianchi were 2.643 +/- 0.317, 2.719 +/- 0.242, 1.638 +/- 0.534, respectively. The results indicate that: (1) When the whole lakes are taken as objects of study, the lambda(0) should be changed to longer wavelength with the increasing of total suspended particle matter concentration (c(SPM)), suspended organic particle matter concentration (c(SPOM)) and chlorophyll a concentration (c(CHL)), the optimum location of lambda(0) of Lake Taihu is 695 nm, Lake Chaohu is 720 nm and Lake Dianchi is 730 nm; (2) When the samples in lakes are taken as objects of study, the influence factors are different due to the complexity of optical properties of inland waters. But it is to be noted that, c(SPM) is a key factor in common. Besides, the regularity mentioned above should be weakened with high c(CHL). (3) The relationship between b(bp) and c(SPM) is much stronger in the waters with suspended particles dominated by inorganic particles, in Lake Taihu, for example, relationship between these two variables is strong with R2 = 0.852.