太湖水体漫射衰减系数的光学特性及其遥感反演模型

Optical properties and remote sensing retrieval model of diffuse attenuation coefficient of Taihu Lake water body

利用2007年11月8—22日太湖实测光谱数据和水质分析数据,分析了秋季太湖水体漫射衰减系数(Kd)的光谱特性及其影响因子,并在此基础上,利用水面以上遥感反射率,以490nm波长的漫射衰减系数[Kd(490)]作为中间变量,建立了漫射衰减系数与水面以上遥感反射率的遥感反演模型.结果表明:在可见光波段范围内,秋季太湖水体大部分点位的漫射衰减系数随波长的增加呈指数递减趋势;由于部分点位浮游藻类的含量较高,对漫射衰减系数影响较大,导致这些点位的漫射衰减系数在波长675nm附近出现峰值;无机悬浮物对漫射衰减系数的影响大于有机悬浮物,主要是由于悬浮物中无机悬浮物的含量远大于有机悬浮物.漫射衰减系数与遥感反射率具有很好的相关性,以Rrs(550)、Rrs(675)、Rrs(731)作为自变量,与Kd(490)进行回归分析,得出Kd(490)与Rrs(731)具有很好的线性关系,而利用Rrs(550)、Rrs(675)、Rrs(731)进行多元线性回归的效果(R2>0.96)好于单波段[Rrs(731)]算法.

The spectral and chemical analytical data of Taihu Lake water quality in Nov. 8-22, 2007 were used to analyze the spectral characteristics of diffuse attenuation coefficient （Kd ） of the water body in autumn and related affecting factors. On the basis of this analysis, the Kd at band 490 nm, Kd （490）, was used as a variable to build the relationship between Kd and remote sensing reflectance. The results indicated that within the scope of visible band, the Kd of the water body at most locations of Taihu Lake presented an exponent decreasing trend with the increase of wave length. Due to the higher concentration of phytoplankton in some locations, a peak value of Kd was presented at band 675 nm. Non-organic suspended particles, because of their higher content in suspended sediment, had larger effects on Ka than organic suspended ones. There was a good correlation between Ka and remote sensing reflectance. Taking Rrs （ 550）, Rrs （675） and Rrs （ 731 ） as independent variables and doing regression analysis with Kd （490）, a good linear relationship was found between Kd （490） and Rrs （731 ）, and muhi-variate linear regression analysis using variables Rrs （ 550）, Rrs （675） and Rrs （731 ） could get better effect （ R^2 〉 0.96 ） than the regression analysis using variable Rrs （731 ）.