三峡水库水体漫衰减系数光学特性及其遥感反演

摘要

By using the in situ measured data of spectral reflectance and water quality parameters in Aug. 22 - 24, 2009, this study analyzed the spectral characteristics and affecting factors of diffuse attenuation coefficient( Kd ) of the Three Gorges Reservoir,and built a retrieving model of Kd (490)at band 490nm. In addition, Kd (490)was inversed by using CCD image of HJ-1 satellite in July 21,2009. The results showed that the attenuation peaks were not distinct at bands 440nm and 675nm owing to the high content of non-pigment particulates in the water. The dominant affecting factors were absorption of particulates and total scattering of water body, while average contributions of the four bands( i. e. 440,550,613 and 675nm) were 45.48％ and 38.21％, respectively; Kd strongly power correlated with the concentration of non-pigment particles between 400 to 700nm. Besides, the average relative error of inversed vs. measured Kd(490) was 17.89％ for ground-measured RTs, whereas the relative error for images data was 28.38％; Kd(490) of the study area was concentrated from 6 to 7 m-1 , which accounted for 83.60％ of the study area.Additionally, Kd(490) of the tributaries of the reservoir was lower than the main stream, which indicated that the content of particulates in tributaries was relatively low.%根据2009年8月22-24 日实测的三峡水库水体的光谱数据以及水质参数,对三峡水库漫衰减系数的光学特性及影响因子进行分析研究,构建了490nm处漫衰减系数的Kd(490)反演模型,并利用环境一号卫星CCD数据对2009年7月21日的三峡水库Kd(490)进行反演.结果表明:由于水体中非色素颗粒物的含量较高,使得研究区大部分点位的Kd值在440nm和675nm处的衰减峰值不明显,对Kd占主导地位的影响因子是颗粒物的吸收作用以及水体的总散射作用,在所选的四个特征波段(440、550、613和675nm)处,其贡献率的均值分别为45.48%和38.21%;在400-700nm波段范围,Kd与非色素颗粒物浓度具有很好的幂函数关系.利用地面实测遥感反射率模拟环境卫星第三波段构建Kd(490)反演模型,其平均相对误差为17.89%,直接利用卫星数据反演的相对误差为28.38%;研究区中Kd(490)主要集中在6-7m-1,占研究区域面积的83.60%,相比而言,入库支流的Kd(490)较干流要低,表明支流颗粒物含量相对较低.