巢湖水体漫衰减系数空间差异及其遥感反演

摘要

根据2009年6月巢湖32个样点的实测数据,分析巢湖水体漫衰减系数光谱特征、主导因子、空间分布规律以及400-700nm各波段Kd与Kd(490)之间的关系,并在此基础上,建立了Kd的遥感反演模型.结果表明:巢湖水体Kd具有一致的光谱特征,400-600nm之间Kd随波长的增加呈指数衰减趋势,在600-700nm之间的变化较小,部分点位在波长675nm附近出现峰值,700-900nm之间Kd呈现出类似于纯水的吸收光谱特征;巢湖中无机颗粒物是水体漫衰减的主导因子,有机悬浮物影响次之,CDOM的影响最小;巢湖东半湖区Kd(490)普遍高于西半湖区,巢湖中部Kd(490)等值线分布较密集,湖区其他部分则相对稀疏;利用591、702、842nm处的遥感反射率进行多元线性回归反演得到的Kd(490)与实测Kd(490)之阳J的平均相对误差为7.85%;同时,400-550nm波段范围内,可以利用线性关系和Kd(490)对Kd(λ,λ≠490nm)进行参数化表示,在550-700nm波段范围则可采用常数与Kd(490)的乘积来表示Kd(λ,λ≠490nm).通过遥感反射率反演Kd(490),进而推算Kd(λ),其结果与实测Kd之间的平均相对误差为6.14%.%According to the in situ measured data on 32 sampling sites in Lake Chaohu in June 2009, the spectral characteristics of diffuse attenuation coefficient (Kd ), dominant factors, spatial distribution, as well as the relationship between Kd and Ka (490) in 400-700nm bands were analyzed.On the basis of these analysis, remote sensing inversion model was developed to calculate Kd (490).The results indicate that Kd presented the consistent spectral characteristics.The Kd in 400 -600nm showed a exponential decay trend, but Ka from 600nm to 700nm didn't correlate with wavelength.Due to the higher concentration of phytoplankton in some locations, peak values of Kd appeared at 675nm; but Ka showed a feature that was similar to that of pure water in 700 -900nm.The dominant factor of diffuse attenuation coefficient was inorganic particles in Lake Chaohu, organic particles took the second place, and CDOM held a minimal impact.In general, Kd(490) in the eastern part of the Lake Chanhu was higher than that in the western part.In the central part, the contour lines of Kd(490) were denser than those in other parts of the lake.Kd (490) was inversed by multivariate linear regression model established with Rrs(591 ), Rrs (702) and Rrs(842).And the average relative error between measured and inversed Kd (490) was 7.85％.At the same time, the relationship between Kd (λ, λ ≠490nm) and Kd (490) could be parameterized with wavelength by linear formula in 400 - 550nm.From 550nm to 700nm Kd( λ,λ ≠490nm) was obtained from multiplying Kd(490) by a constant.The relative error between the observed Kd and the Kd(λ),which was calculated by Kd(490) by inversing of the Rrs, was 6.14％.