水体红波段反射光谱对叶绿素浓度变化的响应

Quantitative Analysis of Chlorophyll-a Reflectance Spectrum in Red Spectral Region of Water

在不考虑叶绿素荧光效应的前提下，基于水体光学活性因子藻类叶绿素、有色可溶性有机物及非藻类颗粒物的吸收和后向散射系数，根据前向辐射传输模型模拟水面以上遥感反射率，分析了藻类叶绿素红光峰强度和波长位置随浓度的变化规律。结果发现：叶绿素浓度为1～50 μg·L-1时，红光峰强度和叶绿素浓度呈较好的线性关系，随叶绿素浓度的增加，线性关系越来越不明显。当叶绿素浓度为1～1 000 μg·L-1时，则呈现较好的对数关系;随叶绿素浓度的增加，红波段反射峰波长位置按对数规律逐渐向长波方向移动，不同水色组分的水体，其叶绿素在红波段的光谱反射特性随浓度的变化规律是一致的;此外，对比研究显示红波段反射峰特征不同于荧光光谱。

The chlorophyll-a concentration in waters is one of the main parameters of water color remote sensing in case Ⅱ waters. There is a reflectance peak in red band region because of inherent optical properties. Based on the coefficients of absorption and backscattering of waters, colored dissolved organic matter （CDOM）, tripton and chlorophyll-a, the reflectance of remote sensing was simulated according to the forward radiation transfer model without the consideration of fluorescence peak. The re- flectance peak intensity and reflectance peak position at different wavelengths in red band region were analyzed with different chlorophyll-a concentration. There is a good linear relationship between the red reflectance peak intensity and chlorophyll-a con- centration when the chlorophyll-a concentration is 1-50 μg·L-1. But the linear relationship between the reflectance peak intensi- ty and chlorophyll-a concentration will decrease with the increasing chlorophyll-a concentration. When chlorophyll-a concentra- tion is up to 1 000 μg·L-1 , the logarithm relationship between the reflectance peak intensity and chlorophyll-a concentration is better than linear relationship. The wavelength position of reflectance peak in red band region will shift towards larger wavelength at logarithmic growth rate with increasing chlorophyll-a concentration, and the logarithm relationship will be more apparent with the inoreasing chlorophyll-a concentration. The same trend happens to the reflectance peak intensity and the wavelength position of peak in red region with different in water constituents, such as CDOM, tripton and so on. Furthermore, according to the comparison with fluorescence peak, the authors also found that the reflectance peak intensity and the wavelength position of peak in red region are different from those of the fluorescence peak.