真光层深度的遥感反演及其在富营养化评价中的应用

真光层深度直接影响水体中浮游植物的分布和初级生产力以及水体生态环境,是水生态研究的一个重要参数.利用2006年10月24日～11月2日太湖水下实测光谱数据和光合有效辐射(PAR)数据,通过数据的处理和分析,尝试建立真光层深度与水面以下遥感反射率的关系模型,并利用真光层深度与透明度的关系,建立水体富营养化真光层深度评价模型.研究结果表明:真光层深度与归一化遥感反射率具有很好的相关性;选用特定波段的归一化反射率作为变量,建立两者的关系模型能较好的反演真光层深度,所建立的模型算法中,指数模型拟合方程的综合效果好于其他模型,波段比值算法反演精度要好于单波段算法;利用利用真光层深度进行富营养化评价具有一定的应用价值,利用该模型对太湖水体进行富营养化评价,得出太湖西部湖区大部分已富营养化,东部湖区处于中营养化和轻度富营养化状态.

Euphotic depth: retrieval from in situ reflectance and application in assessing eutrophication

Euphotic depth is one of the most important variables in the study of an aquatic ecological system. This variable has direct effects on the distributing of phytoplankton and net primary production of waters. The underwater reflectance and photosynthetic available radiation (PAR) data were collected from Oct. 24 to Nov. 2, 2006 in Taihu Lake. For retrieving euthotic depth, a variety of relationship models were attempted in which in situ reflectance at a single band or band ratio was regressed onto measured euthotic depths. The eutrophication of Taihu Lake was then assessed based on the correlation of this parameter to transparency which was derived from the estimated euthotic depth. The results indicate that euphotic depth and normalized in situ reflectance are highly correlated, and the relationship models can be sued to accurately retrieve euphotic depth from a specified spectral variable; among the algorithms examined, exponential equations performed better than other relationships; and the models with the band-ratio resulted in higher retrieving accuracy than those using a single band; the assessment of the eutrophication with euphotic depth has proved to be a valuable and applicable approach. The application of this model to Taihu lake indicates that the western area of the lake was serious eutrophic, and the eastern area of the lake was mesotropher and light eutrophic.