基于实测光谱的白洋淀叶绿素a浓度反演

Inversion of chlorophyll a concentration in Baiyangdian Lake based on measured spectra

内陆水体叶绿素a浓度决定其浮游生物含量,是衡量水体富营养化程度的主要指标,更是影响水体表观反射率光谱的重要因素之一。三波段生物光学模型能有效避免二类水体中悬浮物与化学物质等因素的影响,准确估算叶绿素a浓度。以雄安新区白洋淀为研究区域,利用实测水体光谱及水体叶绿素a浓度,分析水体光谱特征,利用穷举法确定三波段因子位置,建立三波段反演模型及精度验证,最后对结果进行分析评价。结果表明,在λ_(1)=673 nm,λ_(2)=729 nm,λ_(3)=782 nm处,三波段模型反演因子[R_(rs)^(-1)(673)-R_(rs)^(-1)(729)]R_(rs)(782)与叶绿素a浓度的相关系数最高为0.82。该模型的决定系数、均方根误差、平均绝对误差、平均相对误差分别为0.67、3.61μg/L、2.86μg/L、26.06%,表明对于悬浮物以及化学物质较高的水体,三波段模型相较于波段比值与单波段模型具有很好的反演精度。该研究为白洋淀叶绿素a浓度反演提供了一定的理论依据和技术支持,有助于白洋淀水质持续监测,也为后续使用三波段模型反演二类水体叶绿素a浓度提供了算法支持。

The concentration of chlorophyll a in inland water determines the plankton content,which is a main index to measure the eutrophication degree of water,and is also one of the important factors affecting the apparent reflectance spectrum of water.The three-band bio-optical model can effectively reduce the influence of suspended matter and chemical substances in Class Ⅱ water during the inversion process and accurately estimate the concentration of chlorophyll a.Taking Baiyangdian Lake in Xiongan New Area,China,as the research area,the spectral characteristics of water were analyzed by using the measured water spectrum and chlorophyll a concentration,the position of three-band factors was determined by using the exhaustive method,the three-band inversion model was established and the accuracy was verified,and finally the results wreanalyzed and evaluated.The results show that at λ_1=673 nm,λ_2=729 nm,λ_3=782nm,the maximum correlation coefficient between the inversion factors of the three-band model[R_(rs)~(-1)(673)-R_(rs)~(-1)(729)]R_(rs)(782) and chlorophyll aconcentration is 0.82.The determination coefficient,root mean square error,mean absolute error and mean relative error of the model are 0.67,3.61 μg/L,2.86μg/L and 26.06%,respectively,indicating that for the water with high suspended matter and chemical substances,the three-band model has a good inversion accuracy compared with the wave segment ratio and single-band model.This study provides a certain theoretical basis and technical support for the inversion of chlorophyll a concentration in Baiyangdian Lake,which is helpful for the continuous monitoring of water quality in Baiyangdian Lake,and also provides an algorithmic support for the inversion of chlorophyll a concentration in Class Ⅱ water using three-band model in the future.