| Poyang lake is a high dynamic change of seasonal lakes,is the biggest freshwater lake in China,with regulating runoff,providing required water to production of life,water transport,providing habitat for wildlife,and other important functions.But with the rapid economic development of Poyang lake basin in recent years,there are increased pollution and the trend of eutrophication,the Poyang lake ecological security hidden danger,so the protection of Poyang lake ecological and effective monitoring of water body composition changes become badly needed to be.Chlorophyll is a kind of important pigment related to photosynthesis.Chlorophylla concentration can effectively reflect the degree of eutrophication of water bodies.Through thrice sampling data of chlorophyll-a concentrations and water spectrum in this paper,the optical properties,spatial distribution characteristics and ratio absorption coefficient of chlorophyll a in the Poyang lake is analyzed,based on the actual sample data,a chlorophyll-a inversion model of Poyang lake water area is build,and the Poyang lake water chlorophyll-a concentration was studied by means of remote sensing inversion for nearly two years.This paper found that the chlorophyll-a absorption spectrum curve of Poyang lake is not significantly different from other lakes,absorption peaks appear at 440 nm,absorption valley appear at 675 nm,550nm,700 nm.Chlorophyll-a concentration and aψ（670）are highly relevant,the space distribution of aψ（670）can represent the distribution of concentration.Three samples of chlorophyll-a concentrations are: July 2014,0.3929 to 2.2508 mg/m3;September,2014,0.7852 to 4.0837 mg/m3;August 2015,0.7373 to 3.5375 mg/m3.The correlations between chlorophyll-a concentration and measured remote sensing reflectance are analyzed,the results shows that the sensitive wave bands of chlorophyll-a concentration inversion by using the HJ satellite are R3,R1/R3 and R3/R2,R1/R3 band ratio algorithm ultimately is selected,the inversion model of chlorophyll-a is created by sensitive bands and various construction,which is y = 5.6854x2-6.6315 x + 2.8527,determination coefficient R2 is 0.9274,the average error of 17.59%.In this paper,the HJ-CCD satellite image data after image registration,atmospheric correction process,the built chlorophyll-a inversion model is applied to inverse the chlorophyll-a concentration of Poyang lake resents two years.The inversion results show that changes in the concentration of chlorophyll a concentration generally higher in southern,dry season low concentration,the main lake is gradually increased to the coastal concentration trend presentation. |
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