Retrieval Of Chlorophyll A In Inland Lake Based On MERIS Data

Ocean color remote sensing technology is using sensor surface emission spectrum of radiation received and related data processing, so as to get water for some basic information technology. In plankton chlorophyll, inorganic suspended matter and organic matter are three factors that determine the Yellow color. The focus of the radiation spectrum is mainly concentrated in the visible to near infrared band. Through the ocean color remote sensing technology can be obtained affecting optical properties of component concentration in water, detection of surface water composition, for marine primary productivity prediction, Ocean Flux study, marine ecological environment monitoring, ocean dynamics research, marine fisheries development and management services has an important role. As a marine satellite remote sensing is an important branch of, ocean color remote sensing have decades of development history, from existing research results can be found:in the remote sensing inversion of Chlorophyll Concentration Retrieval Case I water, using the relationship between chlorophyll concentration and blue and green band contrast linear regression algorithm has higher inversion precision; I water color quantitative remote sensing inversion methods gradually mature, has formed many widely recognized global business algorithm.But for water components more complex Case II water, the sensor receives a band reflectance depends not only on a color variable, but on to the water of different water group composed of the joint contributions, at this time, a simple statistical model can no longer be a high accuracy and a high degree of unity of the global. Nonlinear algorithm, principal component analysis method, neural network method, though to a certain extent solve the problem of color components and inversion However, the term can not escape the high dependence on the measured data. Case II water color quantitative remote sensing inversion problem is still the bottleneck of the ocean color remote sensing monitoring, establishment of GM’s global atmospheric correction and color inversion algorithm or a heavy process, to explore the existence of the universal Case II water atmospheric correction and color inversion algorithm is an academic debate hot.Poyang Lake as one of the largest freshwater lakes in China, the suspended sediment as one of the important parameters of the color and many achievements have been gained in the waters, many scholars in this field has been some achievements. However chlorophyll a as an important color parameters and the important index of water quality, in the study of Poyang Lake is currently in the blank, this paper choose the Poyang Lake as the study area, from the actual situation of Poyang Lake of, on the measured spectra and chlorophyll concentration data based, satellite remote sensing data, from space to explore the waters of chlorophyll concentration distribution and analysis caused by the reasons for the existence of the waters of the concentration diiference.1.Measured spectral measurements and chlorophyll concentration sample analysis.Water spectrum measurement using the Optics HR2000 company’s Ocean optical fiber spectrometer, the spectrometer band range of 200 nm～1100 nm, a total of 2048 bands, the maximum spectral resolution of 0.035 nm (FWHM). The NASA (National Aeronautics and space) and simbios (simulation of biological structures) recommended observation geometry:observation instrument plane and the plane of the incident solar angle o v=135 degrees, instrument and surface normal angle theta v=40 degrees. The method above the water surface spectroscopy measurements. The water samples collected from the field were brought back to the laboratory to measure the concentration of chlorophyll a in water.2.Comparison and analysis of different atmospheric correction algorithms、Atmospheric correction was performed by four atmospheric correction algorithms, FLAASH,6S, BEAM, QUAC, and two scene MERIS images of 2005 and 2011. Then the four different atmospheric correction algorithms are compared and analyzed with the measured spectral data. Finally, four kinds of atmospheric correction algorithm accuracy difference, find out the correction effect of the best atmospheric algorithm. Through the comparative analysis, it is concluded that the overall effect of the FLAASH atmospheric correction algorithm is the best, the coefficient of determination (R2) is 0.6, and the relative error (RE) is 31.43%.3. Poyang Lake chlorophyll concentration inversion analysis.From the collection of the measured spectral data, draw the curves of spectral reflectance, characteristics and regularity of the spectral curves were compared, again for different chlorophyll a inversion algorithm, combined with the field measured spectral data and chlorophyll a concentration data, establish related data collection and analysis, through the analysis of the obtained measured spectral data and chlorophyll a concentration dependent relationship, find two correlated best with the band, then successively combine the chlorophyll-a retrieval model analysis, error and precision of each model. Finally, the simulation results show that Y4 model (Rrs490/Rrs5600) fitting results best, after 2005 and 2011 two scene MERIS images of radiometric calibration, geometric correction and atmospheric correction, the final corrected image of Poyang Lake chlorophyll-a inversion can be seen temporal and spatial variation of the Poyang Lake chlophyll-a concentration distribution is:from the space, the northern Poyang Lake, central water chlorophyll a concentration is less, the distribution of more concentrated in the eastern, Western and southern Lake. From the point of view of the time, the western and southern waters of Poyang Lake in 2005 was relatively small, and the chlorophyll a concentration in the West and south of the water was significantly increased in the western and southern part of the waters in 2011.