Inversion Model Of Chlorophyll Concentration In Poyang Lake Based On Multi-source Remote Sensing Information

As the largest freshwater lake in China,Poyang Lake is also an important water source in the middle and lower reaches of the Yangtze River.It plays an important role in regulating flood storage and providing water for living and production.Therefore,it is particularly important to conduct long-term effective monitoring of the water quality of Poyang Lake.This paper takes Poyang Lake as the research area,and analyzes the chlorophyll concentration measured by the basic indicators of water primary productivity and lake health.Based on field spectral acquisition data,water sample collection data,MODIS,Landsat8-OLI satellite data,various information Source synchronization data,conducted the following research and got relevant conclusions:1.The surface spectral curves of the Poyang lake research area were collected by using Fieldspec4,a terrestrial object spectrometer produced in the United States,and the obtained spectral information was analyzed characteristically to explore the correlation between the chlorophyll concentration of water quality indicators and spectral reflectance.Based on the correlation between the initial water body spectral curve and the normalized water body curve and water quality parameters,the sensitive bands R669nm,R533nm and R690nm were found,and the sensitive bands and their band combinations selected by correlation were used as variable factors to construct hyperspectral data.A semi-empirical inversion model of the linear,quadratic,exponential,exponential,and logarithmic functions of the sensitive band and its band combination and chlorophyll concentration based on hyperspectral data is constructed,and the inversion accuracy of the constructed model is verified.Finally,the quadratic polynomial semi-empirical inversion model based on spectral data is obtained with the highest correlation,the smallest error and the best fitting effect.This is consistent with the model type obtained by most researchers,and also verifies the application of the model.Credibility and universality are a viable inversion method.2.Explore the correlation between chlorophyll concentration and remote sensing data,analyze sensitive bands or band combinations,construct the regression empirical inversion models of chlorophyll concentration and remote sensing data respectively for the self-defined model algorithm and RI model algorithm for calculating remote sensing reflectance,the necessary accuracy verification and analysis are performed on the inversion models obtained by the two algorithms.In addition,the two algorithms are compared and analyzed.The results show that,based on the calculation of surface reflectance of remote sensing satellites,the inversion model obtained by RI model algorithm is better than the inversion model obtained by self-defined model algorithm in terms of correlation,error analysis and inversion fitting.Therefore,it is more suitable for inversion of water quality parameters of Poyang Lake.3.Based on the optimal inversion models of MODIS and Landsat,the calculation models of TSI and TSI_M based on remote sensing data of MODIS and Landsat were obtained by using Carlson's trophic state index TSI and modified TSI_M,respectively.The evaluation results of Poyang Lake water body in the study area in the middle trophic state were obtained,and verified from the Water Quality Bulletin of Jiangxi Province in 2010-2017 on the water quality data of Poyang Lake.The model was applied to Landsat series image data from 2009 to 2018 to analyze the temporal and spatial dynamic distribution of chlorophyll concentration in Poyang Lake during the past ten years.From the retrieved chlorophyll concentration analysis,the highest chlorophyll concentration occurred in 2010.In spatial distribution,the chlorophyll concentration in the southern part of the lake area was significantly higher than that in the northern part,mainly because the Poyang Lake flows from south to north,with strong fluidity,chlorophyll a is not easy to aggregate,and the absorption and degradation of chlorophyll a by phytoplankton during the flow process is also The important reason why the south is higher than the north.