Remote Sensing Inversion Chromophoric Dissolved Organic Matter In Typical Inland Water

Chromophoric Dissolved Organic Matter(CDOM),also called yellow substance,is a kind of dissolved organic matter widely distributed in natural waters.CDOM together with suspended solids and phytoplankton are all the main objects of ocean color remote sensing study. The application of remote sensing technology promoted the research of water optical properties changes in large scale of time and space range.Compared with suspended solids and phytoplankton,the studies of CDOM inversion is relatively small.And the optical properties of sea waters are more simpler,and often chosen as the research areas. Conversely,the studies in Coastal and inland waters are relatively small amount.This article select Guanting Reservoir and taihu lake,two typical inland waters as the research areas,take the absorption coefficient of CDOM as concentration index. In this paper, the main innovation points are as follows:(1) Combining QAA_V4, QAA_V5,two improved version of QAA and QAA-CDOM, this paper proposed two innovative methods, QAA(V4)-CDOM and QAA(V5)-CDOM, used in remote sensing inversion of CDOM.(2) This paper divided water surface spectral data of taihu lake and guanting reservoir into two kinds,based on the spectral characteristics.Then,for each kind,QAA(V4)-CDOM and QAA(V5)-CDOM were taken for CDOM inversion respectively.To a certain extent, it solved the of seasonal and regional restrictions of the inversion method.In this paper, the main contents and conclusions are as follows:(1) In this paper,QAA-E,Dong Qiang’s method(called QAA-FOC in this paper), QAA-CDOM,QAA(V4)-CDOM and QAA(V5)-CDOM,totally five methods used for CDOM inversion.The results showed that,QAA(V4)-CDOM is the best method for Guanting reservoir,and QAA(V5)-CDOM is the best method for Taihu lake.But the precision of inversion results of taihu lake still need to increase. So this paper divided water surface spectral data of taihu lake into two kinds, and take QAA(V4)-CDOM and QAA(V5)-CDOM for CDOM inversion respectively.The inversion accuracy was improved after classification.(2) The same with Taihu lake,60 points of Guanting reservoir was also divided into two kinds.Integrated Guanting reservoir and taihu lake, after analysising the correlation of each two band ratio with CDOM of each kinds respectively, and also taking hyperspectral data band set into account, two band ratios Rrs(665)/Rrs(443)å'Œ Rrs(620)/Rrs(443)were selected,and two empirical models were established. The average relative error(MRE) of the inversion results for each kind are 12.1% and 18.8% respectively and the root mean square error(RMSE) are 0.157 m-1and 0.192 m-1.(3) This paper analyzed the correlation between CDOM and remote sensing reflectance at each band respectively, according to seasons, study areas and V4,V5 classes, and establish experience CDOM inversion model based on single band.The results showed that the model of single study area of spring and winter are the best.Due to the interference of phytoplankton, the model for summer and autumn is not ideal. The modelsrelated to different research areas and different seasons data are also not ideal.Above all, it is difficult to invert CDOM based on a single band.(4) Classification semi-analytical inversion method and band ratio experience inversion model, are all used in hyperspectral data CDOM inversion.There are two type hyperspectral data:CHRIS and MERIS. There is no quasi-synchronous measured data to evaluate the accuracy of the inversion results for Guanting reservoir,so this paper just compares the semi-analytical method and the experience method inversion results.The result show that the inversion results of the two methods’ result have unified distribution. Taihu lake has 75 quasi-synchronous measured points used for precision inspection.Five experiments cover four seasons.Spring and winter have better inversion results.Because of the influence of chlorophyll, summer and autumn’s inversion results accuracy remain to be promoted...