Study Of Remote Sensing Algorithm And The Temporal-spatial Distribution Of CDOM In Bohai Sea And North Yellow Sea Based On MODIS Satellite Data

CDOM(chromophoric dissolvable organic matter)represents an optical determination of water clarity,it can be considered as a proxy for water quality.Investigating the CDOM is the key to understanding marine primary productivity,ecology,biochemistry process,hydrodynamic environment and material transport.Based on MODIS satellite data,a new regional empirical algorithm has been developed over the Bohai Sea and the North Yellow Sea in this paper.Applying this algorithm for long time series satellite remote sensing data(2003-2016),the temporal and spatial distribution and its changing characteristics of CDOM was analyzed.After having a certain understanding of CDOM,based on different data sets,the genetic analysis of its differentiation was carried out.Some significant results are revealed as follows:Based on several in situ data sets,a regional algorithm of CDOM was developed based on the relationship between the CDOM and Rrs,and applying this algorithm for MODIS satellite data.The cross-validation of in situ data set demonstrated that the accuracy of the CDOM algorithm is with R2=0.78,APD=15.9%,RMSE=0.92(ppb).The validation of MODIS showed that the accuracy of the CDOM algorithm is with R2=0.61,APD=25.3%,RMSE=1.18(ppb).The CDOM algorithm was applied to estimate the 14-year(2003-2016)sea surface CCDOM in the Bohai Sea and the North Yellow Sea from the MODIS monthly products.The results showed a significant fluctuation in CCDOM variations on a long-term scale.The highest values of CDOM were observed in the Bohai Sea,middle values in the Bohai Strait,and the lowest values in the North Yellow Sea.Obviously seasonal variations were observed with a long-lasting high CDOM values existing from June to August in coastal waters,while relatively low values in the North Yellow Sea in summer.In spring and fall,a distinct increase appeared in the North Yellow Sea.Based on different data sets,the genetic analysis of its differentiation was carried out.There are two sources for CDOM in waters,namely terrestrial CDOM and autochthonous CDOM.High CDOM values in the nearshore coastal waters were mostly related to terrestrial inputs,while the CDOM in the offshore regions were mainly due to the autochthonous productions.Furthermore,ocean currents played an important role in variations of CDOM in the Bohai Sea and the North Yellow Sea,especially in variations of CDOM in the Bohai Strait.A strong relationship was observed between multiyear mean distributions of CCDOM and the current field,with high CCDOM found in the BSCoW areas and low CCDOM found in the BSCW areas,but vary seasonally.After having a certain understanding of CDOM and ocean currents,we discussed the possibility of using CDOM and Temperature to identify water masses from the space by satellite data.