Under the support of the remote sensing and geographical information system(GIS) techniques,we acquire the land use data in 1990 and 2008 regarding 6 inhabited islands,namely Longxue Island,Hengmen Island,Weiyuan Isla...Under the support of the remote sensing and geographical information system(GIS) techniques,we acquire the land use data in 1990 and 2008 regarding 6 inhabited islands,namely Longxue Island,Hengmen Island,Weiyuan Island,Qi'ao Island,Hengqin Island and Gaolan Island in Pearl River Estuary.By using dynamic degree of land use,land use change intensity,relative change rate and other indicators,we conduct quantitative description,and thus quantitatively and qualitatively analyse characteristics of temporal evolution and law of spatial pattern change concerning land use of each island.The study indicates that in the period 1990-2008,the area of construction land and water in 6 islands increased,while the area of agricultural land and unused land increased in some islands and decreased in others.The land use change shows spatial disparity;the holistic land use change degree in Hengmen Island is higher than that of other islands;the dynamic degree of land use,intensity of land use,and relative change rate differ in different islands.展开更多
This study aims to develop new algorithms to retrieve sea surface parameters including concentrations of Chlorophyll a （Chl a） and Suspended Particulate Matter （SPM）, and absorbance of Colored Dissolved Organic Ma...This study aims to develop new algorithms to retrieve sea surface parameters including concentrations of Chlorophyll a （Chl a） and Suspended Particulate Matter （SPM）, and absorbance of Colored Dissolved Organic Matter （aCDOM） by incorporating the contribution of red bands to make them more adaptable to case 2 waters. Optical remote sensing algorithms have demonstrated efficient retrieval of Chl a, SPM, and aCDOM, yet they are not very accurate especially for coastal areas. It has also been found that the default algorithm has overestimated Chl a in the Pearl River Estuary, and shown poor correlation for CDOM absorbance. By incorporating the red band ratios into the algorithm, a correction effect has been shown, which improves the accuracy of quantifying the actual concentration. Modeling and data fitting of the algorithm have been done based on 61 data samples collected in the Pearl River estuary during a cruise from 3 to 11 May 2014. The study also attempts to modify the aerosol correction bands used in SeaDAS to prevent saturation of these bands. The modified algorithms showed an R-Square value of 0.7289 for Chl a fitting, and 0.7338 for CDOM fitting, and corrected overestimation of Chl a concentration in the Pearl River estuary.展开更多
The distributions of estuarine colored dissolved organic matter（CDOM）are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ d...The distributions of estuarine colored dissolved organic matter（CDOM）are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm（aCDOM（400））in the Zhujiang（Pearl River）Estuary（ZJE）.The algorithm uses band ratios of Rrs（667）/Rrs（443）and Rrs（748）/Rrs（412）.By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite（MODIS/Aqua）data from 2002 to 2014,seasonal climatology aCDOM（400）in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM（400）exponentially decreased（y=aebx,b〈0）,but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon（DOC）in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.展开更多
基金Supported by Guangdong 908 Special Plan(GD908-01-02)The Marine Science and Technology Director Foundation of South China Sea Branch (0871)
文摘Under the support of the remote sensing and geographical information system(GIS) techniques,we acquire the land use data in 1990 and 2008 regarding 6 inhabited islands,namely Longxue Island,Hengmen Island,Weiyuan Island,Qi'ao Island,Hengqin Island and Gaolan Island in Pearl River Estuary.By using dynamic degree of land use,land use change intensity,relative change rate and other indicators,we conduct quantitative description,and thus quantitatively and qualitatively analyse characteristics of temporal evolution and law of spatial pattern change concerning land use of each island.The study indicates that in the period 1990-2008,the area of construction land and water in 6 islands increased,while the area of agricultural land and unused land increased in some islands and decreased in others.The land use change shows spatial disparity;the holistic land use change degree in Hengmen Island is higher than that of other islands;the dynamic degree of land use,intensity of land use,and relative change rate differ in different islands.
基金This work is supported by the Hong Kong Innovation and Technology Fund under grants of ITS/272/11 and ITS/259/12, the General Research Fund of Hong Kong Research Grants Council （RGC） under grants CUHK 402912 and 403113, the National Natural Science Foundation of China （Grant No. 41376035）, and the direct grants of the Chinese University ofHong Kong. The authors are grateful to Dr. Chunyan Shen, who provided with substantial supports to the in-sire data collection.
文摘This study aims to develop new algorithms to retrieve sea surface parameters including concentrations of Chlorophyll a （Chl a） and Suspended Particulate Matter （SPM）, and absorbance of Colored Dissolved Organic Matter （aCDOM） by incorporating the contribution of red bands to make them more adaptable to case 2 waters. Optical remote sensing algorithms have demonstrated efficient retrieval of Chl a, SPM, and aCDOM, yet they are not very accurate especially for coastal areas. It has also been found that the default algorithm has overestimated Chl a in the Pearl River Estuary, and shown poor correlation for CDOM absorbance. By incorporating the red band ratios into the algorithm, a correction effect has been shown, which improves the accuracy of quantifying the actual concentration. Modeling and data fitting of the algorithm have been done based on 61 data samples collected in the Pearl River estuary during a cruise from 3 to 11 May 2014. The study also attempts to modify the aerosol correction bands used in SeaDAS to prevent saturation of these bands. The modified algorithms showed an R-Square value of 0.7289 for Chl a fitting, and 0.7338 for CDOM fitting, and corrected overestimation of Chl a concentration in the Pearl River estuary.
基金The National Key Research and Development Progam of China under contract No.2017YFA0603003the National Basic Research Program(973 Program)of China under contract No.2015CB954002+3 种基金the Public Science and Technology Research Funds Project of Ocean under contract No.201505003the National Natural Science Foundation of China under contract Nos41676170,41676172,41476155,41621064 and 41406202the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,State Oceanic Administration of China under contract No.SOEDZZ1801the Research Startup Project of Nanjing Instiute of Geography and Limnology,Chinese Academy of Sciences under contract No.Y7SL051001
文摘The distributions of estuarine colored dissolved organic matter（CDOM）are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm（aCDOM（400））in the Zhujiang（Pearl River）Estuary（ZJE）.The algorithm uses band ratios of Rrs（667）/Rrs（443）and Rrs（748）/Rrs（412）.By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite（MODIS/Aqua）data from 2002 to 2014,seasonal climatology aCDOM（400）in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM（400）exponentially decreased（y=aebx,b〈0）,but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon（DOC）in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.
