Optical remote sensing is a crucial component of the ocean observation system.However,the complex interactions between the ocean and atmosphere limit its observation capability and hinder the advancement of quantitati...Optical remote sensing is a crucial component of the ocean observation system.However,the complex interactions between the ocean and atmosphere limit its observation capability and hinder the advancement of quantitative applications and support capacity.Polarimetric remote sensing,as an advanced detection technology,investigates the anisotropic characteristics of electromagnetic waves perpendicular to the direction of propagation.Serving as an extension of conventional optical remote sensing,it significantly improves the accuracy of feature identification and quantitative estimation.As the most classical polarization feature,the Degree of Polarization(DoP)feature has been widely applied in various scenarios.In this study,the spatial distribution of the DoP feature over the 2πobservation space under oceanic conditions is thoroughly investigated through theoretical simulations and sample measurements.Our findings suggest that the DoP feature lacks sufficient sensitivity and versatility to be used independently in ocean observation scenarios.To address this limitation,a novel feature,namely the Angular Polarization(AP)feature,is proposed for polarimetric remote sensing tailored to ocean applications.The effectiveness of this new feature is validated in three representative ocean observation scenarios,and its performance is compared against both conventional optical feature and DoP feature.The results demonstrate that the AP feature offers distinct advantages in differentiating ocean bodies with varying refractive indices and in emphasizing the differences between observed targets.Moreover,its application enhances the accuracy of unsupervised classification for ocean observations.The establishment of the AP feature greatly strengthens the information-sensing capacity of polarimetric ocean remote sensing,offering a promising pathway to enhance the overall performance of ocean observation systems.展开更多
Originally designed for medical segmentation,the U-Net model excels in ocean remote sensing for segmentation,forecasting,and image enhancement.We propose enhancements like attention mechanisms,knowledge-data integrati...Originally designed for medical segmentation,the U-Net model excels in ocean remote sensing for segmentation,forecasting,and image enhancement.We propose enhancements like attention mechanisms,knowledge-data integration,and diffusion models to improve small target detection,ocean phenomena forecasting,and image super-resolution,expanding U-Net’s application and support in oceanographic research.展开更多
Coastal water environment is essentially enhanced by ocean color which is basically decided by substances concentration in water such as chlorophyll, suspended material and yellow substance. It is very difficult, even...Coastal water environment is essentially enhanced by ocean color which is basically decided by substances concentration in water such as chlorophyll, suspended material and yellow substance. It is very difficult, even not possible, to detect water color by expensive ship routing, because of its temporal and spatial variety of feature and scales in the very complicated dynamical system of coastal water. With the development of satellite technique in the last 20 a, space sensors can be applied to detect ocean color by measuring the spectra of water leaving radiance.It is proven that ocean color remote sensing is a powerful tool for understanding the process of oceanic biology and physics. Since the 1980s, great attention has been paid to the advanced remote sensing technique in China, especially to development of satellite programs for the coastal water environment. On 7 September 1988, China launched her first polar orbit satellite FY-1A for meteorological and oceanographic application (water color and temperature) and the second satellite FY-1B two years later. In May 1999, China launched her second generation environment satellite FY-1C with higher sensitivies, more channels and stable operation. The special ocean color satellite HY-1 is planned to be in the orbit in 2001, whose main purpose is to detect the coastal water environment of China seas. China is also developing a very advantageous sensor termed as Chinese moderate imaging spectra radiometer (CMODIS) with 91 channels, which will be a good candidate of the third generation satellite FY-3 in 2003. The technical system of ocean color remote sensing was developed by the Second Institute of Oceanography (SIO), State Oceanic Administration (SOA) in 1997. The system included data receiving, processing, distribution, calibration, validation and application units. The Hangzhou Station of SIO, SOA has the capability to receive FY-1 and AVHRR data since 1989. It was also a SeaWiFS scientific research station authorized by NASA,USA to free receive SeaWiFS data from 16 September 1997. In the recent years, the local algorithms of atmospheric correction and inversion of ocean color have been developed for FY-1C and SeaWiFS, to improve the accuracy of the measurement from satellites efficiently. The satellite data are being applied to monitor coastal water environment, such as the spatial distribution of chlorophyll, suspended material and yellow substance, red tide detection and coastal current study. The results show that the ocean color remote sensing has latent capacity in the detection of coastal water environment.In consideration of the update technique progress of ocean color remote sensing and its more important role in the detection of coastal water in the 2000s, some suggestions are set forth, which would be beneficial to the design of a cheaper but practical coastal water detection system for marine environment preservation.展开更多
After many years＇ endeavor of research and application practice, the ocean color remote sensing in China has been growing into a new technique with valuable practicality from its initiate stage of trial research. Wit...After many years＇ endeavor of research and application practice, the ocean color remote sensing in China has been growing into a new technique with valuable practicality from its initiate stage of trial research. With the aim of operational service, several kinds of ocean color remote sensing application systems have been developed and realized the long-term marine environmental monitoring utilizing the real-time or near real-time satellite and airborne remote sensing data. New progresses in the technology and application of ocean color remote sensing in China are described, including the research of key techniques and the development of various application systems. Meanwhile, according to the application status and demand, the prospective development of Chinese ocean color remote sensing is brought forward. With Chinese second ocean color satellite （ HY-1 B） orbiting on 11 April 2007 and the development of airborne ocean color remote sensing system for Chinese surveillance planes, great strides will take place in Chinese ocean color remote sensing application with the unique function in marine monitoring, resources management and national security, etc.展开更多
Quantitative analysis and retrieval is given by the State Key Laboratory of Satellite Ocean Environment Dynamics（SOED）,Second Institute of Oceanography（SIO）,State Oceanic Administration（SOA）,China,from the first...Quantitative analysis and retrieval is given by the State Key Laboratory of Satellite Ocean Environment Dynamics（SOED）,Second Institute of Oceanography（SIO）,State Oceanic Administration（SOA）,China,from the first batch of GF-3 synthetic aperture radar（SAR）data with ocean internal wave features in the Yellow Sea.展开更多
This paper demonstrates an atmospheric correction method to process MODIS/Aqua (Moderate-resolution Imaging Spectroradiometer) ocean color imagery over turbid coastal waters with the aid of concurrent CALIOP (Cloud-Ae...This paper demonstrates an atmospheric correction method to process MODIS/Aqua (Moderate-resolution Imaging Spectroradiometer) ocean color imagery over turbid coastal waters with the aid of concurrent CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) aerosol data, assuming that there exists "nonturbid" water in the study area where MODIS aerosol optical properties can be retrieved accurately. Aerosol properties from CALIOP measurements were obtained and related to those from MODIS. This relationship, combined with CALIOP aerosol data, was extended to turbid water to derive MODIS aerosol properties, where atmospheric correction using MODIS data alone often fails. By combining MODIS and CALIOP data, aerosol signals were separated from the total signals at the satellite level, and water-leaving radiances in turbid waters were subsequently derived. This method was tested on several MODIS/Aqua ocean color images over South China turbid waters. Comparison with field data shows that this method was effective in reducing the errors in the retrieved water-leaving radiance values to some extent. In the Zhujiang (Pearl) River Estuary, this method did not overestimate the aerosol effects as severely, and provided far fewer negative water-leaving radiance values than the NASA (National Aeronautics and Space Administration) default methods that used MODIS data alone.展开更多
This paper is divided into three parts.In the first part,it describes the major objects of o-cean monitoring and investigation by means of satellite remote sensing technology,including the observation of dynamic pheno...This paper is divided into three parts.In the first part,it describes the major objects of o-cean monitoring and investigation by means of satellite remote sensing technology,including the observation of dynamic phenomena of ocean,ocean color and sea surface temperature as well as mapping of coastal zone and islands.In the second part,some research results of oceanic environment which were obtained in the past decade in China are presented.In the third part,some fundamental technologies are described,to which we should pay attention in order to make great contribution to marine environment by using satellite remote sensing technology in the coming few years in China.展开更多
Requirements for monitoring the coastal zone environment are first summarized. Then the appli- cation of hyperspectral remote sensing to coast environment investigation is introduced, such as the classification of coa...Requirements for monitoring the coastal zone environment are first summarized. Then the appli- cation of hyperspectral remote sensing to coast environment investigation is introduced, such as the classification of coast beaches and bottom matter, target recognition, mine detection, oil spill identification and ocean color remote sensing. Finally, what is needed to follow on in application of hyperspectral remote sensing to coast environment is recommended.展开更多
Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea （SCS） for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study...Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea （SCS） for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study, the authors investigated the ocean biological and physical responses to typhoon Megi by using chlorophyll-a （chl-a） concentration, sea surface temperature （SST）, sea surface height anomaly （SSHA）, sea surface wind measurements derived from different satellites and in situ data. The chl-a concentration （〉3 mg/m3） increased thirty times in the SCS after the typhoon passage in comparison with the mean level of October averaged from 2002 to 2009. With the relationship of wind stress curl and upwelling, the authors found that the speed of upwelling was over ten times during typhoon than pre-typhoon period. Moreover, the mixed layer deepened about 20 m. These reveal that the enhancement of chl-a concentration was triggered by strong vertical mixing and upwelling. Along the track of typhoon, the maximum sea surface cooling （6-8~C） took place in the SCS where the moving speed of typhoon was only 1.4-2.8 m/s and the mixed layer depth was about 20 m in pre-typhoon period. However, the SST drop at the east of the Philippines is only 1-2~C where the translation speed of typhoon was 5.5-6.9 m/s and the mixed layer depth was about 40 m in pre-typhoon period. So the extent of the SST drop was probably due to the moving speed of typhoon and the depth of the mixed layer. In addition, the region with the largest decline of the sea surface height anomaly can indicate the location where the maximum cooling occurs.展开更多
In 2018,China successfully launched three new Haiyang(which means ocean in Chinese,referred to as HY)satellites which are an ocean color observation satellite HY-1C(operational),an ocean dynamics environment satellite...In 2018,China successfully launched three new Haiyang(which means ocean in Chinese,referred to as HY)satellites which are an ocean color observation satellite HY-1C(operational),an ocean dynamics environment satellite HY-2B(operational)and the China-France ocean satellite CFOSAT(experimental).In 2019,all the three satellites had finished their commissioning phases and were declared operational.HY-2A satellite continues to operate in-orbit,and its operational status is basically normal.So in 2020,China has 4 Haiyang satellites in-orbit,China’s ocean satellites enter into a new operational application phase.The operation of the ground application system of Chinese ocean satellites is stable.In 2019,Beijing,Hainan,Mudanjiang,and Hangzhou ocean satellite ground stations had received the data of HY-1C,HY-2A,HY-2B,and CFOSAT 5012 orbits and 26.46 TB data had been distributed to both domestic and international users.Chinese ocean satellite data has played an important role in marine disaster prevention and mitigation,development and management of marine resources,maintenance of marine rights and interests,marine environment protection,scientific researches,and blue economy development.展开更多
In the present paper, a method is proposed to improve the performance of Artificial Neural Network (ANN) based algorithms for the retrieval of oceanic constituents in Case Ⅱ waters. The ANN-based algorithms have been...In the present paper, a method is proposed to improve the performance of Artificial Neural Network (ANN) based algorithms for the retrieval of oceanic constituents in Case Ⅱ waters. The ANN-based algorithms have been developed based on a constraint condition, which represents, to a certain degree, the correlation between suspended particulate matter (SPM) and pigment (CHL), coloured dissolved organic matter (CDOM) and CHL, as well as CDOM and SPM, found in Case Ⅱ waters. Compared with the ANN-based algorithm developed without a constraint condition, the performance of ANN-based algorithms developed with a constraint conditions is much better for the retrieval of CHL and CDOM, especially in the case of high noise levels; however, there is not significant improvement for the retrieval of SPM.展开更多
Ocean remote sensing satellites provide observations with high spatiotemporal resolution.However,the influence of clouds,fog,and haze frequently leads to significant data gaps.Accurate and effective estimation of thes...Ocean remote sensing satellites provide observations with high spatiotemporal resolution.However,the influence of clouds,fog,and haze frequently leads to significant data gaps.Accurate and effective estimation of these missing data is highly valuable for engineering and scientific research.In this study,the radial basis function(RBF)method is used to estimate the spatial distribution of total suspended matter(TSM)concentration in Hangzhou Bay using remote sensing data with severe data gaps.The estimation precision is validated by comparing the results with those of other commonly used interpolation methods,such as the Kriging method and the basic spline(B-spline)method.In addition,the applicability of the RBF method is explored.Results show that the estimation of the RBF method is significantly close to the observation in Hangzhou Bay.The average of the mean absolute error,mean relative error,and root mean square error in all the experiments is evidently smaller than those of the Kriging and B-spline interpolations,indicating that the proposed method is more appropriate for estimating the spatial distribution of the TSM in Hangzhou Bay.Finally,the TSM distribution in the blank observational area is predicted.This study can provide some reference values for handling watercolor remote sensing data.展开更多
Water clarity(Secchi disk depth, Z_(SD)) and Forel-Ule Index(FUI) are critical ecological indicators for assessing water quality. Although satellite remote sensing serves as a vital tool for large-scale and long-term ...Water clarity(Secchi disk depth, Z_(SD)) and Forel-Ule Index(FUI) are critical ecological indicators for assessing water quality. Although satellite remote sensing serves as a vital tool for large-scale and long-term water quality monitoring,low accuracy, coarse resolution, and incomplete spatial coverage of existing satellite Z_(SD) and FUI products hindered the reliable ecological assessment of water quality. Here, a long-term(2003-2023) satellite dataset of monthly Z_(SD) and FUI was developed by applying the advanced high-accuracy retrieval algorithms and reconstruction method to 35 546Moderate-resolution Imaging Spectroradiometer(MODIS) images over China coastal waters. The new dataset exhibited superior performance compared to the existing one, in terms of higher accuracy(Mean Absolute Percentage Error,MAPE = 28.89% for Z_(SD) and MAPE = 34.46% for FUI), spatio-temporal resolution(monthly, 1 km), and spatial coverage(99.53%), with the most significant improvement found in the nearshore turbid waters. By leveraging this dataset, the ecological impact of human activities on water quality was accurately revealed, as indicated by the significant Z_(SD) improvements during terrestrial pollution control, which was misinterpreted by previous satellite products.Besides, natural factor-induced water quality variability was also successfully captured, particularly the seasonal dynamics of suspended sediment plumes in the East China Sea. The new dataset and adopted methods may provide essential support for the accurate monitoring, ecological assessment, and sustainable management of marine ecosystems.展开更多
An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted ...An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted to get the optimal polarimetric states.The optimization method depresses the power of o-cean clutter and increases the power of ship signal.With the double effects,the contrast of ship to oceanis dramatically increased.Thus small ship or weak signals of low ship-to-ocean power ratio can easily bedetected.Ship signals can be distinguished from speckle noise using the different variation trend after op-timization,and thus the threshold problem can be avoided.Moreover,the analyses of different ship'sKennaugh matrices give two implications.One is that the results are affected little by choosing differentKennaugh matrices of ships with strong intensity from Synthetic Aperture Radar(SAR)images.The otheris that ship's Kennaugh matrix chosen from real SAR images is more favorable than that of ideal scatter-ing.Finally,the optimization results are confirmed by polarimetric scattering angle and co-polarizationphase difference.展开更多
The South China Sea(SCS),situated in southern China,at the junction of the Pacific Plate,the Eurasian Plate,and the Indian Ocean Plate,is a northeast-southwest trending semi-enclosed sea.It spans an area of approximat...The South China Sea(SCS),situated in southern China,at the junction of the Pacific Plate,the Eurasian Plate,and the Indian Ocean Plate,is a northeast-southwest trending semi-enclosed sea.It spans an area of approximately 3.5 million square kilometers and has an average water depth of about 1200 m,its deepest point reaching 5559 m.In 2021,a scientific expedition(called as U1 voyage)in the South China Sea was organized by the Innovation Research Team of Guangdong Special Key Program from March to April,this marks the first comprehensive scientific research voyage to the southern Uboundary corridor.Consisting of a total of 30 papers,this special issue is to share a portion of the research findings from this scientific expedition U1 voyage,covering six aspects:1)characteristics of the marine ecosystem in the SCS and its response to marine dynamic processes;2)multi-scale marine dynamic processes,sea-air interactions,and forecasting techniques in the SCS;3)geomorphology and geological structure;4)sedimentary processes and resource potential in the SCS;5)geostrategy,rights and interests maintenance and strategic countermeasures in the SCS;6)marine scientific instruments.By integrating the scientific research with the study of history,jurisprudence and international strategies,this issue presents new insights into the formation history and scope evolution of the SCS,and it also seeks to establish a new scientific framework based on the marine governance and development of the SCS.展开更多
The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Gener...The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Generally, the water-leaving radiance is high in the turbid water because of the large particle scattering. Based on the in-situ data and ocean color remote sensing data of SeaWiFS, it was found that there was a black water region with the normalized water-leaving radiances less than 0.5 mW/（cm2-μm2-sr）. The optical principle of the occurrence of this black water was analyzed by the inherent optical properties and the ocean color components. The results show that black water is caused by the relative low values of the suspended particle matter concentration and the back scattering ratio. In the black water region, the percentage of the phytoplankton absorption was relatively high, and the large size of the phytoplankton caused the low value of the particle backscattering ratio.展开更多
The large amount of dissolved and particulate material discharged by the Amazon River into the Equatorial Atlantic Ocean cause distinct spectral response of its waters as compared to the nearby ocean waters. This pape...The large amount of dissolved and particulate material discharged by the Amazon River into the Equatorial Atlantic Ocean cause distinct spectral response of its waters as compared to the nearby ocean waters. This paper shows the application of K-means clustering algorithm for classifying water masses in the region under the Amazon River plume influence according to their spectral behavior. Salinity and temperature data from 67 oceanographic stations were related to Sea-viewing Wide Field-of-view Sensor （SeaWiFS） remote sensing reflectances values and the following bio-optical products： （i） chlorophyll-a concentration, （ii） water attenuation coefficient and （iii） absorption coefficient for dissolved and detrital material. Four different water masses were identified such as： （1） oceanic water, （2） intermediate oceanic water, （3） intermediate river plume water and （4） Amazon River plume water. The spectral behavior of these water masses allowed concluding that the main active optical component of the waters in the region is the colored dissolved organic matter originated mostly from the Amazon River.展开更多
In a typical Case-2 coastal water environment(here,the Pearl River Estuary(PRE),China),chromophoric dissolved organic matter(CDOM)and suspended particulates dominate the water optical properties,and CDOM fluorescence ...In a typical Case-2 coastal water environment(here,the Pearl River Estuary(PRE),China),chromophoric dissolved organic matter(CDOM)and suspended particulates dominate the water optical properties,and CDOM fluorescence contributes considerably to surface water reflectance.In this paper,an ultraviolet(UV)to visible scheme to retrieve CDOM absorption(ag)is developed based on a set of in situ observations.First,the CDOM UV absorption and spectral slope(Sg)are derived directly from the visible remote sensing reflectance;then the Sg is extrapolated to obtain the spectrum from UV to visible spectral range.This algorithm performs well,with an overall mean absolute percent difference(MAPD)of^30%,~5%and^6%for the estimation of ag in 250–450 nm,Sg over 250–400 nm,and 250–700 nm,respectively.The effectiveness and stability of the algorithm is further demonstrated in capturing the distribution pattern of CDOM absorption in the PRE from satellite ocean color imagery with multiple spatial and spectral resolution,namely:the Visible Infrared Imaging Radiometer Suite(VIIRS)(750 m/Multispectral),the Ocean and Land Color Instrument(OLCI)(300 m/Multispectral),the Hyperspectral Imager for the Coastal Ocean(HICO)(100 m/Hyperspectral),and the Landsat 8 Operational Land Imager(OLI)(30 m/Multispectral).The UV to visible scheme can benefit the CDOM absorption estimation in two aspects:1)it is free from the disturbance of suspended matter;2)it avoids uncertainties caused by the low signalto-noise ratio(SNR)of ag measurements in the visible range.The algorithm is effective in revealing multiple scales of variation of CDOM absorption from ocean color observations.展开更多
The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uph...The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uphill Battles for Integrated Bohai Sea Management”(UBIBSM,2018–2020)was implemented by the Chinese government.To evaluate the action effectiveness toward water quality improvement,variability of the satelliteobserved water transparency(Secchi disk depth,Z_(SD))was explored,with special emphasis on the nearshore waters(within 20 km from the coastline)prone to terrestrial influence.(1)Compared to the status before the action began(2011–2017),majority(87.3%)of the nearshore waters turned clear during the action implementation period(2018–2020),characterized by the elevated Z_(SD)by 11.6%±12.1%.(2)Nevertheless,the improvement was not spatially uniform,with higher Z_(SD)improvement in provinces of Hebei,Liaoning,and Shandong(13.2%±16.5%,13.2%±11.6%,10.8%±10.2%,respectively)followed by Tianjin(6.2%±4.7%).(3)Bayesian trend analysis found the abrupt Z_(SD)improvement in April 2018,which coincided with the initiation of UBIBSM,implying the water quality response to pollution control.More importantly,the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed Z_(SD)improvement.(4)Compared with previous pollution control actions in the BS,UBIBSM was found to be the most successful one during the past 20 years,in terms of transparency improvement over nearshore waters.The presented results proved the UBIBSM-achieved remarkable water quality improvement,taking the advantage of long-term consistent and objective data record from satellite ocean color observation.展开更多
To acquire high-quality operational data products for Chinese in-orbit and scheduled ocean color sensors, the performances of two operational atmospheric correction(AC) algorithms(ESA MEGS 7.4.1 and NASA Sea DAS 6.1) ...To acquire high-quality operational data products for Chinese in-orbit and scheduled ocean color sensors, the performances of two operational atmospheric correction(AC) algorithms(ESA MEGS 7.4.1 and NASA Sea DAS 6.1) were evaluated over the East China Seas(ECS) using MERIS data. The spectral remote sensing reflectance R_(rs)(λ), aerosol optical thickness(AOT), and ?ngstr?m exponent(α) retrieved using the two algorithms were validated using in situ measurements obtained between May 2002 and October 2009. Match-ups of R_(rs), AOT, and α between the in situ and MERIS data were obtained through strict exclusion criteria. Statistical analysis of R_(rs)(λ) showed a mean percentage difference(MPD) of 9%–13% in the 490–560 nm spectral range, and significant overestimation was observed at 413 nm(MPD>72%). The AOTs were overestimated(MPD>32%), and although the ESA algorithm outperformed the NASA algorithm in the blue-green bands, the situation was reversed in the red-near-infrared bands. The value of α was obviously underestimated by the ESA algorithm(MPD=41%) but not by the NASA algorithm(MPD=35%). To clarify why the NASA algorithm performed better in the retrieval of α, scatter plots of the α single scattering albedo(SSA) density were prepared. These α-SSA density scatter plots showed that the applicability of the aerosol models used by the NASA algorithm over the ECS is better than that used by the ESA algorithm, although neither aerosol model is suitable for the ECS region. The results of this study provide a reference to both data users and data agencies regarding the use of operational data products and the investigation into the improvement of current AC schemes over the ECS.展开更多
基金supported by the National Key R&D Program of China(Grant No.2023YFB3905703)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA19090144)+1 种基金the National Natural Science Foundation of China(Grant No.41842048)the Shenzhen Academician(Expert)Workstation of Orbbec Inc.(XHXS2023-115)。
文摘Optical remote sensing is a crucial component of the ocean observation system.However,the complex interactions between the ocean and atmosphere limit its observation capability and hinder the advancement of quantitative applications and support capacity.Polarimetric remote sensing,as an advanced detection technology,investigates the anisotropic characteristics of electromagnetic waves perpendicular to the direction of propagation.Serving as an extension of conventional optical remote sensing,it significantly improves the accuracy of feature identification and quantitative estimation.As the most classical polarization feature,the Degree of Polarization(DoP)feature has been widely applied in various scenarios.In this study,the spatial distribution of the DoP feature over the 2πobservation space under oceanic conditions is thoroughly investigated through theoretical simulations and sample measurements.Our findings suggest that the DoP feature lacks sufficient sensitivity and versatility to be used independently in ocean observation scenarios.To address this limitation,a novel feature,namely the Angular Polarization(AP)feature,is proposed for polarimetric remote sensing tailored to ocean applications.The effectiveness of this new feature is validated in three representative ocean observation scenarios,and its performance is compared against both conventional optical feature and DoP feature.The results demonstrate that the AP feature offers distinct advantages in differentiating ocean bodies with varying refractive indices and in emphasizing the differences between observed targets.Moreover,its application enhances the accuracy of unsupervised classification for ocean observations.The establishment of the AP feature greatly strengthens the information-sensing capacity of polarimetric ocean remote sensing,offering a promising pathway to enhance the overall performance of ocean observation systems.
基金National Natural Science Foundation of China under grants U2006211,42221005,and 42090044the Strategic Priority Research Program of the Chinese Academy of Sciences under grant XDB42000000.
文摘Originally designed for medical segmentation,the U-Net model excels in ocean remote sensing for segmentation,forecasting,and image enhancement.We propose enhancements like attention mechanisms,knowledge-data integration,and diffusion models to improve small target detection,ocean phenomena forecasting,and image super-resolution,expanding U-Net’s application and support in oceanographic research.
文摘Coastal water environment is essentially enhanced by ocean color which is basically decided by substances concentration in water such as chlorophyll, suspended material and yellow substance. It is very difficult, even not possible, to detect water color by expensive ship routing, because of its temporal and spatial variety of feature and scales in the very complicated dynamical system of coastal water. With the development of satellite technique in the last 20 a, space sensors can be applied to detect ocean color by measuring the spectra of water leaving radiance.It is proven that ocean color remote sensing is a powerful tool for understanding the process of oceanic biology and physics. Since the 1980s, great attention has been paid to the advanced remote sensing technique in China, especially to development of satellite programs for the coastal water environment. On 7 September 1988, China launched her first polar orbit satellite FY-1A for meteorological and oceanographic application (water color and temperature) and the second satellite FY-1B two years later. In May 1999, China launched her second generation environment satellite FY-1C with higher sensitivies, more channels and stable operation. The special ocean color satellite HY-1 is planned to be in the orbit in 2001, whose main purpose is to detect the coastal water environment of China seas. China is also developing a very advantageous sensor termed as Chinese moderate imaging spectra radiometer (CMODIS) with 91 channels, which will be a good candidate of the third generation satellite FY-3 in 2003. The technical system of ocean color remote sensing was developed by the Second Institute of Oceanography (SIO), State Oceanic Administration (SOA) in 1997. The system included data receiving, processing, distribution, calibration, validation and application units. The Hangzhou Station of SIO, SOA has the capability to receive FY-1 and AVHRR data since 1989. It was also a SeaWiFS scientific research station authorized by NASA,USA to free receive SeaWiFS data from 16 September 1997. In the recent years, the local algorithms of atmospheric correction and inversion of ocean color have been developed for FY-1C and SeaWiFS, to improve the accuracy of the measurement from satellites efficiently. The satellite data are being applied to monitor coastal water environment, such as the spatial distribution of chlorophyll, suspended material and yellow substance, red tide detection and coastal current study. The results show that the ocean color remote sensing has latent capacity in the detection of coastal water environment.In consideration of the update technique progress of ocean color remote sensing and its more important role in the detection of coastal water in the 2000s, some suggestions are set forth, which would be beneficial to the design of a cheaper but practical coastal water detection system for marine environment preservation.
基金the National Natural Science Foundation of China under contract Nos 40706061 and 40506036High Tech Research and Development (863) Program of China under contract Nos 2008AA09Z104 and 2007AA12Z137
文摘After many years＇ endeavor of research and application practice, the ocean color remote sensing in China has been growing into a new technique with valuable practicality from its initiate stage of trial research. With the aim of operational service, several kinds of ocean color remote sensing application systems have been developed and realized the long-term marine environmental monitoring utilizing the real-time or near real-time satellite and airborne remote sensing data. New progresses in the technology and application of ocean color remote sensing in China are described, including the research of key techniques and the development of various application systems. Meanwhile, according to the application status and demand, the prospective development of Chinese ocean color remote sensing is brought forward. With Chinese second ocean color satellite （ HY-1 B） orbiting on 11 April 2007 and the development of airborne ocean color remote sensing system for Chinese surveillance planes, great strides will take place in Chinese ocean color remote sensing application with the unique function in marine monitoring, resources management and national security, etc.
基金The National Key R&D Program of China under contract No.2016YFC1401007the National Natural Science Foundation of China under contract Nos 41406203 and 41621064the National High Resolution Project of China under contract No.41-Y20A14-9001-15/16
文摘Quantitative analysis and retrieval is given by the State Key Laboratory of Satellite Ocean Environment Dynamics（SOED）,Second Institute of Oceanography（SIO）,State Oceanic Administration（SOA）,China,from the first batch of GF-3 synthetic aperture radar（SAR）data with ocean internal wave features in the Yellow Sea.
基金Supported by the National Basic Research Program of China (973 Program, Nos. 2009CB723905, 2006CB701300)the National High Technology Research and Development Program of China (863 Program, No. 2007AA12Z161)+3 种基金the NSFC (Nos. 40676094, 40721001, 40706060)MOST, China (No. 2007BAC23B05)Open Fund of Nanchang University (No. Z03975)the Open Fund of Ocean University of China for visiting Ph. D students.
文摘This paper demonstrates an atmospheric correction method to process MODIS/Aqua (Moderate-resolution Imaging Spectroradiometer) ocean color imagery over turbid coastal waters with the aid of concurrent CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) aerosol data, assuming that there exists "nonturbid" water in the study area where MODIS aerosol optical properties can be retrieved accurately. Aerosol properties from CALIOP measurements were obtained and related to those from MODIS. This relationship, combined with CALIOP aerosol data, was extended to turbid water to derive MODIS aerosol properties, where atmospheric correction using MODIS data alone often fails. By combining MODIS and CALIOP data, aerosol signals were separated from the total signals at the satellite level, and water-leaving radiances in turbid waters were subsequently derived. This method was tested on several MODIS/Aqua ocean color images over South China turbid waters. Comparison with field data shows that this method was effective in reducing the errors in the retrieved water-leaving radiance values to some extent. In the Zhujiang (Pearl) River Estuary, this method did not overestimate the aerosol effects as severely, and provided far fewer negative water-leaving radiance values than the NASA (National Aeronautics and Space Administration) default methods that used MODIS data alone.
文摘This paper is divided into three parts.In the first part,it describes the major objects of o-cean monitoring and investigation by means of satellite remote sensing technology,including the observation of dynamic phenomena of ocean,ocean color and sea surface temperature as well as mapping of coastal zone and islands.In the second part,some research results of oceanic environment which were obtained in the past decade in China are presented.In the third part,some fundamental technologies are described,to which we should pay attention in order to make great contribution to marine environment by using satellite remote sensing technology in the coming few years in China.
基金The National "973" Program of China under contract No.2009CB723902the Key Projects of the Knowledge Innovation Program of Chinese Academy of Sciences under contract No.KZCX1-YW-14-2.
文摘Requirements for monitoring the coastal zone environment are first summarized. Then the appli- cation of hyperspectral remote sensing to coast environment investigation is introduced, such as the classification of coast beaches and bottom matter, target recognition, mine detection, oil spill identification and ocean color remote sensing. Finally, what is needed to follow on in application of hyperspectral remote sensing to coast environment is recommended.
基金The National Basic Research Program "973" Program of China under contract No.2009CB421202the National Natural Science Foundation of China under contract Nos 40976110 and 40706061+1 种基金the Public Science and Technology Research Funds Projects of Ocean under contract No.200905012the Zhejiang Provincial Natural Science Foundation of China under contract No.Y5090381
文摘Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea （SCS） for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study, the authors investigated the ocean biological and physical responses to typhoon Megi by using chlorophyll-a （chl-a） concentration, sea surface temperature （SST）, sea surface height anomaly （SSHA）, sea surface wind measurements derived from different satellites and in situ data. The chl-a concentration （〉3 mg/m3） increased thirty times in the SCS after the typhoon passage in comparison with the mean level of October averaged from 2002 to 2009. With the relationship of wind stress curl and upwelling, the authors found that the speed of upwelling was over ten times during typhoon than pre-typhoon period. Moreover, the mixed layer deepened about 20 m. These reveal that the enhancement of chl-a concentration was triggered by strong vertical mixing and upwelling. Along the track of typhoon, the maximum sea surface cooling （6-8~C） took place in the SCS where the moving speed of typhoon was only 1.4-2.8 m/s and the mixed layer depth was about 20 m in pre-typhoon period. However, the SST drop at the east of the Philippines is only 1-2~C where the translation speed of typhoon was 5.5-6.9 m/s and the mixed layer depth was about 40 m in pre-typhoon period. So the extent of the SST drop was probably due to the moving speed of typhoon and the depth of the mixed layer. In addition, the region with the largest decline of the sea surface height anomaly can indicate the location where the maximum cooling occurs.
文摘In 2018,China successfully launched three new Haiyang(which means ocean in Chinese,referred to as HY)satellites which are an ocean color observation satellite HY-1C(operational),an ocean dynamics environment satellite HY-2B(operational)and the China-France ocean satellite CFOSAT(experimental).In 2019,all the three satellites had finished their commissioning phases and were declared operational.HY-2A satellite continues to operate in-orbit,and its operational status is basically normal.So in 2020,China has 4 Haiyang satellites in-orbit,China’s ocean satellites enter into a new operational application phase.The operation of the ground application system of Chinese ocean satellites is stable.In 2019,Beijing,Hainan,Mudanjiang,and Hangzhou ocean satellite ground stations had received the data of HY-1C,HY-2A,HY-2B,and CFOSAT 5012 orbits and 26.46 TB data had been distributed to both domestic and international users.Chinese ocean satellite data has played an important role in marine disaster prevention and mitigation,development and management of marine resources,maintenance of marine rights and interests,marine environment protection,scientific researches,and blue economy development.
文摘In the present paper, a method is proposed to improve the performance of Artificial Neural Network (ANN) based algorithms for the retrieval of oceanic constituents in Case Ⅱ waters. The ANN-based algorithms have been developed based on a constraint condition, which represents, to a certain degree, the correlation between suspended particulate matter (SPM) and pigment (CHL), coloured dissolved organic matter (CDOM) and CHL, as well as CDOM and SPM, found in Case Ⅱ waters. Compared with the ANN-based algorithm developed without a constraint condition, the performance of ANN-based algorithms developed with a constraint conditions is much better for the retrieval of CHL and CDOM, especially in the case of high noise levels; however, there is not significant improvement for the retrieval of SPM.
基金supported by the Open Funds for Hubei Key Laboratory of Marine Geological Resources,China University of Geosciences(No.MGR202308)the Natural Science Foundation of Shandong Province(No.ZR2020MD085)+3 种基金the National Natural Science Foundation of China(No.41821004)the Taishan Scholar Program(No.tstp2022114)the Shandong Provincial Natural Science Foundation(No.DKXZZ202206)the National Key Research and Development Program of China(No.2016YFC1402404).
文摘Ocean remote sensing satellites provide observations with high spatiotemporal resolution.However,the influence of clouds,fog,and haze frequently leads to significant data gaps.Accurate and effective estimation of these missing data is highly valuable for engineering and scientific research.In this study,the radial basis function(RBF)method is used to estimate the spatial distribution of total suspended matter(TSM)concentration in Hangzhou Bay using remote sensing data with severe data gaps.The estimation precision is validated by comparing the results with those of other commonly used interpolation methods,such as the Kriging method and the basic spline(B-spline)method.In addition,the applicability of the RBF method is explored.Results show that the estimation of the RBF method is significantly close to the observation in Hangzhou Bay.The average of the mean absolute error,mean relative error,and root mean square error in all the experiments is evidently smaller than those of the Kriging and B-spline interpolations,indicating that the proposed method is more appropriate for estimating the spatial distribution of the TSM in Hangzhou Bay.Finally,the TSM distribution in the blank observational area is predicted.This study can provide some reference values for handling watercolor remote sensing data.
基金The National Key Research and Development Program of China under contract No.2023YFB3905305。
文摘Water clarity(Secchi disk depth, Z_(SD)) and Forel-Ule Index(FUI) are critical ecological indicators for assessing water quality. Although satellite remote sensing serves as a vital tool for large-scale and long-term water quality monitoring,low accuracy, coarse resolution, and incomplete spatial coverage of existing satellite Z_(SD) and FUI products hindered the reliable ecological assessment of water quality. Here, a long-term(2003-2023) satellite dataset of monthly Z_(SD) and FUI was developed by applying the advanced high-accuracy retrieval algorithms and reconstruction method to 35 546Moderate-resolution Imaging Spectroradiometer(MODIS) images over China coastal waters. The new dataset exhibited superior performance compared to the existing one, in terms of higher accuracy(Mean Absolute Percentage Error,MAPE = 28.89% for Z_(SD) and MAPE = 34.46% for FUI), spatio-temporal resolution(monthly, 1 km), and spatial coverage(99.53%), with the most significant improvement found in the nearshore turbid waters. By leveraging this dataset, the ecological impact of human activities on water quality was accurately revealed, as indicated by the significant Z_(SD) improvements during terrestrial pollution control, which was misinterpreted by previous satellite products.Besides, natural factor-induced water quality variability was also successfully captured, particularly the seasonal dynamics of suspended sediment plumes in the East China Sea. The new dataset and adopted methods may provide essential support for the accurate monitoring, ecological assessment, and sustainable management of marine ecosystems.
基金the High Technology Research and Development Programme of China(No.2002AA633120)Sharing and Opening Projects of ENVISAT ASAR Data
文摘An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted to get the optimal polarimetric states.The optimization method depresses the power of o-cean clutter and increases the power of ship signal.With the double effects,the contrast of ship to oceanis dramatically increased.Thus small ship or weak signals of low ship-to-ocean power ratio can easily bedetected.Ship signals can be distinguished from speckle noise using the different variation trend after op-timization,and thus the threshold problem can be avoided.Moreover,the analyses of different ship'sKennaugh matrices give two implications.One is that the results are affected little by choosing differentKennaugh matrices of ships with strong intensity from Synthetic Aperture Radar(SAR)images.The otheris that ship's Kennaugh matrix chosen from real SAR images is more favorable than that of ideal scatter-ing.Finally,the optimization results are confirmed by polarimetric scattering angle and co-polarizationphase difference.
基金Supported by the Guangdong Special Key Team Program(No.2019BT02H594)the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2021GD0810)the Major Project of National Social Science Foundation of China(No.21ZDA097)(Research on the Active Participation in the Reform of Global Economic Governance System)。
文摘The South China Sea(SCS),situated in southern China,at the junction of the Pacific Plate,the Eurasian Plate,and the Indian Ocean Plate,is a northeast-southwest trending semi-enclosed sea.It spans an area of approximately 3.5 million square kilometers and has an average water depth of about 1200 m,its deepest point reaching 5559 m.In 2021,a scientific expedition(called as U1 voyage)in the South China Sea was organized by the Innovation Research Team of Guangdong Special Key Program from March to April,this marks the first comprehensive scientific research voyage to the southern Uboundary corridor.Consisting of a total of 30 papers,this special issue is to share a portion of the research findings from this scientific expedition U1 voyage,covering six aspects:1)characteristics of the marine ecosystem in the SCS and its response to marine dynamic processes;2)multi-scale marine dynamic processes,sea-air interactions,and forecasting techniques in the SCS;3)geomorphology and geological structure;4)sedimentary processes and resource potential in the SCS;5)geostrategy,rights and interests maintenance and strategic countermeasures in the SCS;6)marine scientific instruments.By integrating the scientific research with the study of history,jurisprudence and international strategies,this issue presents new insights into the formation history and scope evolution of the SCS,and it also seeks to establish a new scientific framework based on the marine governance and development of the SCS.
基金The National Basic Research and Development Program ("973" Program) of China under contract No2009CB421202the National Natural Science Foundation of China under contract No 40706061the National High Technol-ogy Development Program ("863" Program) of China under contract Nos 2007AA12Z137 and 2008AA09Z104
文摘The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Generally, the water-leaving radiance is high in the turbid water because of the large particle scattering. Based on the in-situ data and ocean color remote sensing data of SeaWiFS, it was found that there was a black water region with the normalized water-leaving radiances less than 0.5 mW/（cm2-μm2-sr）. The optical principle of the occurrence of this black water was analyzed by the inherent optical properties and the ocean color components. The results show that black water is caused by the relative low values of the suspended particle matter concentration and the back scattering ratio. In the black water region, the percentage of the phytoplankton absorption was relatively high, and the large size of the phytoplankton caused the low value of the particle backscattering ratio.
文摘The large amount of dissolved and particulate material discharged by the Amazon River into the Equatorial Atlantic Ocean cause distinct spectral response of its waters as compared to the nearby ocean waters. This paper shows the application of K-means clustering algorithm for classifying water masses in the region under the Amazon River plume influence according to their spectral behavior. Salinity and temperature data from 67 oceanographic stations were related to Sea-viewing Wide Field-of-view Sensor （SeaWiFS） remote sensing reflectances values and the following bio-optical products： （i） chlorophyll-a concentration, （ii） water attenuation coefficient and （iii） absorption coefficient for dissolved and detrital material. Four different water masses were identified such as： （1） oceanic water, （2） intermediate oceanic water, （3） intermediate river plume water and （4） Amazon River plume water. The spectral behavior of these water masses allowed concluding that the main active optical component of the waters in the region is the colored dissolved organic matter originated mostly from the Amazon River.
基金This work was supported by the National Natural Science Foundation of China(Grant No.41376035)the General Research Fund of Hong Kong Research Grants Council(RGC)(Nos.CUHK 14303818,402912,and 403113)the Hong Kong Innovation and Technology Fund(Nos.ITS/259/12 and ITS/321/13).
文摘In a typical Case-2 coastal water environment(here,the Pearl River Estuary(PRE),China),chromophoric dissolved organic matter(CDOM)and suspended particulates dominate the water optical properties,and CDOM fluorescence contributes considerably to surface water reflectance.In this paper,an ultraviolet(UV)to visible scheme to retrieve CDOM absorption(ag)is developed based on a set of in situ observations.First,the CDOM UV absorption and spectral slope(Sg)are derived directly from the visible remote sensing reflectance;then the Sg is extrapolated to obtain the spectrum from UV to visible spectral range.This algorithm performs well,with an overall mean absolute percent difference(MAPD)of^30%,~5%and^6%for the estimation of ag in 250–450 nm,Sg over 250–400 nm,and 250–700 nm,respectively.The effectiveness and stability of the algorithm is further demonstrated in capturing the distribution pattern of CDOM absorption in the PRE from satellite ocean color imagery with multiple spatial and spectral resolution,namely:the Visible Infrared Imaging Radiometer Suite(VIIRS)(750 m/Multispectral),the Ocean and Land Color Instrument(OLCI)(300 m/Multispectral),the Hyperspectral Imager for the Coastal Ocean(HICO)(100 m/Hyperspectral),and the Landsat 8 Operational Land Imager(OLI)(30 m/Multispectral).The UV to visible scheme can benefit the CDOM absorption estimation in two aspects:1)it is free from the disturbance of suspended matter;2)it avoids uncertainties caused by the low signalto-noise ratio(SNR)of ag measurements in the visible range.The algorithm is effective in revealing multiple scales of variation of CDOM absorption from ocean color observations.
基金The fund supported by Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) under contract No. SML2021SP313the fundamental research funds for the Central Universities of Sun Yat-Sen University under contract No.23xkjc019the fund supported by China-Korea Joint Ocean Research Center of China under contract No. PI-2022-1-01
文摘The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uphill Battles for Integrated Bohai Sea Management”(UBIBSM,2018–2020)was implemented by the Chinese government.To evaluate the action effectiveness toward water quality improvement,variability of the satelliteobserved water transparency(Secchi disk depth,Z_(SD))was explored,with special emphasis on the nearshore waters(within 20 km from the coastline)prone to terrestrial influence.(1)Compared to the status before the action began(2011–2017),majority(87.3%)of the nearshore waters turned clear during the action implementation period(2018–2020),characterized by the elevated Z_(SD)by 11.6%±12.1%.(2)Nevertheless,the improvement was not spatially uniform,with higher Z_(SD)improvement in provinces of Hebei,Liaoning,and Shandong(13.2%±16.5%,13.2%±11.6%,10.8%±10.2%,respectively)followed by Tianjin(6.2%±4.7%).(3)Bayesian trend analysis found the abrupt Z_(SD)improvement in April 2018,which coincided with the initiation of UBIBSM,implying the water quality response to pollution control.More importantly,the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed Z_(SD)improvement.(4)Compared with previous pollution control actions in the BS,UBIBSM was found to be the most successful one during the past 20 years,in terms of transparency improvement over nearshore waters.The presented results proved the UBIBSM-achieved remarkable water quality improvement,taking the advantage of long-term consistent and objective data record from satellite ocean color observation.
基金Supported by the State Key Program of National Natural Science Foundation of China(No.60638020)the State Scholarship Fund of the China Scholarship Council(CSC)+1 种基金the National Natural Science Foundation of China(Nos.41321004,41276028,41206006,41306192,41306035)the Natural Science Foundation of Zhejiang Province(No.LY15D060001)
文摘To acquire high-quality operational data products for Chinese in-orbit and scheduled ocean color sensors, the performances of two operational atmospheric correction(AC) algorithms(ESA MEGS 7.4.1 and NASA Sea DAS 6.1) were evaluated over the East China Seas(ECS) using MERIS data. The spectral remote sensing reflectance R_(rs)(λ), aerosol optical thickness(AOT), and ?ngstr?m exponent(α) retrieved using the two algorithms were validated using in situ measurements obtained between May 2002 and October 2009. Match-ups of R_(rs), AOT, and α between the in situ and MERIS data were obtained through strict exclusion criteria. Statistical analysis of R_(rs)(λ) showed a mean percentage difference(MPD) of 9%–13% in the 490–560 nm spectral range, and significant overestimation was observed at 413 nm(MPD>72%). The AOTs were overestimated(MPD>32%), and although the ESA algorithm outperformed the NASA algorithm in the blue-green bands, the situation was reversed in the red-near-infrared bands. The value of α was obviously underestimated by the ESA algorithm(MPD=41%) but not by the NASA algorithm(MPD=35%). To clarify why the NASA algorithm performed better in the retrieval of α, scatter plots of the α single scattering albedo(SSA) density were prepared. These α-SSA density scatter plots showed that the applicability of the aerosol models used by the NASA algorithm over the ECS is better than that used by the ESA algorithm, although neither aerosol model is suitable for the ECS region. The results of this study provide a reference to both data users and data agencies regarding the use of operational data products and the investigation into the improvement of current AC schemes over the ECS.
