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1.
遥感水深反演具有非接触测量和省时省力等优点,能够为航海、岛礁工程与珊瑚礁生态调查等活动提供重要参考。随着高光谱遥感卫星数量的增长,基于高光谱遥感影像的水深反演具有良好的发展与应用潜力。HOPE（Hyperspectral Optimization Process Exemplar）算法是比较常用的高光谱水深反演算法。鉴于HOPE算法在低遥感反射率海域会出现水深被高估的问题,本文基于Hyperion高光谱遥感影像提出一种改进的水深反演算法。该算法针对危险或难以到达海域往往具有水体光学性质较为均一的特点,利用深水区遥感反射率的观测值来估计整个研究区域内的水体光学性质参数并将其固定,以便减少未知参数数量,解决水深被高估的问题,最终达到提高水深反演整体精度的目的。塞班岛和中业岛的实验结果表明,改进算法能够有效克服常规HOPE算法在低遥感反射率水域高估水深的问题。改进算法能够将平均遥感反射率小于0.0075sr-1（塞班岛）和0.001 sr-1（中业岛）范围内的水域的水深反演平均绝对误差从常规HOPE算法的2.94 m和6.44 m分别降低至2.56 m和4.99 m,从而能够相应地将整体的均方根误差从3.18 m和5.39 m分别降低至2.30 m和3.32 m,而将整体的平均相对误差从32.4%和27.1%分别降低至30.6%和23.9%。因此,改进算法在提高卫星高光谱遥感影像水深反演效果方面具有可行性和有效性。  相似文献   

2.
THE NOMENCLATURE OF THE SOUTH CHINA SEA ISLANDS IN ANCIENT CHINA   总被引：1，自引：0，他引：1  
ＴＨＥＮＯＭＥＮＣＬＡＴＵＲＥＯＦＴＨＥＳＯＵＴＨＣＨＩＮＡＳＥＡＩＳＬＡＮＤＳＩＮＡＮＣＩＥＮＴＣＨＩＮＡ￥ＬｉｕＮａｎｗｅｉ（刘南威）（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｇｒａｐｈｙ，ＳｏｕｔｈＣｈｉｎａＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｇｕａｎｇｚ...  相似文献   

3.
吴柯  杨帆  徐莹 《地质科技通报》2022,41(5):181-189
近年来, 受人类活动和全球变暖的双重影响, 我国南海区域珊瑚礁生态系统退化, 发生白化现象。利用遥感技术监测和掌握珊瑚礁的白化情况, 对南海生态环境的保护和治理具有重大价值。首先通过多期海表温度数据获取珊瑚礁白化预警的区域, 选定西沙群岛永乐环礁中的羚羊礁作为研究对象; 然后, 提出了一种新型的珊瑚礁白化监测模型, 分别采取水深校正、珊瑚礁分类、反射率调整以及阈值选择等方式对2013-2018年的Landsat-8遥感影像开展了多时间序列的珊瑚礁白化监测研究。最终的结果显示, 该模型能够较为准确地获取珊瑚礁白化区域, 为南海珊瑚礁白化现象的长时间序列监测提供依据。   相似文献   

4.
面向对象的南海珊瑚礁地貌单元提取   总被引：3，自引：0，他引：3  
南海珊瑚礁地貌信息的提取是珊瑚礁资源利用、生态保护与管理及可持续发展的重要地学基础。本文提出了面向对象的珊瑚礁地貌单元提取模型,针对不同的地貌单元,以不同地貌单元的最优分割尺度、光谱参数、形状参数来分割影像并合并成不同对象,从而获得相应的地貌单元。通过大量实验得出自然地貌的最优分割尺度区间为[140,600],其中附礁生物稀疏带及丛生带、礁坑发育带的光谱参数和形状参数分别为0.9和0.1,其他自然地貌单元的光谱参数和形状参数分别为0.8和0.2;人工地貌的最优分割尺度区间为[25,170],其光谱参数和形状参数分别为0.8和0.2。进一步以南沙群岛簸箕礁WorldView-2高分辨率遥感影像为例提取地貌单元,并结合混淆矩阵和Kappa系数对分类结果进行了精度评价,地貌单元提取总体精度达到了85.75%,Kappa系数为0.8349。结果表明,该方法可有效运用南海珊瑚礁遥感影像的光谱特征、纹理特征,以及影像数据不同波段的组合特性,综合了影像和珊瑚礁地貌的关联特性,充分利用了珊瑚礁不同地貌相带的异质性,获得了理想的南海珊瑚礁地貌的整体信息,满足了我国南海珊瑚礁地貌信息提取和地貌数字产品生成的需求。  相似文献   

5.
Study of the distribution and migration of the common squid,Todarodes pacificus Steenstrup,basedon the index of important fishing ground(P) and fisheries statistics on the Yellow Sea and northern EastChina Sea during 1980—1991 showed that:1.Its catch in the fishing period(June to November) is 91.77% of the annual yield.The fishingground distributes over the northem and middle Yel1ow Sea and adjacent area of the Changjiang Estuary.2. It over-winters in the northem East China Sea and waters adjacent to Goto Island from De-cember to February and spawns in waters near Haijiao Is1and and west of Kyushu. The main stock mi-grates along 123°30′E to the ChangJiang Estuary, Haizhou Bay. offsea from Shidao to Qingdao,mideastern Yellow Sea, and offsea Weihai and Haiyang Island succesively for feeding after April. The sur-plus stock migrates again to the wintering ground in December.3.The favorable feeding temperature is 6-23℃(optimum of l3-20℃ in the Changjiang Estua-ry and 7-13℃ in the northern and middle Yel  相似文献   

6.
Coral reefs in the Xisha Islands(also known as the Paracel Islands in English), South China Sea, have experienced dramatic declines in coral cover. However, the current regional scale hard coral distribution of geomorphic and ecological zones, essential for reefs management in the context of global warming and ocean acidification, is not well documented. We analyzed data from field surveys, Landsat-8 and GF-1 images to map the distribution of hard coral within geomorphic zones and reef flat ecological zones. In situ surveys conducted in June 2014 on nine reefs provided a complete picture of reef status with regard to live coral diversity, evenness of coral cover and reef health(live versus dead cover) for the Xisha Islands. Mean coral cover was 12.5% in 2014 and damaged reefs seemed to show signs of recovery. Coral cover in sheltered habitats such as lagoon patch reefs and biotic dense zones of reef flats was higher, but there were large regional differences and low diversity. In contrast, the more exposed reef slopes had high coral diversity, along with high and more equal distributions of coral cover. Mean hard coral cover of other zones was 10%. The total Xisha reef system was estimated to cover 1 060 km~2, and the emergent reefs covered ~787 km~2. Hard corals of emergent reefs were considered to cover 97 km~2. The biotic dense zone of the reef flat was a very common zone on all simple atolls, especially the broader northern reef flats. The total cover of live and dead coral can reach above 70% in this zone, showing an equilibrium between live and dead coral as opposed to coral and algae. This information regarding the spatial distribution of hard coral can support and inform the management of Xisha reef ecosystems.  相似文献   

7.
We propose a bio-optical inversion model that retrieves the absorption contributions of phytoplankton and colored detrital matter(CDM),as well as the phytoplankton size classes(PSCs),from total minus water absorption spectra.The model is based on three-component separation of phytoplankton size structure and a genetic algorithm.The model performance was tested on two independent datasets(the NASA bio-Optical Marine Algorithm Dataset(NOMAD) and the northern South China Sea(NSCS) dataset).The relationships between the estimated and measured values were strongly linear,especially for aCDM(412),and the Root Mean Square Error(RMSE) of the CDM exponential slope(SCDM) was relatively low.Next,the inversion model was directly applied to in-situ total minus water absorption spectra determined by an underwater meter during a cruise in September 2008,to retrieve the phytoplankton size structure in the seawater.By comparing the measured and retrieved chlorophyll a concentrations,we demonstrated that total and size-specific chlorophyll a concentrations could be retrieved by the model with relatively high accuracy.Finally,we applied the bio-optical inversion model to investigate changes in phytoplankton size structure induced by an anti-cyclonic eddy in the NSCS.  相似文献   

8.
The Andaman and Nicobar Islands are one of the Union Territories of India, located in the eastern part of the Bay of Bengal. In 2010 summer, the increment in sea surface water temperature (up to 34℃) resulted in the bleaching of about 74% to 77% of corals in the South Andaman. During this event, coral species such as Acropora cerealis, A. humilis, Montipora sp., Favia pallida, Diploastrea sp., Goniopora sp. Fungia concinna, Gardineroseries sp., Porites sp., Favites abdita and Lobophyllia robusta were severely affected. This study is to assess the recovery status of the reef ecosystem by estimating the percentage of Live Coral cover, Bleached coral cover, Dead coral with algae, Rubble, Sandy flat, Algal assemblage and other associated organisms. The sedimentation rate (mg cm-2 d-1) and coral coverage (%) were assessed during this study period. The average sedimentation rate was ranged between 0.27 and 0.89 mg cm-2 d-1 . The observed post bleaching recovery of coral cover was 21.1% at Port Blair Bay and 13.29% at Havelock Island. The mortality rate of coral cover due to this bleaching was estimated as 2.05% at Port Blair Bay and 9.82% at Havelock Island. Once the sea water temperature resumed back to the normal condition, most of the corals were found recovered.  相似文献   

9.
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(MPD72%). The AOTs were overestimated(MPD32%), 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.  相似文献   

10.
Remote sensing technique, replacing conventional sonar bathymetry technique, has become an effective complementary method of mapping submarine terrain where special conditions make the sonar technique difficult to be carried out. At the same time, as one kind of data set, multispectral remote sensing data has the disadvantage of being influenced by the variable bottom types in shallow seawater, when it is applied in bathymetry. This paper puts forward a new method to extract water depth information fi‘om multispectral data, considering the bottom classification and the true water depth accuracy. That is the Principal Component Analysis (PCA) technique based on the bottom classification. By the least square regression with significance, the experiment near Qingdao City has obtained more satisfactory bathymetry accuracy than that of the traditional single-band method, with the mean absolute error about 2.57m.  相似文献   

11.
Although remote sensing data have been used to estimate total suspended matter (TSM) in coastal waters, it has limitations when applied to estuary waters in low spatial resolution situations. The spatial resolution of ocean color satellites such as SeaWiFS and MODIS is usually ～1 km, and therefore is not adequate for small, local-scale areas such as the Zhujiang (Pearl) River estuary. In contrast, 30 m-resolution EO-1 Hyperion imagery has potential for studying TSM in localized areas. We measured the surface spectral radiance reflectance of the river estuary water in the visible and near infra-red spectral range. Sensitivity analysis indicated that the ratio of remote sensing reflectance at 813 nm (Rrs(813)) to reflectance at 559 nm (Rrs(559)) could be used to estimate TSM concentration, and a linear relationship was established between the ratio and in-situ TSM concentration. We applied the linear relationship to Hyperion imagery to map TSM concentration in the estuary. The Hyperion imagery provided sufficient spatial resolution to detect spatiotemporal changes in TSM concentrations in the estuary small estuary area. This study demonstrated the usefulness of Hyperion imagery for mapping the distribution of TSM in estuary waters.  相似文献   

12.
A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea), are newly identified based on the sea-surface temperature from satellite remote sensing, and further confirmed by the distribution of suspended sediments. In addition, there are two obvious thermal fronts associated with the onshore warm tongue and off shore cold tongue. The narrow gap between the two thermal fronts is supposed to be the pathway for the off shore transport of cold coastal water and suspended sediments. The concurrence of onshore warm and of fshore cold tongues suggests the concurrence of onshore and off shore currents in the western Yellow Sea in winter, which seems to be inconsistent with the previously accepted view that, in winter, the Yellow Sea Coastal Current flows from the Old Huanghe Delta to the southwest of Jeju Island. This distinctive phenomenon helps establish an updated view of the circulation in the western Yellow Sea in winter.  相似文献   

13.
A new species of goneplacid crab, Paragoneplax chenae, is described, based on collections from the Nansha Islands, South China Sea. P. chenae closely resembles its only congener P. serenei (Zarenkov, 1972) in general appearance. They are distinguishable from each other by the male abdominal and gonopodal characters.  相似文献   

14.
In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka,the vertical gradient of δ 13 C in dissolved inorganic carbon(δ 13 C between those of foraminifera Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi) and planktonic foraminiferal assemblages were analysed in piston Core MD06-3047 retrieved from the Benham Rise(east of the Luzon Island).Paleoproductivity evolution in the West Philippine Sea during the last 700 ka is closely related to glacial-interglacial cycles and precession-controlled insolation.Controlling factors of paleoproductivity could have been both thermocline fluctuations related with ENSO-like processes and eolian input associated with East Asian winter monsoon,and the former could have been the primary factor.A higher productivity and a shallower thermocline coeval with the occurrence of low CO 2 concentrations in the EPICA Dome C ice core might indicate that biological export production in the low-latitude could act as a significant sink in the global carbon cycle,and modify atmospheric CO 2 concentrations.Spectral analysis further reveals that the paleoproductivity is mainly controlled by thermocline fluctuations subjected to ENSO processes responding to processional variability of insolation.High coherences in eccentricity,obliquity and precession periods further revealing the close link between thermocline fluctuations,paleoproductivity and atmospheric CO 2 levels.  相似文献   

15.
Internal waves can bring nutrients to the upper level of water bodies and facilitate phytoplankton photosynthesis. Internal waves occur frequently in the northern portion of the South China Sea and inflict an important effect on chlorophyll a distribution. In this study, in-situ observation and satellite remote sensing data were used to study the effects of internal waves on chlorophyll a distribution. Based on the in-situ observations, lower chlorophyll a concentrations were present in the middle and bottom level in areas in which internal waves occur frequently, while the surface chlorophyll a distribution increased irregularly, and a small area with relatively higher chlorophyll a concentrations was observed in the area around the Dongsha Island. Satellite remote sensing showed that the chlorophyll a concentration increased in the area near Dongsha Island, where internal waves frequently occurred. The results of the increased chlorophyll a concentration in the surface water near Dongsha Island in the northern portion of the South China Sea indicated that internal waves could uplift phytoplankton and facilitate phytoplankton growth.  相似文献   

16.
In recent years, infrastructure construction on coral reefs has been increasingly developed. Therefore, the shallow strata stability of coral reefs in the South China Sea should be evaluated. This study aims to investigate the profiles for the shallow strata of coral reefs in the southwest of the Yongshu Reef, particularly in the hydrodynamic marine environment, and to establish a geological model for numerical simulation using Geo-Studio. The shallow strata of the coral reefs include mass gravel, sand gravel, mid-coarse sand, silty sand, fine sand, and reef limestone. The shallow reef slope near the lagoon is similar to a ‘layer cake', in which the side close to the sea is analogous to a ‘block cake'. The simulation results showed that coral reef stability depends on wave loads and earthquake strength and on the physical properties of coral reefs. The factor of safety for the outer reef is greater than 10.0 under static, wave, and seismic conditions; this indicated that the outer reefs were less affected by waves and earthquakes. However, the factor of safety next to the lagoon varied from 0.1 to 5.3. The variation was primarily caused by the thick strata of coral reefs close to the sea(reef limestone, typically with the thickness 10 m and equivalent to a block). The soil and rock layers in the coral reef strata with thicknesses 10 m showed weak engineering geological characteristics. Our findings can provide useful information to future construction projects on coral reefs.  相似文献   

17.
A new ocean wave and sea surface current monitoring system with horizontally-(HH) and vertically-(VV) polarized X-band radar was developed. Two experiments into the use of the radar system were carried out at two sites, respectively, for calibration process in Zhangzi Island of the Yellow Sea, and for validation in the Yellow Sea and South China Sea. Ocean wave parameters and sea surface current velocities were retrieved from the dual polarized radar image sequences based on an inverse method. The results obtained from dual-polarized radar data sets acquired in Zhangzi Island are compared with those from an ocean directional buoy. The results show that ocean wave parameters and sea surface current velocities retrieved from radar image sets are in a good agreement with those observed by the buoy. In particular, it has been found that the vertically-polarized radar is better than the horizontally-polarized radar in retrieving ocean wave parameters, especially in detecting the significant wave height below 1.0 m.  相似文献   

18.
We studied diatom distribution from 62 samples from the uppermost 1 cm of sediment in the South China Sea (SCS), using grabs or box corers in three cruises between 2001–2007. Fifty six genera, 256 species and their varieties were identified. Dominating species included Coscinodiscus africanus, Coscinodiscus nodulifer, Cyclotella stylorum, Hemidiscus cuneiformis, Melosira sulcata, Nitzschia marina, Roperia tesselata, Thalassionema nitzschioides, Thalassiosira excentrica, and Thalassiothrix longissima. Most surface sediments in the SCS were rich in diatoms, except for a few coarse samples. Average diatom abundance in the study area was 104 607 valve/g. In terms of the abundance, ecology, and spatial distribution, seven diatom zones (Zones 1–7) were recognized. Zone 1 (northern continental shelf) is affected by warm currents, SCS northern branch of the Kuroshio, and northern coastal currents; Zone 2 (northwestern continental shelf) is affected by intense coastal currents; Zone 3 (Xisha Islands sea area) is a bathyal environment with transitional water masses; Zone 4 (sea basin) is a bathyal-to-deep sea with stable and uniform central water masses in a semi-enclosed marginal sea; Zone 5 (Nansha Islands marine area) is a pelagic environment with relatively high surface temperature; Zone 6 (northern Sunda Shelf) is a tropical shelf environment; and Zone 7 (northern Kalimantan Island shelf area) is affected by warm waters from the Indian Ocean and coastal waters. The data indicate that these diatom zones are closely related to topography, hydrodynamics, temperature, nutrients and especially the salinity. Better understanding of the relationship between diatom distribution and the oceanographic factors would help in the reconstruction of the SCS in the past.  相似文献   

19.
Every year during late spring and summer, a patch of surface cold water exists near the eastern side of the Subei shoal patch. The main cause of the cold water is the monthly southward migration and climbing up of the deep cold water from the western part of the southern Huanghai Sea. The existence of the deep ditches on the north side of the underwater delta off Subei controls the position of this cold water. Another patch of cold water is commonly observed southwest of Jizhou Island on the surface in the region 32oN and 124o–124.5oE during late spring and summer. Based on analysis, this water comes mainly from the deep layers of the northwest area; its upwelling is related to the northward “impulsive” extension of the Taiwan Warm Current in the previous period, and its position is probably related to the underwater reef chain there.  相似文献   

20.
The sea surface salinity(SSS) is a key parameter in monitoring ocean states. Observing SSS can promote the understanding of global water cycle. This paper provides a new approach for retrieving sea surface salinity from Soil Moisture and Ocean Salinity(SMOS) satellite data. Based on the principal component regression(PCR) model, SSS can also be retrieved from the brightness temperature data of SMOS L2 measurements and Auxiliary data. 26 pair matchup data is used in model validation for the South China Sea(in the area of 4?–25?N, 105?–125?E). The RMSE value of PCR model retrieved SSS reaches 0.37 psu(practical salinity units) and the RMSE of SMOS SSS1 is 1.65 psu when compared with in-situ SSS. The corresponding Argo daily salinity data during April to June 2013 is also used in our validation with RMSE value 0.46 psu compared to 1.82 psu for daily averaged SMOS L2 products. This indicates that the PCR model is valid and may provide us with a good approach for retrieving SSS from SMOS satellite data.  相似文献   

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