Institutional Repository of South China Sea Institute of Oceanology, CAS
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Multiple Time Scale Variability of the Sea Surface Salinity Dipole Mode in the Tropical Indian Ocean
No full textIn this study, multiple time scale variability of the salinity dipole mode in the tropical Indian Ocean (S-IOD) is revealed based on the 57-yr Ocean Reanalysis System 4 (ORAS4) sea surface salinity (SSS) reanalysis product and associated observations. On the interannual time scale, S-IOD is highly correlated with strong Indian Ocean dipole (IOD) and ENSO variability, with ocean advection forced by wind anomalies along the equator and precipitation anomalies in the southeastern tropical Indian Ocean (IO) dominating the SSS variations in the northern and southern poles of the S-IOD, respectively. S-IOD variability is also associated with the decadal modulation of the Indo-Pacific Walker circulation, with a stronger signature at its southern pole. Decadal variations of the equatorial IO winds and precipitations in the central IO force zonal ocean advection anomalies that contribute to the SSS variability in the northern pole of S-IOD on the decadal time scale. Meanwhile, oceanic dynamics dominates the SSS variability in the southern pole of S-IOD off Western Australia. Anomalous ocean advection transports the fresher water from low latitudes to the region off Western Australia, with additional contributions from the Indonesian Throughflow. Furthermore, the southern pole of S-IOD is associated with the thermocline variability originated from the tropical northwestern Pacific through the waveguide in the Indonesian Seas, forced by decadal Pacific climate variability. A deepening (shoaling) thermocline strengthens (weakens) the southward advection of surface freshwater into the southern pole of S-IOD and contributes to the high (low) SSS signatures off Western Australia
Assessment of tropical cyclone disaster loss in Guangdong Province based on combined model
No full textTropical cyclone (TC) disaster loss assessment is an important and difficult problem in TC prevention and disaster mitigation. Few studies have focused on combined model in this area. This study introduced a new combination model method to predict TC disaster loss, taking Guangdong province as an example. We analysed and collected 67 TC data from 1993 to 2009, which had impact on Guangdong province, in which 60 were randomly for training data and another 7 were for testing data. We conducted three models - GA-Elman neural networks, support vector regression (SVR) and generalized regression neural networks (GRNN), and the root mean square error (RMSE) value we got are 5.05, 7.85 and 3.82, respectively. Then the three models are combined into a comprehensive evaluation model by model combination method. The RMSE of the test results is 3.30. The results show that the combined model is superior to one individual model and it is a more accurate and stable method
The spring Yellow Sea fog: synoptic and air-sea characteristics associated with different airflow paths
No full textThe fog occurs frequently over the Yellow Sea in spring (April-May), a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provided associated with the fog for the period of 1960-2006. The sea fog is categorized by airflow pathways of backward trajectory cluster analysis with the surface observations derived from international comprehensive oceanatmosphere dataset (I_COADS) I_COADS datasets and contemporaneous wind fields from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis. On the basis of the airflow paths, the large-scale lower-tropospheric circulation patterns and the associated surface divergence, the distribution of a vertical humidity, the horizontal water vapor transportation and the air-sea temperature difference are investigated and the major findings are summarized as follows. (1) Four primary clusters of the airflow paths that lead to spring sea fog formation are identified. They are originated from the northwest, east, southeast and southwest of the Yellow Sea, respectively. (2) Springtime Yellow Sea fog occurs under two typical weather patterns: the Yellow Sea high (YSH) and cyclone and anticyclone couplet (CAC). Each pattern appears by about equal chance in April but the YSH occurrence drops to around one third and the CAC rises to around two third of chance in May. (3) The common feature in the two types of synoptic conditions is that surface divergence center is located over the Yellow Sea. (4) For the YSH type of fog, water vapor comes mainly from local evaporation with a well-defined dry layer present in the lower atmosphere; for the CAC type of fog, however, water vapor comes mainly from areas outside the Yellow Sea with a thick surface layer of high humidity. (5) With the differences in weather patterns and its associated vertical distribution of the humidity and the transportation of water vapor, there are two types of sea fogs. Most fogs of the CAC types are "warm" fog, while fogs of YSH type have nearly equal chance to be "warm" and "cold" fog
Observational evidence for turbulent effects on total suspended matter within the Pearl River plume
No full textWe observed the structure of the Pearl River plume and its turbulent characteristics, and investigated the turbulent effect on total suspended matter (TSM) within its "far-field" region, based on in situ and satellite data collected in June 2015. A significant northeastward plume was created under southern monsoonal conditions. The in situ data provided the width, depth, and velocity of the plume, as inferred by salinity. Weaker turbulence occurred at the front surface position than in the plume zone. Stronger turbulence induced greater turbidity in the bottom boundary layer; however, the surface mixed layer differed. By estimating the turbidity budget, we found the lateral fluxes term was the largest term in the plume, turbulent fluxes comprised the second largest term, and the settling terms comprised the smallest term. We quantified the turbulent mechanisms and found that stronger river discharge induced greater TSM turbidity. Tidal and buoyancy fluxes had minor regulatory effects on TSM. Our observations suggest that TSM in the "far field" region originated from the Pearl River and the coastal region
Natural gas migration and accumulation model and favorable exploration targets in Ordovician dolomite in Jingxi, Ordos Basin
No full textThe Ordovician dolomite reservoir in Ma5(5)-Ma5(10) sub-members in Jingxi in Ordos Basin is a newly discovered field with multiple natural gas pools. The gas accumulation patterns of the reservoir are unclear. Considering the geological background, the genesis, migration, and accumulation of natural gas in Jingxi were studied systematically, and favorable exploration targets were predicted. Natural gas in Ma5(5)-Ma5(10) sub-members is a mixture of Upper Paleozoic and Ordovician products. The Upper Paleozoic coaliferous gas was mainly expulsed downward through the hydrocarbon-providing window where the coal-bearing source rocks made contact with the dolomite reservoirs. The gas then migrated from west to east and accumulated under the condition of lithology variation. The Ordovician petroliferous gas mainly migrated from bottom to top through fractures and mixed with the coaliferous gas in Ma5(5)-Ma5(10) sub-members. The natural gas reservoir formation model was summarized as the migration of gas over a short distance and partial charging into the dolomite reservoirs from the Late Triassic to Middle Jurassic, and the migration of gas over a long distance and massive charging into the dolomite reservoirs during the Late Cretaceous. Ma5(5) and Ma5(6) sub-members are the focus of further exploration, and petroliferous gas in Ma5(7)-Ma5(10) sub-members deserves attention. The dolomite reservoirs of the hydrocarbon-providing windows and the east of these locations are the favorable exploration targets
Sediment provenance in the western Pacific warm pool from the last glacial maximum to the early Holocene: Implications for ocean circulation and climatic change
No full textSedimentary records including clay minerals, major elements, rare earth elements (REE) and C-14 ages, were analyzed in one core from the western Pacific warm pool (WPWP), in order to identify the sources of sediments in the warm pool region from the last glacial maximum (LGM) to the early Holocene. The results showed that the sedimentation rate at the studied core site has decreased continuously since the LGM. Both major elements and clay minerals experienced staged changes in the study area. In the studied core, most major elemental concentrations decreased prior to 22 kyr BP but increased gradually after 13 kyr BP. Sediment provenance based on clay minerals and REEs further revealed that sediments were likely a mixture of dominant New Guinea sediments and Asian dust. The South Equatorial Current was the main force transporting New Guinea particles, while the East Asian winter monsoon and the correlated North Equatorial Countercurrent might have loaded the Asian dust into the study area. Moreover, Heinrich events were well imprinted in the western Pacific, and another cold climatic event that occurred at approximately 21 kyr BP was also recorded in the study area. These events were similarly documented in ice from Greenland but were undistinguished in ice from the Antarctic and stalagmites from the Hulu Cave, China. A frequency analysis of multi-proxies confirmed that sun irradiance essentially controlled the variation in sedimentary records in the western Pacific from the LGM to the early Holocene
西北太平洋及其边缘海的放射虫群与环境变化
No full text西北太平洋从低纬度的赤道至高纬度的白令海,跨越近66°N的大范围海域,包括开阔大洋及其相互连接的白令海、鄂霍次克海、日本海、东海、南海、菲律宾海等边缘海,具有不同类型的地理气候与海洋环境,构成较完整的大洋-边缘海环境体系。系统开展西北太平洋浮游性放射虫的区域分布特征分析,将有助于深入了解放射虫化石群指示的生物地理、水团特性、海流搬迁与气候变化的环境信息,
微体古生物学研究的若干关键技术标准探讨
No full text2017年10月14日,国家标准《海洋沉积物间隙生物调查规范》BG/T34656—2017(以下简称《标准》)由国家标准化技术委员会正式发布实施,这是我国自本世纪80年代以来首次新制定并实施有关海洋微体古生物调查的国家标准。《标准》由中国科学院海洋研究所主持,同济大学、国家海洋局第一海洋研究所、国家海洋局第二海洋研究所、国家海洋局第三海洋研究所、中国地质调查局青岛海洋地质研究所、中国科学院南海海洋研究所、中国地质大学(北京)、中国科学院南京地质古生物研究所、中国海洋大学共十家涉海单位的多位知名专家和学者共同参与起草
南沙群岛海域油气资源共同开发法律问题研究
No full text南海问题错综复杂,南沙群岛海域油气资源的开发成为争端各国关注的焦点。解决争议海域油气资源开发问题的最佳途径就是共同开发。本文通过论述共同开发的相关理论,提出背景和法律依据,结合争议海域油气资源共同开发的国际实践,分析我国南沙群岛海域油气资源的现状及各国的相关政策,总结出南沙群岛海域油气资源共同开发存在可能性,同时也困难重重。面对种种困难,我国应该积极采取应对措施,进一步加强对南海断续线及线内水域性质和地位的研究,加大开发力度并处理好先存权问题,构建南沙群岛海域油气资源共同开发的合理模式
海南岛东北部海域海砂资源特征及成因
No full text海南岛周边浅海海砂资源丰富,其东北部海域砂、砾质沉积物分布面积可达数百平方千米,平均厚度超过10m,均为全新世海相沉积。通过对海南岛东北部海域的水深、地层、沉积物粒度等方面的调查,研究了该区域海砂资源的分布、范围、规模、厚度及沉积环境,对海砂的质量和开发利用进行了初步分析。其中,位于琼州海峡东口的潮流沙脊区是海砂的主要分布区域,沉积厚度在20m以上,海砂分选好、次圆状,砂含量超过80%,海砂各项指标良好,用途广泛。研究区海砂资源主要受海底地形和潮流的共同作用而形成,属全新世陆架潮流沉积体系,近岸处亦受到陆域物质输入和浅水波浪的影响,沉积物来源主要为琼州海峡内部和粤西,海南岛的物质供给可能相对较少