Observed residual currents off the Changjiang （Yangtze） Rivermouth in summertime of 1959 and 1982     

朱建荣戚定满  肖成猷 《中国海洋湖沼学报》2004,22(3):250-255

Data taken in two large scale ocean observations in China in summer 1959 and 1982 were used to analyze the residual current off the Changjiang (Yangtze) River mouth. The currents at surface off the mouth in July 1959 and 1982 flow northeastward and eastward due to the river discharge, the current speed was larger in 1982 than in 1959. All the bottom currents flow landward due to baroclinic effect. The surface current was controlled by the river runoff and the Taiwan Warm Current (TWC). A return current at surface off the mouth was observed in September 1959. In general, the bottom currents were controlled by the TWC in most study area in addition to the runoff near the mouth. Although driven by 3-D model with the monthly averaged forces (river discharge, wind stress, baroclinic effect, open boundary water volume flux and tidal mixing) in August, the simulated circulations were basically consistent with the observed ones with episodic time manner.  相似文献   

THE STATISTICAL DISTRIBUTION OF THE SPATIAL MAXIMA OF A WAVY SEA SURFACE   总被引：2，自引：0，他引：2  

孙孚  丁平兴  管长龙 《中国海洋湖沼学报》1994,12(1):1-12

A statistical distribution of the maxima of a random function in two space variables is suggested to fit with stereo observations of the sea surface. The presented distribution is a complicated mix of Gaussian, Rayleighian and Maxwellian distributions and determined by three parameters of the directional spectrum, According to the changes of the three parameters it may approach the above three distributions respectively in special cases so that it has more probability of fitting stereo data better In addition, the fact that these parameters can be directly estimated from observed data is briefly in the paper.  相似文献   

崇明岛的变迁   总被引：4，自引：0，他引：4  

褚绍唐 《地理研究》1987,6(3):9-16

本文讨论了崇明岛何时设镇、崇明县址的迁移及崇明岛的变迁等三个问题,澄清了历代县志记载混乱而产生的一些问题。  相似文献   

ON THE VERTICAL STRUCTURE OF TIDAL CURRENTS IN SHALLOWWATER NEAR THE CHANGJIANG RIVER ESTUARY     

李身铎 《中国海洋湖沼学报》1987,5(1):22-33

This research on the vertical structure of tidal current in shallow water near the Changjiang River estuary is based on a great deal of observation data of current obtained recently, and a simple mathematic model. The essential features of the structure are: (1) the maximum velocity decreases with depth, the shallower the water, the lower the velocity; (2) the orientation of maximum velocity continuously deviates from the surface to the bottom to the left at the western side of the mouth bar and to the right at the eastern side; (3) the time of maximum velocity leads steadily with depth; (4) in general, tidal currents rotate clockwise, the nearer the sea-bed, the narrower the ellipse of the tidal current; (5) the ratio W1/W2 varies non-linearly with depth, and is smaller in the middle layer than at the surface and bottom. Bottom friction is the main cause of the vertical structure.  相似文献   

配饵中不同大豆浓缩蛋白含量对中华绒螯蟹消化酶活力的影响   总被引：3，自引：0，他引：3  

李二超陈立侨  蔡永久顾顺樟  洪美玲张璐 刘超 《广东海洋大学学报》2006,26(4):14-21

研究了大豆浓缩蛋白作为饵料蛋白源对中华绒螯蟹幼蟹消化酶活力的影响．初步探讨了中华绒螯蟹对饵料蛋白源的内在适应机理。根据中华绒螫蟹的营养需求．用大豆浓缩蛋白替代鱼粉作为蛋白源配制成6种近似等蛋白等能的饵料，其中大豆浓缩蛋白在饵料中的含量分别为0、11％、22％、33％、44％和56％（分别替代鱼蛋白质量的0、18．64％、37．93％、56．90％、77．19％和100%），对照饵料全部以鱼粉作为蛋白源。用上述6种饵料喂养中华绒螫蟹50d后．测定蟹肝胰腺各种消化酶活力。结果表明：随着饵料中大豆浓缩蛋白含量的升高，胃蛋白酶和胰蛋白酶活力均芏降低之势。当大豆浓缩蛋白含量达到44％时，与全鱼粉对照组相比．胃蛋白酶和胰蛋白酶活力显著性降低（P〈0．05）；同时，淀粉酶稍呈升高之势，而纤维素酶则稍呈降低的趋势；A／T、比例呈显著上升的趋势。半大豆浓缩蛋白含量达44％时，与对照组有显著性差异，说明河蟹对植物蛋白有很强的适应性。  相似文献   

Human impact on the historical change of CO<Subscript>2</Subscript>degassing flux in River Changjiang   总被引：2，自引：0，他引：2  

FuShun Wang  Yuchun Wang  Jing Zhang  Hai Xu  Xiuguo Wei 《Geochemical transactions》2007,8(1):7

The impact of water quality changes in River Changjiang (formally known as the Yangtze River) on dissolved CO₂ and silicate concentrations and seasonal carbon flux in the past several decades (1960s–2000) was evaluated, based on monitoring data from hydrographic gauge. It was found that dissolved CO₂ and silicate in Changjiang decreased dramatically during this decades, as opposed to a marked increase in nutrient (e.g. NO₃ ^-) concentrations. Our analyses revealed that dissolved CO₂ in Changjiang was over-saturated with the atmosphere CO₂, and its concentration had showed a declining trend since the 1960s, despite that fluvial DIC flux had maintained stable. Analysis results also suggested that the decrease in dissolved CO₂ concentration was attributed to changes on the riverine trophic level and river damming activities in the Changjiang drainage basin. Due to the economic innovation (e.g. agriculture and industry development) across the Changjiang watershed, fertilizers application and river regulations have significantly altered the original state of the river. Its ecosystem and hydrological condition have been evolving toward the "lacustrine/reservoir" autotrophic type prevailing with plankton. Accordingly, average CO₂ diffusing flux to the atmosphere from the river had been reduced by three-fourth from the 1960s to 1990s, with the flux value being down to 14.2 mol.m^-2.yr^-1 in the 1990s. For a rough estimate, approximately 15.3 Mt of carbon was degassed annually into the atmosphere from the entire Changjiang drainage basin in the 1990s.  相似文献   

A new Doppler frequency anomaly algorithm for surface current measurement with SAR     

Wang  Lihua  Gao  Yanghua  Lu  Peng  Fan  Li  Zhou  Yunxuan 《中国海洋湖沼学报》2022,40(2):470-484

Journal of Oceanology and Limnology - Values for Doppler center frequency are calculated from the echo signal at the satellite using the Doppler centroid method and so include the predicted Doppler...  相似文献   

Comparison of the graphic and moment methods for analyzing grain-size distributions: A case study for the Chinese inner continental shelf seas     

《国际泥沙研究》2022,37(6):729-736

  相似文献   

The complexity of luminescence dating of tidal sand body revealed by the discrepancy of paired quartz OSL ages     

《Quaternary Geochronology》2022

Optically stimulated luminescence (OSL) dating is becoming a useful technique to yield absolute age of organic-poor sandy deposits. The buried tidal sand body (BTSB) in the coastal zone of northern Jiangsu Province, China, has been suggested to have the same origin as the offshore radial sand ridge in the Yellow Sea. However, chronological constrain of the BSTB is still quite limited. In this study, OSL measurements were conducted using silt-sized multi-grain and coarse-grained single-grain quartz to constrain the depositional history of a 25.6 m core from the BTSB. A low luminescence sensitivity of quartz was observed, and only ∼1.04% of the grains passed the standard rejection criterion for single-grain measurement. Analysis of paired OSL ages from two grain-size fractions using different protocols showed that silt-sized quartz ages were underestimated of 0.14–1.35 ka in comparison to coarse-grained quartz in the depth interval of 5.8–22.4 m. We interpret such an age discrepancy as the effects of lateral infiltration of fine-grained sediment into the sand body due to dynamic feature of channel-ridge system on the shelf. As far as we know, it is the first time that such infiltration is demonstrated through OSL dating. Our OSL data indicated that there is a significant hiatus between the Late Pleistocene stiff clay layer (50–18 ka) and the Holocene sequence. Holocene deposits only occurred in the last 2 ka, with rapid accumulation of ∼17 m-thick sediments at ∼2–1 ka, a slower accumulation between ∼1 and 0.1 ka and rapid land emergence through an accretion of ∼4 m-thick sediment over the past ∼0.1 ka. This study highlights the complexity of OSL dating in highly dynamic sedimentary environments. Therefore, examining different grain size fractions and comparing different measurement protocols are highly deserved in carrying out OSL dating in such environments.  相似文献   

Reconstruction of the Changjiang River tidal-limit movement since the ninth century AD          下载免费PDF全文

Zhang Ren-Shun  Gao Chao  Wang Ya-Ping 《古地理学报》2021,22(6):1221-1232

The tide can now propagate upstream for more than 600 km from the Changjiang River estuary to hinterland,which is rare in the world. In China,information and records reflecting tidal limit and its movement in the Changjiang River can be found from some ancient books,literary works and local chronicles. At the end of the 3rd and the beginning of the 4th century AD, the tide limit of the Changjiang River reached the upstream of Chaisang(now named Jiujiang in Jiangxi Province). At the early 9th century,the tide limit in the dry season retreated to the Penpukou in Jiujiang. In the last ten years of the 13th century,the tidal limit moved back to the Xiaogushan Mountain near the border between Anhui Province and Jiangxi Province. By the middle of the 20th century,the modern researchers generally agreed that the tidal limit retreated to Datong in Anhui Province. Before the main stream of the Changjiang River was cut off by large-scale water conservancy projects,the tide limit had retreated seaward continuously. From the 3rd decade of the 9th century to the last decade of the 13th century,the tide limit moved downstream 64 km during the 470 years,with an average annual rate of 0.136km/a. During the 670 years from the end of the 13th century to the middle of the 20th century,the tide limit had moved downstream 170 km,with an average annual rate of 0.254 km/a,almost twice as much as that of the previous period. We suggest the climate change accounted for the different retreat rate of the tidal limit between the two periods discussed. In addition,a recent study found that during the extremely dry periods,when the discharge of Jiujiang station was about 8440 m³/s,the tidal limit reached near Jiujiang. In the years when the water conservancy project on the main stream of the Changjiang River began to store water,the tide limit actually returned to the previous position of the middle Tang Dynasty,i.e. 1100 years ago.  相似文献