青草沙水库工程对附近水域河床冲淤的影响

青草沙水库是长江河口的一个重大工程,显著改变了北港上段的河势。河势的变化会引起流场和泥沙质量浓度的变化,进而影响河床的冲淤。本文应用三维水动力和泥沙数值模式,计算和分析了青草沙水库工程对附近水域流场、泥沙质量浓度和冲淤的影响。青草沙水库工程建设后,北港河道束窄,导致水库北侧河道主槽流速和泥沙质量浓度增加。水库工程使得进入北港的径流量和纳潮量减少,导致青草沙水库以东、北港下段和拦门沙区域流速和泥沙质量浓度下降。应用半理论半经验河床冲淤公式和模式计算的工程前后流速、泥沙质量浓度和水位数据,给出了由水库工程造成的河床冲淤变化分布。在水库以北北港水域发生普遍冲刷,冲刷强度最大可达2~3 m,冲淤分布和量值与工程前后实测水深变化吻合良好。数值模式较好地模拟了青草沙水库工程对附近水域冲淤分布的影响和变化量值。     

Low-frequency coupled atmosphere-ocean variability in the southern Indian Ocean

The low-frequency atmosphere-ocean coupled variability of the southern Indian Ocean(SIO) was investigated using observation data over 1958-2010.These data were obtained from ECMWF for sea level pressure(SLP) and wind,from NCEP/NCAR for heat fluxes,and from the Hadley Center for SST.To obtain the coupled air-sea variability,we performed SVD analyses on SST and SLP.The primary coupled mode represents 43% of the total square covariance and is featured by weak westerly winds along 45-30 S.This weakened subtropical anticyclone forces fluctuations in a well-known subtropical dipole structure in the SST via wind-induced processes.The SST changes in response to atmosphere forcing and is predictable with a lead-time of 1-2 months.Atmosphere-ocean coupling of this mode is strongest during the austral summer.Its principle component is characterized by mixed interannual and interdecadal fluctuations.There is a strong relationship between the first mode and Antarctic Oscillation(AAO).The AAO can influence the coupled processes in the SIO by modulating the subtropical high.The second mode,accounting for 30% of the total square covariance,represents a 25-year period interdecadal oscillation in the strength of the subtropical anticyclone that is accompanied by fluctuations of a monopole structure in the SST along the 35-25 S band.It is caused by subsidence of the atmosphere.The present study also shows that physical processes of both local thermodynamic and ocean circulation in the SIO have a crucial role in the formation of the atmosphere-ocean covariability.     

THE CLIMATIC JUMP OF THE WESTERN PACIFIC WARM POOL AND ITS CLIMATIC EFFECTS

1INTRODUCTIONTropicalwesternPacificOceanisanareathathasthehighestoceantemperatureacrosstheglobe.Asmostofthewarmwaterconcentratesintheregion,itisknownasthe搘esternPacificwarmpool?Asshowninsomestudies[1-5],thegeneralcirculationandshort-termclimaticchangeswillbeseriouslyaffectedifthermodynamicconditionchangesinthewaters,whichthenhaveanimportantroletoplayintheonsetofanyENSOepisodes.Therehasnotbeenanyunifieddefinitionoftheindexforthewarmpool.FollowingthecriterionofWyrtki[4],however,theareae…     

黄海南部及东海北部夏季若干水文特征

本文就近几年作者在黄海南部和东海北部进行调查研究(夏季)的主要成果予以阐述,结论为:(1)南黄海底层冷水可进一步划分为三个次级水团;(2)潮混合对黄海冷水团边界和黄海温跃层等有重要影响,它还形成海面的陆架锋;(3)夏季南黄海上层存在着闭合的密度环流,而黄海沿岸流性质上属锋面强流,济州岛西南存在着气旋式海水运动;(4)黄海暖流不再深入黄海冷水团内部,但其内部可能存在着方向相反的一对弱环流;(5)长江口海区存在着可能是因台湾暖流逆坡行进产生的上升流现象。     

杭州湾、长江口余流及其物质输运作用的模拟研究Ⅰ.杭州湾、长江口三维联合模型

根据杭州湾、长江口流场和物质输运的特点,引进正交曲线网格版本ＥＣＯＭ模型,并对斜压梯度力和物质对流扩散的计算作了改进,建立了一个以杭州湾和长江口为整体的三维联合模型,用于潮流、余流和物质输运的计算和研究．     

黄海冷水团对长江冲淡水扩展的影响

利用作者已建立的σ坐标系下三维非线斜压陆架模式,研究黄海冷水团对长江冲淡水扩展的影响。数据试验结果表明,黄海冷水团产生的余流,与黄海冷水团的强度和海底地形有关。     

杭州湾、长江口余流及其物质输运作用的模拟研究Ⅱ冬季余流及其对物质的运输作用

首先分析了杭州湾、长江口冬季余流和物质输运作用的观测特征,提出了几个值得继续研究的问题．然后,利用杭州湾、长江口三维联合模型,综合考虑径流、风应力、密度流、中国东部海域背景环流和Ｍ２,Ｓ２,Ｋ１,Ｏ１四个分潮的综合作用,模拟出了冬季的余流结构及其对物质的输运作用．在此基础上,针对所总结的几个问题,进一步作数值模拟,讨论余流和物质输运作用形成的机制。     

Ventilation of the North Pacific Ocean: Water exchange between subtropical and tropical gyres

INTRODUCTIONIntheearly 1 980 s,ventilationtheoryemergedtopredictthehorizontalandverticalstructureofthethermocline.Thereweretwodifferentviewsonthestratifiedoceans.Thefirsttheory (RhinesandYoung,1 982 ,hereafterRY ;YoungandRhines,1 982 )proposedanunventilatedmodelinwhichonlytheuppermostlayerisexposedtothesurfaceandisforcedbythewindstress.Thesecondtheory (Luytenetal.,1 983 ,hereafterLPS)offeredaventilatedmodelwhichisclosertotheclassicalthermoclinetheoriesthanthatofthefirstone (e.g .,Nee…     

Water transports through the four main straits around the South China Sea

A quasi-global high-resolution HYbrid Coordinate Ocean Model (HYCOM) is used to investigate seasonal variations of water transports through the four main straits in the South China Sea. The results show that the annual transports through the four straits Luzon Strait, Taiwan Strait, Sunda Shelf and Mindoro Strait are −4.5, 2.3, 0.5 and 1.7 Sv (1 Sv=10⁶ m³s⁻¹), respectively. The Mindoro Strait has an important outflow that accounts for over one third of the total inflow through the Luzon Strait. Furthermore, it indicates that there are strong seasonal variations of water transport in the four straits. The water transport through the Luzon Strait (Taiwan Strait, Sunda Shelf, Mindoro Strait) has a maximum value of −7.6 Sv in December (3.1 Sv in July, 2.1S v in January, 4.5Sv in November), a minimum value of −2.1 Sv in June (1.5 Sv in October, −1.0 Sv in June, −0.2 Sv in May), respectively. Supported by National Natural Science Foundation of China (No. 40806012, 40876013), Open Fund of the Key Laboratory of Ocean Circulation and Waves, Chinese Academy of Sciences (No. KLOCAW0803) and Scientific Research Foundation for talent, Guangdong Ocean University (No. E06118)     

河口大型围垦工程中龙口水动力特点

河口大型围垦工程围区吞吐潮量大,河口滩势条件复杂,龙口位置选择和极值流速确定是工程设计中的关键环节。以两个典型河口大型围垦工程龙口为例,从水动力分析角度提出合理的龙口平面选址和龙口渡汛时因地制宜的结构布置。在青草沙水库工程中,龙口位置的确定充分利用围区原有深槽的过流能力,以保证库区内外及时水交换,并兼顾到围堤实施顺序与工程区整体河势环境相协调,避免口门进出水引起工程河段滩地的大冲大淤,也确保了堤基安全。龙口渡汛需要面临长时间大潮汛过流考验,龙口流速大小决定了龙口结构的保护方案和后期的合龙方案,常规使用的堰流计算方法能较为准确地计算龙口流量和断面平均流速过程,数值模型能对大型龙口流速空间分布情况进行很好的模拟,是常规计算方法的重要补充。计算结果表明口门横向上中心流速大于口门两侧流速,在纵向上底坡内外两侧顶角处水流受重力作用加强,垂向断面收缩,在涨、落急时刻分别形成大流速区,是龙口结构布置时重点抗冲保护区域,需要设置抗冲性较强、自重大且联接牢固的护面材料。此外,同一潮周期内涨急流速通常大于落急流速也是其重要水动力特点。