Nearshore sticky waters     

《Ocean Modelling》2014

Wind- and current-driven flotsam, oil spills, pollutants, and nutrients, approaching the nearshore will frequently appear to slow down/park just beyond the break zone, where waves break. Moreover, the portion of these tracers that beach will do so only after a long time. Explaining why these tracers park and at what rate they reach the shore has important implications on a variety of different nearshore environmental issues, including the determination of what subscale processes are essential in computer models for the simulation of pollutant transport in the nearshore. Using a simple model we provide an explanation for the underlying mechanism responsible for the parking of tracers, not subject to inertial effects, the role played by the bottom topography, and the non-uniform dispersion which leads, in some circumstances, to the eventual landing of all or a portion of the tracers. We refer to the parking phenomenon in this environment as nearshore sticky waters.  相似文献   

基于实时几何流线生成的二维海流数据交互可视化方法   总被引：1，自引：0，他引：1  

何珏  田丰林  张昉  陈戈 《海洋技术学报》2015,34(3):91-96

海流可视化是海洋科学研究的热门领域。目前已有的可视化方法在视觉清晰度、真实度和运行效率等方面存在不足之处。文中提出一种新的基于实时几何流线生成的二维海流数据交互可视化方法。该方法实现了全球海流的时空连续表达,可较好地展现全球海流特征;采用概率的方法控制粒子密度,使全球范围内粒子保持均匀分布的状态;生成的流线清晰且具有较高的可调整性。通过MSLA和SODA两个示例数据集的可视化和性能分析证实了此方案具有很高的实用性和灵活性,可视化结果可以较好地反映全球洋流特征。  相似文献   

Assessing SARAL/AltiKa Data in the Coastal Zone: Comparisons with HF Radar Observations     

Ananda Pascual  Arancha Lana  Charles Troupin  Simón Ruiz  Yannice Faugère  Romain Escudier 《Marine Geodesy》2015,38(3):260-276

We present an initial assessment of SARAL/AltiKa data in the coastal band. The study focuses on the Ibiza Channel where the north-south water exchanges play a key role in controlling the circulation variability in the western Mediterranean. In this area, the track 16 of SARAL/AltiKa intercepts the domain covered by a coastal high-frequency (HF) radar system, which provides surface currents with a range up to 60 km. We evaluate the performance of the SARAL/AltiKa Ssalto/Duacs delayed-time along-track products compared to the HF radar surface velocity fields. SARAL/AltiKa data are retrieved at a distance of only 7 km from the coast, putting in evidence the emerging capabilities of the new altimeter. The derived velocities resolved the general features of the seasonal mesoscale variability with reasonable agreement with HF radar fields (significant correlations of 0.54). However, some discrepancies appear, which might be caused by instrumental hardware radar errors, ageostrophic velocities as well as inaccurate corrections and editing in the altimeter data. Root mean square (rms) differences between the estimated SARAL/AltiKa and the HF radar velocities are about 13 cm/s. These results are consistent with recent studies in other parts of the ocean applying similar approaches to Topex/Poseidon and Jason-1 missions and using coastal altimeter corrections.  相似文献   

星载SAR测量海洋流场研究进展     

何宜军  杨小波  矣娜  刘保昌 《南京气象学院学报》2020,12(2):181-190

多普勒信息是合成孔径雷达（SAR）进行海洋动力遥感的一个重要参数,自从20世纪80年代末就已经开始利用该参数反演海表面动力过程的相关研究.本文重点论述了星载SAR多普勒信息反演海表面流及其应用研究,主要包括SAR干涉测量方法获取海洋流场信息的主要技术手段及研究进展;多普勒频移方法反演表层海洋流场的发展历程及在上层海洋现象（包括地转流、准地转流以及中小尺度过程）中的应用研究;相关的国外重要数据融合计划和研发计划.目前国内在海洋流场的遥感方面还处于起步阶段,重点关注于反演理论和方法,而将反演信息应用于上层海洋动力的研究,还十分缺乏.希望通过本文的综述,为后续在该方向的研究提供借鉴.  相似文献   

Spatial Distribution of Contourites in Global Ocean and Its Paleoclimatic Significance—The Contribution of International Ocean Drilling to the Studies of Contourites     

Yulong Zhao  Zhifei Liu 《地球科学进展》2017,32(12):1287-1296

Contourite is one of the most important type of sediments in the global ocean, which has recorded significant information on paleoclimatic changes. It is also of great importance for ocean engineering and marine hydrocarbon exploration. The development of scientific ocean drilling, especially the “Integrated Ocean Drilling Program” and the undergoing “International Ocean Discovery Program”, has made great contribution in mapping the spatial distribution of contourites and revealing contourite-related paleoclimatic information, through coring and geophysical exploration in the global ocean. It is found that the global distribution of contourites is controlled predominantly by the global deep-water circulation while its distribution in a specific region can be affected by the intensity of deep currents, tectonic activities, sediment supply, and so on. The geological changes in the global deep-water circulation is, however, further affected by tectonic activities, origins of water masses, as well as climate changes, e.g. the Cenozoic global cooling, changes in the size of the northern hemisphere ice caps, and intensity of monsoon. The main controlling factors of deep water circulation vary with different regions.  相似文献   

Sediment resuspension and transport in Lake Michigan during the unstratified period   总被引：2，自引：0，他引：2  

Nathan Hawley  & Chang-Hee Lee 《Sedimentology》1999,46(5):791-805

Instrumented moorings were deployed during the winter of 1994–95 at three depths (28, 58 and 101 m) in southern Lake Michigan. Storms during the observation period were not unusually severe, so the processes observed are typical of those that occur during an average winter. Time series observations of water temperature, beam attenuation coefficient (a measure of water transparency) and current velocity show that local resuspension of bottom sediment occurred frequently after the breakdown of the thermocline. Resuspension was most frequent close to the shore but was also observed at the 58 m station. Local resuspension did not occur at the 101 m station, but advection to the site of material resuspended at shallower sites was observed. These observations do not support the hypothesis proposed by previous investigators that local resuspension at depths of 100 m or greater occurs during the unstratified period. It is more likely that fine-grained material resuspended by storm action in intermediate water depths (≈ 30–60 m) is transported into the deeper parts of the lake by the general lake circulation.  相似文献   

Characteristics of near-surface electrokinetic coupling   总被引：2，自引：0，他引：2  

David Beamish 《Geophysical Journal International》1999,137(1):231-242

Naturally occurring electric potentials at the Earth's surface are traditionally studied using self-potential geophysics. Recent theoretical and experimental work has reinvestigated the manner in which the measurement can be made dynamically using a pressure source. The methodology, often referred to as seismoelectric, relies on electrokinetic coupling at interfaces in the streaming potential coefficient. The ultimate aim of the developing methodologies lies in the detection of zones of high fluid mobility (permeability) and fluid geochemical contrasts within the subsurface. As yet there are no standard methods of recording and interpretation: the technique remains experimental. Field measurements are made using a seismic source and by recording electric voltage across arrays of surface dipoles. This study presents observational characteristics of electrokinetic coupling based on experiments carried out in a wide range of environments. Theory concerning the coupled elastic and electromagnetic wave equations in a saturated porous medium is discussed. It is predicted that coupling will produce electromagnetic radiation patterns from vertical electric dipoles generated at interfaces. Surface- and body-wave coupling mechanisms should provide different time–distance patterns. Vertical electric dipole radiation sources are modelled and their spatial characteristics presented. A variety of experimental configurations have been used, and geometries that exploit phase asymmetry to enhance the separation of signal and noise are emphasized. The main experimental results presented are detailed observations in the immediate vicinity of the source. Simultaneous arrivals across arrays of surface dipoles are not common. The majority of such experiments have indicated that shot-symmetric voltages which display low-velocity moveout are the dominant received waveforms.  相似文献   

古长江河口湾充填潮流作用机制的初步探讨   总被引：10，自引：0，他引：10  

朱玉荣 《海洋学报》1999,21(3):73-82

长江三角洲的发育是以古长江河日湾的充填来实现的.研究潮汐、潮流在古长江河口湾充填中所起的作用,可深入了解长江三角洲的形成发育过程.建立了渤海、黄海、东海的二维潮流数学模型,数值模拟了冰后期最大海侵,即现今长江三角洲地区为巨大河口湾时的M2潮汐、潮流.在此基础上,计算了古长江河口湾及其周围海域8种粒径泥沙的潮平均悬移与推移输沙率,并根据输沙率散度的正负,划分了海底冲刷区与淤积区.根据计算结果得出,冰后期最大海侵时,存在大致以古长江河口湾湾口中点为腹点、波腹线向海凸起的独特驻潮波波腹区.在其控制下,外海潮流大致以古长江河口湾湾口中点为顶点作辐聚、辐散运动.在古潮流场作用下,经历每一个潮周期后,古长江河口湾周围海域的泥沙均向河口湾内净输运,并在河口湾内淤积.古长江河口湾的充填是在长江带来大量泥沙,外海的潮汐、潮流又有利于泥沙向河口湾内净输运,且在河口湾内沉积的情况下实现的.外海的潮汐、潮流为古长江河口湾的充填、长江三角洲的发育提供了必要而又有利的水动力环境.  相似文献   

潮流准调和分析的软件实现   总被引：1，自引：0，他引：1  

唐岩  罗世华  宋刚福  暴景阳  许军 《海洋测绘》2006,26(2):34-36

较之潮汐分析、预报的研究而言,目前关于潮流的计算还相对落后。简要论述潮流准调和分析与预报的基本原理,编程实现了潮流准调和分析、准调和预报以及潮流椭圆绘制,并具体给出了实际算例,用以说明该程序的可用性和正确性。  相似文献   

中国东部海域潮汐余流特征及其动力分析     

陈元杰  程鹏 《海洋通报》2021,40(4)

潮汐余流对中国东部海域物质输运过程起着重要作用。通过对中国东部海域的三维数值模拟,计算了潮汐余流并从潮余涡量角度分析了其形成机制。中国东部海域的欧拉余流在水深较浅的朝鲜半岛沿岸、苏北浅滩、长江浅滩、闽浙沿岸,以及冲绳海槽附近海域,流速量级较大,以余流涡旋的形式呈现,其机制为局部地形差异和潮汐水位高度波动下,科氏效应或摩擦效应导致潮周期内存在净涡量。斯托克斯漂流量级在浅水区较大,而在深水海域则远小于欧拉余流。拉格朗日余流在深水区域与欧拉余流相似,在浅水区域由欧拉余流和斯托克斯漂流共同决定。输运余流和拉格朗日余流分布特征更接近,特别是在近岸海域,但两者的物理意义并不相同。潮汐余流由于常年稳定存在,且在许多海域的流动方向同已知的沿岸流系的方向基本一致,是中国东部海域沿岸流的重要组成部分。估算出了输运余流对沿岸流的贡献率或抑制率,输运余流对近岸陆源沉积物输运和沉积物分布具有不可忽略的作用。  相似文献