共查询到20条相似文献，搜索用时 250 毫秒
1.
程鹏 《海洋学报(英文版)》2020,42(5):1-2
在受波动影响的近岸浅水区域，运用sigma坐标是计算平均水位附近的余流的有效途径。本项研究在理论上分析了在狭窄潮汐水道中sigma坐标下的余流的物理意义，并运用一系列的理想化数值模型对分析结果进行了验证。对于浅水波，sigma层和水体中的波动面相一致，因而斯托克斯速度及其分量可以用sigma坐标上的速度来表达。一个sigma层上的余流（即sigma余流）是位于这一sigma层平均深度上的欧拉余流和斯托克斯速度垂向分量的和，可以被看做是半拉格朗日余流。因为斯托克斯速度的垂向分量比其水平分量小一个量级，sigma余流可看做为欧拉余流的近似。在sigma层上的物质输运余流是sigma余流和斯托克斯速度水平分量的和，在大小和方向上和拉格朗日余流近似。 相似文献
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Gas in sediments has become an important subject of research for various reasons. It affects large areas of the sea floor
where it is mainly produced. Gas and gas migration have a strong impact on the environmental situation as well as on sea floor
stability. Furthermore, large research programs on gas hydrates have been initiated during the last 10 years in order to investigate
their potential for future energy production and their climatic impact. These activities require the improvement of geophysical
methods for reservoir investigations especially with respect to their physical properties and internal structures. Basic relationships
between the physical properties and seismic parameters can be investigated in shallow marine areas as they are more easily
accessible than hydrocarbon reservoirs. High-resolution seismic profiles from the Arkona Basin (SW Baltic Sea) show distinct
‘acoustic turbidity’ zones which indicate the presence of free gas in the near surface sediments. Total gas concentrations
were determined from cores taken in the study area with mean concentrations of 46.5 ml/l wet sediment in non-acoustic turbidity
zones and up to 106.1 ml/l in the basin centre with acoustic turbidity. The expression of gas bubbles on reflection seismic
profiles has been investigated in two distinct frequency ranges using a boomer (600–2600 Hz) and an echosounder (38 kHz).
A comparison of data from both seismic sources showed strong differences in displaying reflectors. Different compressional
wave velocities were observed in acoustic turbidity zones between boomer and echosounder profiles. Furthermore, acoustic turbidity
zones were differently characterised with respect to scattering and attenuation of seismic waves. This leads to the conclusion
that seismic parameters become strongly frequency dependent due to the dynamic properties of gas bubbles. 相似文献
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Study on the Log-Linear Velocity Profile of Near-Bed Tidal Current in Estuarine and Coastal Waters 总被引：2，自引：1，他引：2
Many observed data show that the near-bed tidal velocity profile deviates from the usual logarithmic law. The amount of deviation may not be large, but it results in large errors when the logarithmic velocity profile is used to calculate the bed roughness height and friction velocity （or shear stress）. Based on their investigation, Kuo et al. （1996） indicate that the deviation amplitude may exceed 100%. On the basis of fluid dynamic principle, the profile of the near-bed tidal velocity in estuarine and coastal waters is established by introducing Prandtl＇ s mixing length theory and Von Kannan selfsimilarity theory. By the fitting and calculation of the near-bed velocity profde data observed in the west Solent, England, the results are compared with those of the usual logarithmic model, and it is shown that the present near-bed tidal velocity profile model has such advantages as higher fitting precision, and better inner consistency between the roughness height and friction velocity. The calculated roughness height and friction velocity are closer to reality. The conclusions are validated that the logarithmic model underestimates the roughness height and friction velocity during tidal acceleration and overestimates them during tidal deceleration. 相似文献
6.
Gil Young Kim Gwang Soo Lee Dong Geun Yoo Young Kyo Seo Im Hak Kim 《Marine Georesources & Geotechnology》2018,36(3):264-270
The KISAP (Korea Institute of Geoscience and Mineral Resources Seafloor Acoustic Probe) was developed to obtain in situ compressional wave velocity and attenuation profiles for seafloor sediments. The instrument comprises recording channel receivers, and an acoustic source, and can be attached to a corer or a probe. Here, we report experiments comparing KISAP in situ velocity to laboratory velocity of colocated piston cores. KISAP data matched laboratory data (corrected for temperature and pressure) reasonably. KISAP can be used to collect in situ acoustic data and can be effectively used to calibrate previous laboratory data to in situ data. 相似文献
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Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform. 相似文献
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时深转换是将地震资料解释成果转化为地质成果的一个重要环节,以油田勘探实际资料为例针对几种不同的时深转换方法进行深入讨论.对于常速成图分区分深度进行幂函数拟合是最理想的办法,对于变速成图在实际应用中需根据不同的资料特征和实际情况选用不同的变速成图方法.通过变速成图计算误差的对比阐述各种方法的优缺点和适用范围,进而根据不同的地质及地震反射条件,选择合适的时深转换方法,以达到最佳的地质成果. 相似文献
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P-Vector Spirals and Determination of Absolute Velocities 总被引：3，自引：0，他引：3
Peter C. Chu 《Journal of Oceanography》2000,56(5):591-599
A simple method to invert the absolute geostrophic velocity on potential-density surfaces is developed based on McDougall's (1988) conservation statements on potential-density surfaces and Chu's (1995) and McDougall's (1995) P-vector concept. This method has a capability to handle a system with diapycnal velocities and non-coincidence of potential-density and neutral surfaces. The validity of the inversion is the existence of the P-vector spirals instead of the existence of the velocity spirals (usually called the -spirals). We use a climatological T,S dataset for the Atlantic Ocean from the National Oceanographic Data Center (NODC) to show the benefit of using P-vector spirals in inverting the velocity field. 相似文献
12.
基于哨兵一号和高分三号卫星SAR数据的马六甲海峡内孤立波特性研究 总被引：2，自引：0，他引：2
漫长狭窄的马六甲海峡是重要的航道，研究该海峡内孤立波特征对潜艇、船只航行和海洋工程都是急需解决的问题。利用高空间分辨率的哨兵1号（Sentinel-1）和高分三号（GF-3）SAR遥感数据，对马六甲海峡的内孤立波特征开展了详细研究。利用哨兵一号2015年6月到2016年12月20景有内孤立波的SAR图像和高分三号2018年4月到2019年3月24景有内孤立波的SAR图像，统计分析了马六甲海峡海域的内孤立波空间分布特征。发现内孤立波多以内孤立波包以及单根内孤立波形式出现，内孤立波头波的波峰线最长可达39km。采用高阶非线性薛定谔方程反演模型可以计算出内孤立波的振幅与群速度，计算得到的内孤立波振幅和波包的传播群速度分别为4.7m ~ 23.9m和0.12m/s ~ 0.40m/s。由KdV方程得到的单根内孤立波的相速度为0.26m/s ~ 0.60m/s。可以得到，马六甲海峡内孤立波的振幅与传播速度与地形密切相关。 相似文献
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M.S. Fonseca J.S. Fisher J.C. Zieman G.W. Thayer 《Estuarine, Coastal and Shelf Science》1982,15(4):351-364
A salt-water flume was used to describe the mechanics of current flow around an articial Zostera marina meadow. Shear velocity and roughness height were positively correlated with seagrass surface area, and were positively/negatively correlated with current velocity. Current velocity intrusion into the meadow before diminution and maximum reduction (both at the 2 cm height line) proceed by factors of 1·25 and 2·07 cm into the meadow per cm s?1 of current velocity, respectively.Froude number was correlated with mean bending angle of the canopy as a whole. Maximum bending had occurred with Froude = 1, but most bending had taken place by Froude = 0·4, a velocity of 40–50 cm s?1 in this experiment.The meadow edge is the most dynamic zone of a seagrass meadow in regard to current flow. Bending of the shoot canopy is a mechanism for re-direction of current flow and in-canopy reduction of current velocity. Meadow dimensions may be regulated by scouring processes in different hydraulic regimes. Shoot bending and subsequent in-meadow current velocity reduction are mechanisms that affect self-shading and photosynthetic capabilities as well as providing habitat stability. 相似文献
14.
《Marine Geodesy》2013,36(3-4):355-366
Sea surface slope computed from along-track Jason-1 and TOPEX/POSEIDON (T/P) altimeter data at ocean mesoscale wavelengths are compared to determine the equivalent 1 Hz instrument height noise of the Poseidon-2 and TOPEX altimeters. This geophysical evaluation shows that the Ku-band 1-Hz range noise for both instruments is better than 1.7 cm at 2 m significant wave heights (H1/3), exceeding error budget requirements for both missions. Furthermore, we show that the quality of these instruments allows optimal filtering of the 1-Hz along-track sea surface height data for sea surface slopes that can be used to calculate cross track geostrophic velocity anomalies at the baroclinic Rossby radius of deformation to better than 5 cm/sec precision along 87.5% of the satellite ground track between 2 and 60 degrees absolute latitude over the deep abyssal ocean (depths greater than 1000 m). This level of precision will facilitate scientific studies of surface geostrophic velocity variability using data from the Jason-1 and T/P Tandem Mission. 相似文献
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速度分析是地震数据处理中的重要环节之一,基于各向同性假设的传统速度分析技术已经被广泛应用,但是地下地质体存在不同程度的各向异性,而且现代海洋地震勘探逐步向深层勘探发展,拖揽长度不断增加,使得地层各向异性问题日益突出。通过对琼东南海域进行高密度各向异性速度分析技术的应用,同时扫描得到速度和各向异性参数,提高了速度分析的密度和精度,解决了远偏移距无法拉平问题,改善了地震资料成像质量。 相似文献
16.
近二十多年,盐沼水-沉积物-植物界面流速的研究取得了很大的进展。本文拟对盐沼水-沉积物-植物界面的流速分布、变化和研究状况进行一定的归纳,并提出可能的研究方向和途径。本文内容包括通过野外观测和室内模拟定量分析研究盐沼和不同植被状况下(不同植株高度、密度、不同种类植株等)流速变化规律,及其流速变化原因。 相似文献
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盐沼水-沉积物-植物界面流速研究进展 总被引：2，自引：0，他引：2
综述了近20多年来盐沼水-沉积物-植物界面流速的研究进展。在此基础上,拟对盐沼水-沉积物-植物界面的流速分布、变化和研究状况进行一定的归纳,并提出可能的研究方向和途径。内容包括通过野外观测和室内模拟定量分析研究盐沼和不同植被状况下(不同植株高度、密度、不同种类植株等)流速变化规律及其流速变化原因。本领域研究有待收集大量数据后进一步深入和系统地探讨。 相似文献
18.
Sea surface slope computed from along-track Jason-1 and TOPEX/POSEIDON (T/P) altimeter data at ocean mesoscale wavelengths are compared to determine the equivalent 1 Hz instrument height noise of the Poseidon-2 and TOPEX altimeters. This geophysical evaluation shows that the Ku-band 1-Hz range noise for both instruments is better than 1.7 cm at 2 m significant wave heights (H1/3), exceeding error budget requirements for both missions. Furthermore, we show that the quality of these instruments allows optimal filtering of the 1-Hz along-track sea surface height data for sea surface slopes that can be used to calculate cross track geostrophic velocity anomalies at the baroclinic Rossby radius of deformation to better than 5 cm/sec precision along 87.5% of the satellite ground track between 2 and 60 degrees absolute latitude over the deep abyssal ocean (depths greater than 1000 m). This level of precision will facilitate scientific studies of surface geostrophic velocity variability using data from the Jason-1 and T/P Tandem Mission. 相似文献
19.
Wei Shoulin Xiao Rong Professor Ocean University of Qingdao Qingdao . Teaching Assistant Ocean University of Qingdao Qingdao 《中国海洋工程》1994,(1)
- In this paper, a numerical computation method is developed for the computation of current field in the tidal zone, using the well-point method and ADI method. The computational results agree well with the general variation of current field in the tidal zone. 相似文献
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Comparison of Kuroshio surface velocities derived from satellite altimeter and drifting buoy data 总被引：2，自引：0，他引：2
Sea-surface geostrophic velocities for the Kuroshio region calculated from TOPEX/POSEIDON altimetry data together within situ oceanographic data are compared with surface velocities derived from drifting buoy trajectories. The geostrophic velocities
agree well with the observed velocities, suggesting that the Kuroshio surface layer is essentially in geostrophic balance,
within measurement error. The comparison is improved a little when the centrifugal acceleration is taken into account. The
observed velocities are divided into the temporal mean and fluctuation components, and the partitioning of velocities between
these two components is examined. For the Kuroshio region, most of the fluctuation components of the velocities derived from
drifting buoys are found to be positive. This result suggests that Eulerian mean velocities for the Kuroshio region estimated
from drifting buoy data tend to be larger than actual means, due to the buoy’s tendency to sample preferentially in the high-velocity
Kuroshio. 相似文献