WRF模式空间分辨率对南海台风模拟的敏感性分析

为准确模拟南中国海台风路径和强度,对建立的WRF模式开展水平和垂向网格分辨率的敏感性分析。水平网格分辨率分别采用5 km,10 km,20 km,30 km以及15 km和5 km的嵌套方案等5种情况,垂向网格分辨率采用35层、28层和20层等3种情况,顶部最大压强采用1000 Pa,2000 Pa,3500 Pa和5000 Pa等4种情况,针对台风"启德"的路径和强度进行模拟分析。对不同条件组合下的台风路径、风速和海面压强进行对比,发现水平和垂向网格分辨率对台风路径的影响比较有限,对台风强度的影响相对显著。基于高精度空间分辨率模拟得到的台风强度与实测值吻合更好,采用嵌套网格技术对计算结果精度的提高效果显著。采用35层的垂向分辨率得到的模拟结果明显优于基于20层和28层得到的模拟结果。经过对比分析,确定适用于本研究的最优参数设置：水平空间分辨率采用15 km和5 km的双向嵌套网格方案;垂向分层为35层,顶部最大压强为2000 Pa。     

测井约束的海洋CSEM反演及其在南黄海中部隆起区勘探应用

海洋可控源电磁法(Controlled-Source ElectroMagnetic,CSEM)对于油气储藏饱和度判别具有较高的敏感性,这为其用于油气储藏检测奠定了基础.但是海洋CSEM相较于地震勘探而言对异常体的垂向分辨率较低,这为海洋CSEM资料反演异常体垂向结构带来困难.由于测井数据具有垂向分辨率高的特点,蕴含丰...     

南海温跃层深度计算方法的比较

基于1986-2008年的中国近海及邻近海域再分析产品(CORA)气候平均海温资料,分别运用S-T法、垂向梯度法和最大曲率点3种温跃层定义计算了南海温跃层上界深度,揭示了南海温跃层季节变化特征。对3种不同定义确定的温跃层上界深度进行比较发现:采用不同定义计算南海温跃层上界深度存在差异,S-T法确定的温跃层上界深度最浅,垂向梯度法其次,最大曲率点法最深;在深水区(水深200 m)运用S-T法计算的温跃层上界深度与垂向梯度法的结果比较一致,都与实际温跃层深度符合较好;在浅水区(水深200 m),垂向梯度法和最大曲率点法可以准确判定无跃区,但对于温跃层深度计算,3种定义误差均较大。     

多波束探测分辨率估计模型研究

多波束探测分辨率是衡量多波束探测能力的重要指标,针对如何确定多波束探测分辨率这一问题,通过原理分析,阐述了多波束探测分辨率的含义,在几何空间上推导了纵向、横向和垂向分辨率估计模型,提出了多波束目标探测分辨率模型,并以Reson 8101多波束测深仪为例进行了计算。计算结果表明,该模型能较直接地估计多波束探测分辨率,可作为多波束测量技术设计的重要依据,同时发现多波束探测横向分辨率是多波束目标探测分辨率的主要决定因素。     

长江口底部边界层细颗粒泥沙过程

1连续的、高时空分辨率的河口细颗粒悬沙浓度垂线分布在长江口深水航道北槽,利用"声学是沙观测系统"观测到大潮典型的高时空分辨率细颗粒是沙浓度声学垂向分布图和垂线分布曲线。研究结果表明：（1）在涨潮时呈L形,是沙浓度的垂向变化梯度小（浓度小于1.0gL－1）。（2）在涨急时呈射流形,射流项悬沙浓度达10gL-1,悬沙浓度的垂向变化梯度大。（3）在接近涨想时,是沙浓度的垂向梯度小。（4）在落潮时从水面到水底是沙浓度按指数增加,代表恒定均匀流中悬沙处于平衡条件的分布,泥沙垂向扩散系数。在数值上大约是泥沙颗粒沉降速度Ws的两…     

eSQG方法在南海垂向流速诊断中的应用研究

本文利用OFES模式0.1°×0.1°高分辨率温盐、流速和海面高度（SSH）数据,分析eSQG方法在南海垂向流速诊断中的适用性和南海垂向流速的时空变化特征。结果表明,基于SSH和eSQG的诊断垂向流速ω_eSQG与OFES模拟“真值”垂向流速ω_OFES整体量级基本相当,为O（10?5 m/s）,空间上呈现北强南弱。深海盆（水深大于1 000 m）ω_eSQG与ω_OFES的水平空间分布的相关系数rs在次表层150 m左右达到最大,高于南海全海域的空间相关系数,表明eSQG在远离边界的深水区更有效。季节上,ω_eSQG总体夏强冬弱,与ω_OFES的相关系数rs冬季大、夏季小,表明eSQG更适用于冬季南海垂向流速的诊断。eSQG诊断垂向流速在台湾西南部和越南以东适用性更高,与ω_OFES的时间相关系数rt超过0.6;海盆南部和西北部陆架区诊断效果较差,时间相关系数rt多小于0.2。同一区域ω_eSQG和ω_OFES空间相关系数存在18～55 d的周期变化。分析显示,海面高度与海面密度同相位分布时,ω_eSQG与“真值”ω_OFES更接近。时间分辨率对eSQG诊断效果几乎无影响,空间分辨率降低到0.25°时rs整体增大,说明eSQG在中尺度诊断效果更好。     

不同CTD数据垂向分辨率对黑潮地转流动力计算的影响分析

基于日本海洋信息中心提供的东海黑潮PN断面垂向分辨率不同的2种CTD数据,采用动力高度法计算了2000—2011年的断面流速。通过对49个航次的流场结构、最大流速、流幅、流量等黑潮特征值的对比,分析了不同数据垂向分辨率对黑潮地转流动力计算的影响。结果表明:数据垂向分辨率不同对东海黑潮的流量几乎没有影响,对平均流幅影响很小,对流核位置略有影响,但对平均流核个数、平均最大流速影响较大。2种数据对应的流场差异主要有:与低分辨率数据对应的流场相比较,高分辨率数据对应的流场流核区流速较大、平均流核数偏多。不同流核结构在2种数据对应的流场中出现概率差别较大,低分辨率数据结果中的单核结构出现概率最高,高分辨率数据结果中的双核结构出现概率最高。     

海洋模式的水平分辨率对吕宋海峡深层环流数值模拟结果的影响

基于南海观测得到的垂向混合率修改KPP垂向混合方案,利用大洋环流模式HYCOM首次模拟得到了吕宋海峡深层环流的空间分布特征,并通过3个不同水平分辨率的实验(1/6(°)、1/12(°)、1/24(°))讨论水平分辨率对模拟吕宋海峡深层环流空间结构的影响。模拟结果表明:(1)1/6(°)水平分辨率过于粗糙,无法分辨巴士海峡和台东海峡地形特征,无法得到吕宋海峡深层环流的空间分布特征;(2)1/12(°)的水平分辨率可以很好的分辨吕宋海峡和台东海峡的地形特征,模拟得到吕宋海峡深层环流的空间分布和流场特征;(3)1/24(°)水平分辨率的模拟结果表明,更高的水平分辨率不会改变吕宋海峡深层环流的空间分布和主要出入口的垂向结构,只是会显示更细节的环流结构。1/12(°)和1/24(°)水平分辨率的模式结果都表明,西北太平洋深层水通过巴士海峡和台东海峡进入吕宋海沟,年平均流量分别为1.1和0.4Sv,然后沿吕宋海沟向南海方向流动,最后主要通过位于恒春海脊上的2个缺口进入南海,年平均流量分别为0.5和0.9Sv。     

多波束资料在胶州湾口海底节理构造研究中的应用

利用2004年5月在青岛胶州湾口获得的高分辨率多波束资料(水平分辨率0.5m×1m,垂向分辨率0.2m),研究了该区海底节理构造及其分布规律,揭示青岛胶州湾团岛至薛家岛的研究区域中存在大量线性微地形,在海底地形图上表现为2组相交的“X”型线性阴影(一组为NE向,另一组为NW向),把整个海底切割成菱形格状。结合侧扫声纳探测等资料分析,认为这种线性微地形可能代表了海底出露的节理(裂隙)微构造。     

舟山群岛附近海域三维水动力数值模拟

利用ECOM模型模拟了舟山群岛附近海域流场和三维水动力特征,研究综合考虑了长江、钱塘江径流以及垂向温盐变化引起的斜压效应。考虑到实际岛屿形状和海底地形,平面采用直角坐标系,垂向采用σ坐标系,使垂向沿水深的分层更趋合理。通过多个验潮站的调和常数和实测海流资料的验证,计算结果与实测结果符合良好。结果显示,舟山群岛附近海域潮汐日不等现象显著,高高潮与低高潮的潮位差值为41～77cm,至杭州湾内最大差值可达109cm;潮流日不等现象不明显,两次最大涨潮流速差值为0．5～20cm／s,平均流速差为4．9cm／s;两次最大落潮流速差值为0．5～23cm／s,平均流速差为7．3cm／s,且底层差值大于上层差值,说明研究区属于不正规半日潮汐、正规半日潮流海区。本海区最大涨潮平均流速为120～213cm／s,最大落潮平均流速在105～182cm／s之间,基本以舟山群岛为界,东侧涨潮流速大于落潮流速,西侧落潮流速大于涨潮流速。数值模拟结果基本上体现了舟山群岛附近海域的潮流场状况。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.