Spatial and temporal variability and size fractionation of chlorophyll a in the tropical and subtropical Pacific Ocean

The spatial and temporal variability and size fractionation of chlorophyll a(Chl a) were investigated in the tropical and subtropical Pacific Ocean during four survey cruises from 2005 to 2009.The surface Chl a(S-Chl a) concentration ranged from 0.002 to 0.497 mg/m 3 and was obviously higher in the eastern Pacific than in the western and central Pacific.The vertical distribution of Chl a displayed a single peak pattern,and the maximum Chl a layer(MCL) was observed at a shallower depth in the eastern Pacific than in the western Pacific.All three size fractions of Chl a measurements in the surface water showed a similar distribution to total Chl a and were found in higher concentrations in the eastern Pacific than in the western and central Pacific.Picoplankton dominated the phytoplankton in the surveyed tropical and subtropical Pacific Ocean.Furthermore,pico-Chl a(0.2-2 μm) accounted for a larger percentage of the total Chl a in the central Pacific than it did in the western Pacific and eastern Pacific.In the western Pacific,there seemed to be a latitudinal variability in the phytoplankton community composition where small-sized phytoplankton(<2 μm) were more dominant in the tropical than in the subtropical western Pacific.The spatial and temporal variability and size fractionation of Chl a were controlled by hydrological and chemical characteristics and climate events,such as El Nin o and La Nin a.     

A Lagrangian particle random walk model for simulating a deep-sea hydrothermal plume with both buoyant and non-buoyant features

This paper presents a computational model of simulating a deep-sea hydrothermal plume based on a Lagrangian particle random walk algorithm. This model achieves the efficient process to calculate a numerical plume developed in a fluid-advected environment with the characteristics such as significant filament intermittency and significant plume meander due to flow variation with both time and location. Especially, this model addresses both non-buoyant and buoyant features of a deep-sea hydrothermal plume in three dimensions, which significantly challenge a strategy for tracing the deep-sea hydrothermal plume and localizing its source. This paper also systematically discusses stochastic initial and boundary conditions that are critical to generate a proper numerical plume. The developed model is a powerful tool to evaluate and optimize strategies for the tracking of a deep-sea hydrothermal plume via an autonomous underwater vehicle (AUV).     

中国热带6种海参骨片的种类和形态研究

利用扫描电子显微镜对我国6种热带海参(蛇目白尼参、玉足海参、花刺参、梅花参、子安辐肛参和巨梅花参)背脊部骨片的组成和结构进行了观察。结果表明,蛇目白尼参骨片有3种类型的花纹样体和1种杆状体;玉足海参骨片有2种类型的桌形体和1种扣形体;花刺参骨片有2种类型的桌形体、1种C形体和1种花纹样体;梅花参骨片有4种类型的杆状体;子安辐肛参骨片有1种花纹样体;巨梅花参骨片有1种杆状体、1种拟桌形体和1种颗粒体。结果显示,与之前学者光镜下观察的结果存在差异,玉足海参桌形体底盘中央是单孔而非4孔;花刺参桌形体立柱之间没有横梁连接。并发现了新的骨片类型:蛇目白尼参Ⅲ型花纹样体和杆状体;玉足海参顶部周缘小孔桌形体;花刺参顶部5簇小齿桌形体;梅花参Ⅱ型、Ⅲ型、Ⅳ型杆状体。     

Transient soil response in a porous seabed with variable permeability

The soil permeability of many natural marine sediments decreases with depth because of consolidation under overburden pressure. This is accompanied by a decrease in porosity and void ratio that also affect the permeability. Conventional theories for wave-induced soil response have assumed a homogeneous porous seabed. This paper presents a new approach for the wave-induced response in a soil matrix, with variable permeability as a function of burial depth. The soil matrix considered is unsaturated and anisotropic, and is subject to a three-dimensional wave system. The pore pressure and effective stresses induced by such a system are obtained from a set of equations incorporating a variable permeability. Verification is available through reduction to the simple case of uniform permeability. The results indicate that the effect of variable soil permeability on pore pressure and vertical effective stress may be significant, especially in a gravelled seabed and for unsaturated sandy soils.     

AEL—1型风向,风速仪

本文介绍并叙述了AEL-1型风向、风速仪的设计原理,仪器各部分的电路设计,工作过程及系统软件。该仪器适用于气象台站、工矿企业、海上浮标及科研单位等部门。     

EPSONDE: an instrument to measure turbulence in the deep ocean

EPSONDE is a tethered free-fall profiling system used to obtain temperature microstructure and velocity turbulence data to a depth of at least 1500 m. EPSONDE, which carries a variety of slow and fast sensors, is deployed on a loose kevlar multiconductor cable by a specialized wire-handling system. Data are transmitted from this underwater unit (1792 samples per second) to a shipboard system which includes a dedicated microcomputer for data logging and online data processing. The performance of this system is demonstrated by discussing a study of turbulent mixing processes in a lens of Mediterranean water (a MEDDY) found at a depth of 1000 m in the Canary basin. These studies indicate that turbulent kinetic energy dissipation may be an important mechanism in determining the decay and lifetime of a MEDDY     

Algorithm for non-hydrostatic dynamics in the Regional Oceanic Modeling System

A non-hydrostatic algorithm for the Regional Oceanic Modeling System (ROMS) is proposed. It is based on a decomposition technique for hydrostatic and non-hydrostatic pressure. The algorithm has a pressure-correction scheme with split-explicit time-stepping for baroclinic and barotropic vertical modes with a free surface. The algorithm implementation requires solving a Poisson equation for a non-hydrostatic pressure that has a non-symmetric matrix in discrete form. The efficiency of a different class of solvers and preconditioners were tested. The algorithm is successfully implemented with several examples where non-hydrostatic effects are important. These include standing external gravity waves; strongly nonlinear internal wave generation and transformation; stratified shear instability and its associated mixing; and nonlinear internal tidal generation over a ridge. The corresponding changes in the pre-processing and post-processing infrastructure in the existing hydrostatic ROMS code were performed to implement parallel elliptic solvers and a new set of dynamical equations.     

黎安港海水和沉积物中叶绿素a含量及与环境因子的关系分析

在2019年6月和9月对黎安港海域9个站点进行水质和沉积物采样调查,研究叶绿素a含量在潟湖内的空间分布,并探讨叶绿素a含量与相关环境因子的关系,为黎安省级海草特别保护区的海草资源保护与恢复提供基础数据及理论研究.结果表明:水体叶绿素a含量时空分布不均匀.6月,水体叶绿素a含量变化范围为3.34μg/L?14.64μg/...     

与岸线协调的水深自动选取方法

针对当前水深自动选取中水深点与岸线的协调匹配问题,提出了一种与岸线协调的水深自动选取方法。通过分析资料水深点与岸线的平面位置关系,提取出与岸线协调的待选水深点;从航海安全角度考虑,优先选取浅水深点;在此基础上,分别定义水深点与岸线弯曲处、平直处的协调度,并建立协调度评估模型;通过定量计算协调度,选取出与岸线协调匹配的水深点。实验结果表明,所提方法能在岸线弯曲处优先选取出协调的水深点,同时能保证在岸线平直处附近所选取的水深点分布合理;所提方法能够较好地考虑水深点与岸线的图上位置关系,避免水深注记中断岸线、水深注记"上陆"的情况出现。     

南海叶绿素a浓度垂直分布的统计估算

分析整理了1993—2006年近10 a南海北部海域、南沙海域和南海其他海域的叶绿素a浓度历史航次调查资料,基于前人提出的全球叶绿素浓度垂直分布的统计分析模式,根据南海表层叶绿素a浓度大小的不同分级,对南海叶绿素a浓度进行了参数化处理,拟合估算了南海各水层剖面的叶绿素a浓度分布值,并结合不同海区的环境特征,分析了南海叶绿素a浓度垂直分布与其海水物理环境的关系。初步分析结果表明,叶绿素a浓度随深度垂直变化的拟合曲线呈一定倾斜的正态分布特征,当表层叶绿素a浓度较低时,作为南海深水海盆区的代表,拟合值更接近实测平均值的分布,叶绿素a浓度高值集中在次表层剖面上;当表层叶绿素a浓度较高时,作为近岸区和河口区的代表,高值多集中在表层海水,拟合误差偏大。该统计估算模式对于揭示南海叶绿素a浓度垂直分布结构进行了有益的尝试,为发展适合不同海区特点的模式以及校正参数奠定了基础。利用该模式与海洋水色卫星遥感数据有效结合,将对南海叶绿素a浓度时空分布格局的研究具有重要的意义。     

Bifurcation of barotropic flow and homogenization of potential vorticity in a rotating laboratory model

Laboratory experiments with a rotating tank confirm the bifurcation character of a barotropic flow driven by an inflow and an outflow described by Sakai (1986). The model, a circular basin with a topographic β-effect, simulates a mid-latitude oceanic feature. At a low Rossby number, stationary Rossby waves are observed which are symmetrical with a line connecting the inlet and the outlet. As the Rossby number increases, a bifurcation occurs and two kinds of vortex flows are observed. In the vortex, potential vorticity is almost uniform. In addition to the two vortex flows, a jet-like inertial flow can also be observed. In general, thre results of these experiments agree well with those of a low-order model and a numerical model.     

The motion of a 9.1 m yacht hull buoy moored in open sea

A 9.1 m yacht hull was instrumented to measure its three-dimensional motion when moored in the open sea. The hull was deployed on three occasions for a total period of about 2 months and encountered a wide range of wind-wave conditions including a strong gale. The data have been analysed to give the response for each component of motion in terms of amplitude and relative phases. The hull motion is compared spectrally to the waves observed by a nearby Waverider. The hull was found to behave as a surface-keyed buoy, with a well defined response for a wide range of conditions. The presence of a resonance in pitch and roll is evident in the data with typical rms values being 5° and 10°, respectively, for significant wave height of 5 m. From data on the mooring dynamics it is concluded that the peaks observed in the tension are a result of the viscous drag opposing the change in the catenary of the mooring and the slow drift oscillations of the buoy. This type of hull is a versatile and economical candidate as a platform for meteorological and oceanographic instrumentation.     

A digital event-recording ocean bottom seismometer capsule

The ocean bottom seismometer capsule contains a 1 Hz. vertical seismometer and triggerable or programmable digital recording system. The output of the seismometer is continuously digitized at a preselected rate of 64, 128, or 256 samples/sec. The digital data words are mixed with a time code and synchronization characters, serialized and passed through a 1536 sample shift register which acts as a delay line. The serial output bits are then encoded and recorded on a SONY TC800B tape recorder which is turned on when a seismic event occurs. The event trigger occurs when the seismic signal jumps to 8 times the time averaged input signal. A memory may be programmed to run the recorder on a schedule so that small amplitude signals from refraction shots are sure to be recorded. Data are recovered using the same recorder for playback and a decoder which provides an analog output for field data interpretation or a digital output for computer analysis. An acoustic transponder allows precise ranges between the capsule and ship to be determined. In addition, commands for the capsule to release or to transmit diagnostic data may be given from the surface ship. The capsule falls freely to the ocean bottom. After a predetermined time or when a release command is received, it is released from a 68 kg steel tripod and floats to the surface. A dual timer and explosive bolt system is used to increase recovery reliability.The first capsules were designed and constructed between October 1972 and October 1973. Good results were obtained from 38 out of 43 launchings made on six expeditions in 1974, 1975, and 1976. Four capsules have been lost.     

高阶非线性完全频散性波浪数值模型及应用

为更精确地模拟强非线性完全频散性波浪的传播,采用长波上非线性重力表面波传播高阶数学模型,综合参考此模式已有的研究成果,建立了一个高达五阶的完全频散性非线性数值模型。应用该五阶模式对斜坡地形、潜堤地形及正弦沙链地形进行模拟计算,并与已有的实验资料进行对比,结果显示五阶模式较低阶模式模拟结果的精度上有了明显提高,模拟波形与实验结果吻合度良好,证明高阶模式更适用于高频散高非线性波浪传播的数值模拟。     

西藏扎布耶湖地区三万年以来的花粉记录

通过对藏北高原扎布耶湖ＺＫ２钻孔沉积物的花粉记录，揭示了该地区三万年以来植被和气候演变历史。３７３００－３６０００ａＢ．Ｐ．为森林草原植被，气候温湿，淡水湖时期；约３６０００－３１７００ａＢ．Ｐ．灌丛草原植物，气候冷干，湖水出现短暂咸化，３１７００－２０８００ａＢ．Ｐ．森林草原植被，气候温暖湿润，湖面扩大，湖水加深时期，２０８００－１４４００ａＢ．Ｐ．荒漠植被，气候冷干，湖水咸化，湖面开始缩小，初     

Demonstration of a high-frequency acoustic barrier with a time-reversal mirror

An acoustic barrier has been demonstrated using a time-reversal mirror. The experiments, at 3500 Hz, utilized a source-receiver array, a probe source collocated with a receive array, and an echo repeater to emulate a disturbance. The successful demonstration is based on the idea that a disturbance such as an object between a time-reversal mirror and its focus will significantly disturb the focal region and, in particular, the quiescent region.     

Numerical predictions of water–air wave slam using incompressible–compressible smoothed particle hydrodynamics

The high-speed impact between a body and water is an important practical problem, whether due to wave impact on a structural deck or wall, or due to a moving body such as a ship or aircraft hitting water. The very high pressures exerted are difficult to predict and the role of air may be significant. In this paper, numerical simulations are undertaken to investigate the impact of a rigid horizontal plate onto a wave crest and, in the limit, onto a flat water surface. A two-phase incompressible–compressible smoothed particle hydrodynamics (SPH) method for water and air, respectively, is applied where the water phase imposes kinematics on the air phase at the air–water interface and the air phase imposes pressures on the water at the interface. Results are compared with experimental measurements undertaken using a drop rig positioned over a wave flume so that a horizontal plate impacts the water surface in free flight. Numerical predictions of impact pressure are quite accurate; air is shown to have a significant cushioning effect for impact on to flat water and this reduces for waves as the ratio of wave height to wavelength increases.     

Design Research on Drive System of Underwater Tapping Machine

The underwater tapping machine is composed of a center bit,a tapping cutter,a sesl box,a main drive box,aboring bar assembly,a envelop,a gear case,a counter and so on.The drive system in underwater tapping machine consists of a worm drive,a gear drive system and a screw drive.The worm drive is in the main drive box.The worm is connected with a hydraulic motor and driven by the hydraulic motor.The gear drive system is a combined gear train which is the combinations of the fixed axes and differential gear train in the gear case.On the one hand,by means of the fixed axes gear trains the turn and power of transmission shaft are transferred to the boring bar and the screw rod,causing differential tam between the boring bar and the screw rod.On the other hand,the turns of the boring bar and the screw rod are transferred to the differential gear train.The differential gear train is used to drive a special counter to count axial travel of the boring bar.The screw drive is composed of a feed screw and a nut on the boring bar.There is the differential turn between the boring bar and the feed screw.By means of the nut,the boring bar can feed automatically.With the movement of the sliding gear 7 in the gear case,the designed drive system can also be provided with the ability of fast forward and fast backward movement of the boring bar in its idle motion,restdting in the increase of the tapping efficiency.     

Measuring capital value in a commercial fishery: A distance function approach

The term “overcapitalized” is frequently used to describe the condition of various fisheries, and to explain why a fishery is in poor condition from a stock status perspective. Often, the concept of overcapitalization is associated with the number of active vessels in a fishery. Although vessel counts are important, they do not fully capture investment or disinvestment in a fishery, and only serve as a crude proxy for a richer concept of fishing capital. A better measure to judge whether overcapitalization is occurring would be the change in capital value for vessels operating, or permitted in a fishery, relative to a benchmark value. Unfortunately, data do not always exist to measure vessel value and associated changes through time. This study presents a method for calculating vessel capital value using a distance function, publicly available vessel sale price data, and non-parametric programming methods. Estimates of value for vessel attributes returned by the distance function are then used to estimate a total value for currently permitted vessels in the northeast region of the United States, and to construct a capital value index for vessels active in the squid, mackerel and butterfish (SMB) fishery between 1996 and 2016. Findings show that the total value of commercially permitted vessels in the northeast region is estimated to be between $606.6 and $769.7 million ($2016). Based on the constructed capital value index, the SMB fishery has undergone a period of disinvestment marked by both declining vessel numbers and capital value.