均匀层浅海声场与海底反射损失的关系

海底对浅海声传播的影响很大。海底有复杂的多层结构。在计算声场时如果把多层海底的影响都考虑进去,就会使计算复杂化,得不出一个清晰的物理图象。因此,在计算中往往使用海底反射损失系数来代替多层海底的模型。但海底反射损失与角度有复杂的依赖关系。为了计算方便,提出过不少简化模型。已经使用的模型有反射损失与角度无关、与角度一次方成正比;后来又提出反射损失在某一临界角之下与角度一次方成正比,在临界角之上与角度无关的三参数模型,克服了远场与近场衔接的问题[1,2]。但这些模型不一定在所有情况下都能反映海底反射损失与角度的关系的主要特征。本文提出一个近似方法,可以计算海底反射损失按任意规律随角度单调上升的情况下的声场。     

浅海简正波数值声场

本文讨论了在给定海底界面反射参数时,浅海声场简正波本征函数,实本征值,归一因子及筒正波指数衰减因子的数值计算方法,对于高声速海底,给出了由P、Q两个参数描写的小掠射角反射特征的简正波声场数值程序,在程序中采用了“两步分选及黄金分割法”的技巧,最后,文中给出了计算实例以及与实验结果的初步比较。     

基于FIO-COM的海洋声学预报系统的构建与应用

将海洋模式与声传播模型结合在一起,设计开发了一种适用于高性能计算机的全球海洋声学预报系统FIO-GOAFS,该系统以自然资源部第一海洋研究所全球0.1°分辨率海浪-潮流-环流耦合模式（FIO-COM）为基础,利用海洋模式预报的温、盐、深参数计算声速剖面,并对声速剖面进行水声环境特征诊断,之后将海洋模式与水下声场传播模型协同连接,结合地声模型（海底地形和底质参数）,实现了全球海域的水声环境特征诊断及水下声场及相关结果的预报。海洋模型提供水下声学预报所需的水体声速、海浪波高等参数,地声模型提供海底地形、底质声速、密度以及衰减等参数,通过调用海洋-声学连接模块提取声传播路径的地形及海洋环境参数剖面,实现海洋模型和声学模型的有效连接。全球海洋声学预报系统在高性能计算机上并行实现,主要包括声场计算中的频点、方位角并行以及声学预报时针对地理空间区域的并行。最后,利用该系统预报并分析了全球海域的水声环境特性及声呐作用距离的季节变化和空间分布特征,为现代声呐的设计、操作和水下应用提供参考。     

浅海大陆架地声模型的海底反射特性

海底的声反射特性的研究近年来受到极大的注意,并取得迅速的进展。这主要是:(1)海洋声场的预报和分析必须对海底反射性能有足够的了解;(2)利用声波与海底的相互作用,有可能把声波作为一种遥感海底特性的有效手段。因此,在“声学海洋学”中海底声反射特性成为主要的课题。     

低声速海底反射损失的测量

在浅海声场分析中，海底反射系数是个重要参数。近20年来，国外由于浅海声场预报及声纳研制的需要，做了大量关于海底反射损失的实验。最早的海底反射系数的测量工作是由Lieberman[1]等人做的。有关沉积层的声学特性方面的大量测量工作是Hamilton和Hampton等人做的[2-5]。     

低声速海底反射损失的测量

海底反射损失是分析浅海声场的重要参数之一，本文用爆炸声源在水深为150米的低声速底的湖中进行底的反射损失测量。于100Hz到5KHz分析了反射损失与掠射角的关系，并讨论了它们与底沉积物孔隙率、     

浅海沉积声学原位探测系统研制及深海功能拓展

海底沉积物的声速和声衰减系数等声学特性参数是影响水下声场空间结构、水声通讯、水声设备使用性能、海底目标探测的重要因素。介绍了最新研制的浅海海底沉积声学原位测量系统的工作原理、结构组成和性能特点,并对系统在黄海和南海海底沉积物声学特性调查中的应用情况进行了总结。最后,对系统在满足深海应用方面的功能拓展进行了讨论和展望。     

南海三海区海底沉积物物理性质及声学特性

海底是影响海洋声场极其重要的环境因素。了解海底沉积物的物理特性以及它与声学参数的关系,对于海洋声场分析,声纳作用距离的预报,水声设备在海洋中检测和应用等等都是必不可少的。出于实用的需要,我们曾于夏季在二十天时间内对南海三个海区水声环境场进行考察,其中海底沉积物的物理特性和声学特性是主要内容之一。分别标称为Ⅰ、Ⅱ、Ⅲ的三个海区同在一个海域,都处于纬度18°40N＇上下,距离海岸Ⅰ海区约5n mile,Ⅱ海区50n mile,Ⅲ海区110n mile左右,考察范围,每个海区约200     

浅海沉积层声学特性对声传播损失的影响仿真研究

为厘清海底沉积层声学特性信息的水声环境保障需求,构建浅海两层海底环境参数模型,并参考Hamilton海底底质9种分类设置沉积层声速、密度、衰减系数及厚度的参考值及计算采样区间,利用Kraken简振波模型,采用控制变量的方法,研究了浅海沉积层声学特性参数对声传播损失的影响;开展了建模理论推导及数值技术分析,研究了海底沉积层声学特性参数在模型计算过程中调用过程,并从建模计算的角度对仿真计算的结果进行解释,对海底沉积层声学特性调查装备发展及调查重点参数具有一定的参考价值。     

浅海均匀层远程混响的垂直相干性

混响是主动声纳在浅海环境中的一种干扰,有关其空间相关特性,Urick和Lund发表了两篇实验性报告[7].本文根据浅海平均声场角度谱分析法[3],从理论上计算了浅海均匀层远程混响垂直相关特性与界面反射、散射等环境参数之间的关系,及其随距离、水听器间隔的变化,供声纳设计或在浅海环境中研究低频、小掠角的散射特性时参考.     

南海海面风速季节特征的卫星遥感分析

利用ＧＥＯＳＡＴ卫星高度计于１９８６年１１月至１９８９年３月;司所测的南海海面风速资料,统计分析了南海海面风速的统计特征以及海面风场的分布特点。分析结果表明：南海海区风速受各种天气系统（如季风、台风、副热带高压等）的影响显著,表现为春、夏、秋季平均风速较小,冬季较大,风场分布呈现出夏季南部大,北部小,其他季节为由南向北增强的分布趋势,并在１０°Ｎ,１１０°Ｅ附近海区各季都有一较为稳定的高风速区,其范围大小和中心位置随季节略有变化。     

Comments on the “shear effect” and diffusion in the Lagrangian framework

We indentify three different types of Lagrangian coordinate systems that are used in oceanography. These are: true Lagrangian coordinates (TLC), Lagrangian coordinates (LC), and averaged Lagrangian coordinates (ALC). The diffusion process is studied in each of these coordinate systems. At large scales the eddydiffusivity is proven to be independent of molecular diffusivity, providing the spectrum of turbulent kinetic energy varies as scale raised to a power less than 4 1/3. The shear effect is examined using solutions to the averaged Lagrangian diffusion equation obtained by Okuboet al. (1983). In Eulerian coordinates both advection and diffusion are necessary for the occurrence of the shear effect, while in ALC timedependent dispersion coefficients are necessary for the process. In TLC we use the method of Taylor (1921) to study the dispersion of material by a velocity field, that from the Eulerian perspective, consists of turbulent motion across a uniform shear. The transformation of the above Eulerian velocity field into TLC results in a uniform deformation field and turbulent motion both along and across the shear. This work shows how dispersion of material is related to the turbulent Eulerian velocity and uniform velocity gradients. The instantaneous rate of change of variance of a spreading patch of material is completely specified by the instantaneous divergence obtained over the area occupied by the patch (Kawai, 1976). This relationship is shown to depend upon the fact that at any particular instant it is possible to define TLC that are equivalent to the Eulerian coordinates. In order to describe patch spreading from divergence measured over longer periods it is also necessary to consider other dispersive processes.Contribution number of the Newfoundland Institute of Cold Ocean Science.     

Study on short-range numerical forecasting of ocean current in the East China Sea Ⅱ. Three-dimensional diagnostic model and its application in the Bohai Sea

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Investigation into wave properties of the atlantic surface temperature spatial variability on interannual scales

The results of investigations into the spatial variability of the Atlantic Ocean surface temperature field on interannual scales are presented. The analysis is based on monthly mean satellite data of the AVHRR Pathfinder Data JPL NOAA/NASA over 1985–2001. Specific features of the structure of the sea surface temperature (SST) fields averaged over 17 years, as well as fields of the gradient and variance of the SST time series, are described for each node of the data grid. It is shown with the use of the rhythmodynamic approach that spatial heat waves exist in the interannual variability of the SST field in two directions: zonal and meridional.     

Contribution of breaking internal waves to structure formation,energy dissipation,and vertical diffusion in the ocean

The relationship between the scale of the spectral minimum of the first differences in temperature fluctuationsL and the local value of the Väisälä-Brunt frequencyN has been analysed using the results of more than 600 soundings made in various regions of the world's oceans. Allowing for the series of theoretical and experimental indications of the fact that the vertical scaleL at the boundary between the fine structure and microstructure in the ocean exists under the effect of processes of breaking of internal waves and hydrodynamic instability with the formation of turbulent patches, and using the energy relationships, the relationship for a solitary patch has been derived through the determining parameters. Based on two expressions forL, derived experimentally and using the energy estimations, the relationships for the averaged rate of absorption of the wave field energy by patches and the coefficient of the density vertical diffusion are derived, which do not contradict a series of independent estimations fromin situ measurements.Translated by Mikhail M. Trufanov.     

具有随机起伏表面的正声速梯度浅海中的平均声强

近年来很多的实验指出,正声速梯度浅海中声强的平均衰减规律与海面的不平整度,声波的频率,相对声速梯度的大小,发射深度与接收深度等因素有着密切的联系.本文的目的在于寻找这种联系的数学表式.我们采用文献[1]所发展的平均法来求其平均声强.     

两个同源地不同路径热带气旋的大尺度场对比分析

本文利用NCEP/NCAR再分析格点资料,着重对8903号"BRENDA"和0601号"珍珠"两个同源地进入南海后不同路径的典型热带气旋的大尺度环境场进行对比分析。结果表明:西风槽的强弱和东移的快慢、西太平洋副高的形状变化和东退西进、冷空气的强弱和南下路径及热带气旋内部的不对称结构是造成二者移动路经差异的主要原因。另,印缅槽的变化也对其路径差异有一定的作用。     

Baroclinic pressure gradient difference schemes of subtracting the local averaged density stratification in sigma coordinates models

Much has been written of the error in computing the baroclinic pressure gradient (BPG) with sigma coordinates in ocean or atmos- pheric numerical models. The usual way to reduce the error is to subtract area-averaged density stratification of the whole computa- tion region. But if there is great difference between the area-averaged and the local averaged density stratification, the error will be obvious. An example is given to show that the error from this method may be larger than that from no correction sometimes. The definition of local area is put forward. Then, four improved BPG difference schemes of subtracting the local averaged density strat- ification are designed to reduce the error. Two of them are for diagnostic calculation (density field is fixed), and the others are for prognostic calculation (density field is not fixed). The results show that the errors from these schemes all significantly decrease.