POM模式边界条件的数值试验及其在环台湾岛海域风生流模拟中的应用

通过一个数值试验，对运用POM模式做风生流模拟时边界条件的选取方案做了初步的讨论。试验表明，POM“外模式”采用辐射边条件、“内模式”采用辐射方案的改进形式是一种可行的方法：如果用水位作为控制条件，也可以使用辐射边条件。文章同时给出了环台湾岛海域冬、夏风季生流的模拟结果。     

海洋中测温传感器的误差及其补偿方法

现代海洋仪器正向连续自动记录和自动化方面发展着。目前，电测式的海洋温度测量仪器，大都是由测温传感器、探测电缆和自动记录的二次仪表组成。     

永久性气压简表的制作及误差分析

1 前言微机已被台站在测报工作中普遍运用,但微机在运行过程中难免出现各种故障,微机出现故障在目前无备用微机的情况下,各种观测数据将要人工进行查表得出其结果,一般观测数据台站都有一个固定长期使用的表格进行查算,而气压则根据每支气压表的器差、测站伟度及气压表象牙针拔海高度计算出一个与气压表相对应的气压简表,台站每三年需检定更换一次气压表,由于更换气压表时各气压表的器差不同使原气压简表不能继续使用,需重新制作气压简表,当气压表的器差不是一个时,气压简表制作更加麻烦,并在实际工作中量出差错,制作一个     

海洋测量交叉点误差分析(一):交叉点误差的确定

海洋测量中的交叉点误差反应了测量的误差信息,交叉点误差分析是海洋测量数据处理的重要环节。首先对可能引起交叉点误差的误差源进行了分析,然后讨论了从交叉点误差分析中可能提取的信息,最后对数据连续化过程中交叉点的定位与交叉点误差的确定进行详细分析。研究发现在进行数据连续化以定位交叉点的过程中,交叉点处测量值的误差特性将不同于原始测量值的误差特性,而且不同交叉点误差之间可能存在相关性。导出了交叉点误差方差以及不同交叉点误差间协方差的公式,从而能够求得交叉点误差向量的方差协方差矩阵,该矩阵在后续的平差处理中具有重要作用。     

海洋磁力梯度测量的误差源分析

简要介绍了海洋梯度测量的发展现状。将影响梯度测量的误差主要分为四种:系统误差、航向磁效应、几何效应、波浪噪声及传感器运动误差。对每一种误差的形成原因及对梯度测量的影响进行分析,得出了一些有益的结论。     

降低受信仪行程开关返程误差方法的分析

由于受信仪的行程开关返程误差较大,导致了运行、射界范围的控制精度不高。 针对返程误差偏大实际问题,研究了受信仪的行程开关工作原理,建立了其工作过程数学模型,采用复合形法开展了参数优化设计。 依据 PDCA 程序,应用因果图分析方法获得影响误差的主要因素,并逐一采取相应的解决措施。 经过验证,其实现了凸轮行程开关的返程误差减小到 0. 5°以下,提高了发射装置运行、射界范围的控制精度,达到了预期的目标。     

夏季南黄海风漂流的不同计算方法的对比分析

分别用Ekman有限深海风漂流计算公式,普林斯顿海洋模式（POM）数值计算了南黄海风漂流。通过对这两种方法的计算结果的对比分析得出：在水深较小时,模式计算的风漂流场与公式计算结果较为接近;而在水深较大时公式计算所得风漂流场与实际流场相差较大,模式计算的风漂流场则基本再现了夏季南黄海的环流结构;风速越大,两种计算方法所得的流场之间的差别越大。同时从数值试验的角度还得到夏季由于风速普遍偏小,风场对环流结构的影响都相对较小,热盐效应是控制夏季环流的主导因素。但当风速增大到一定程度时,环流结构会发生根本改变。     

测量仪器的误差和准确度

仪器的误差是仪器质量的最重要的技术指标之一。测量仪器的误差概念和准确度的概念是相互关联的。一般情况下，我们把测量仪器的误差理解为仪器的示值(测量值)和被测量的真值之间的差值，而准确度则说明仪器示值与被测量的真值相符合的程度。当我们谈到仪器准确度时就会联想到仪器的误差。从误差的观点来看，     

黑潮对环台湾岛海域温跃层影响的数值研究

利用97版POM海洋模式，本文分别对有、无黑潮影响环台湾岛海域三维温度结构进行数值计算，经对比分析得出，由于黑潮的流入，致使整个海域次表层冬季平均水温比无黑潮影响时提高了5－6℃，黑潮对台湾岛东部深水区的水洋跃层有决定性作用，并对台湾海峡及其南部浅水区的季节性温跃层的强度有一定影响。     

交替蛙跳格式在POM的应用

讨论交替蛙跳格式在二维POM的运用。这个交替蛙跳格式是在z坐标下开发的针对线性浅水波方程的一种新的高效无耗散的格式。首先通过一维问题的试验,给出了σ坐标下非线性浅水波的演化特性及其交替蛙跳格式的数值特性,证实该格式的可行性以及优于传统格式的计算效率、守恒性及稳定性。其次,针对该格式二维问题运用讨论了科氏项相应的数值处理,给出了一套完整的数值计算方法,并应用于正压方程和POM外模的数值计算。研究表明,交替蛙跳格式具有两倍于传统蛙跳格式的计算效率,且不再需要Assenlin时间滤波,由此避开了时间滤波带来的数值衰减,具有良好的数值守恒性能。     

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.     

河口海岸三维双σ坐标斜压水流数值模型研究

在海底地形陡变、垂向密度分层明显的水域,三维σ坐标模式中会出现一种"伪"水平斜压梯度力,并会引起"伪"密度流,以至于影响模拟的精度。垂向上引入双σ坐标变换,建立河口海岸水域三维斜压水流数值模型。数值试验结果表明,在海底地形陡变水域,双σ坐标模式可以减小水平斜压梯度力处理引起的误差。     

Low-order pressure gradient schemes in sigma coordinate models: The seamount test revisited

This paper revisits the classic seamount test used in numerous previous studies to evidence the sigma errors of the pressure gradient force (PGF) and their long-term effects on circulation. Two kinds of analysis are developed. We first consider the initial PGF errors. Then, the global level of erroneous kinetic energy is computed along a 180-day simulation. The long-term circulation appears to be better correlated to the initial vorticity errors than to the initial error diagnostics.The original feature of this study is to reconsider the currently admitted idea that Density-Jacobian type PGFs perform better than the primitive sigma formulation discretized in a straightforward way (hereafter Straightforward-Primitive PGF). Errors on the discrete hydrostatic pressure are actually closely related to the way the density field is initialized. If a mass conserving method is preferred to a straightforward initialization, the rectangular integral of the Straightforward-Primitive PGF is likely to be more accurate than the trapezoidal rule usually involved in Density-Jacobian PGFs. Errors on the vorticity field of the Straightforward-Primitive PGF depend on the discretization of the hydrostatic correction term. A modified version of the Straightforward-Primitive PGF is shown to be in better agreement with the concept of bottom torque consistency. The seamount tests show that this so-called Modified-Primitive PGF performs globally better than the current low-order Density-Jacobian PGFs.     

南北向压强梯度力与太平洋赤道潜流的关系

赤道潜流（the Equatorial Undercurrent： EUC）对于大洋环流和全球气候变化有着重要的作用。赤道海区,随着科氏力逐渐趋向于0,地转平衡无法维持,赤道流系无法用地转理论描述。在很多研究中,ENSO、温跃层、海表高度、赤道风应力分布以及其他相关海气要素成为潜流研究的重点要素;压强可以视为温、盐、密、深的复杂关系映射,然而较少有研究将关注重点放在南北向压强梯度力上（the Northward Pressure Gradient： NGT）。在此,本文揭示了南北向压强梯度力的特定函数形式（the Function of Northward Pressure gradient： FNP）与赤道潜流的一个诊断关系。基于原始方程和尺度分析方法,我们得出了该关系的表达形式。结果表明：贝塔效应可能是造成FNP与赤道潜流密切相关的重要影响因子;赤道潜流的垂向结构部分受限于FNP的结构分布;对于赤道潜流来说,南北向压强梯度力相较于东西向压强梯度力更为重要。     

河口海岸三维水流数值模型中几种垂向坐标模式研究述评

回顾了近年来国内外河口、近岸海域三维斜压水流数值模式研究的进展,着重讨论了不同垂向坐标下三维水流模式的发展状况以及存在的问题。地形拟合坐标(σ坐标)模式可以很好地拟合床面地形和自由面,已在物理海洋学中被广泛使用。但在地形变化剧烈,尤其在密度层结效应明显的海域,σ坐标模式中的水平压强梯度力误差会引起伪密度流。寻求高精度的数值模式以及更加有效的拟合坐标变换将是值得努力的方向。     

New modified gradient models for MPS method applied to free-surface flow simulations

In this paper, two modified pressure gradient models based on Taylor series expansion are proposed to enhance the higher order source term MPS (MPS-HS) method. The modified models consist of gradient correction matrices applied to the existing (base) pressure gradient models. To validate the modified pressure gradient models first hydrostatic pressure test is simulated and compared to both the base and modified MPS methods. Using the modified models are shown to reduce unphysical pressure oscillations observed in the base models. Second, an evolution of an elliptical drop in a 2D flow field is examined and shown to verify the models. Third, the proposed models illustrated appropriate stability and consistency properties against analytical solutions when an altered gravitational acceleration was superimposed to the hydrostatic pressure test. In addition, an improved performance is observed when Higher order Laplacian (HL) and Error-Compensating Source (ECS) of the Poisson Pressure Equation (PPE) schemes are coupled with the modified pressure gradient models compared to coupling them with the base gradient models. Finally, the modified MPS methods enhanced performances are validated in a free-surface flow simulation for a dam break problem with impact pressure, and a violent sloshing flow in a rectangular tank when compared to the base MPS methods against an existing experimental data.     

Experimental investigation on the wave-induced pore pressure around shallowly embedded pipelines

A series of regular wave experiments have been done in a large-scale wave flume to investigate the wave-induced pore pressure around the submarine shallowly embedded pipelines.The model pipelines are buried in three kinds of soils,including gravel,sand and silt with different burial depth.The input waves change with height and period.The results show that the amplitudes of wave-induced pore pressure increase as the wave period increase,and decay from the surface to the bottom of seabed.Higher pore pressures are recorded at the pipeline top and the lower pore pressures at the bottom,especially in the sand seabed.The normalized pressure around pipeline decreases as the relative water depth,burial depth or scattering parameters increase.For the silt seabed,the wavelet transform has been successfully used to analyze the signals of wave-induced pore pressure,and the oscillatory and residual pore pressure can be extracted by wavelet analysis.Higher oscillatory pressures are recorded at the bottom and the lower pressures at the top of the pipeline.However,higher residual pressures are recorded at the top and the lower pressures at the bottom of the pipeline.     

Application of a two-way nested model to the seamount problem

A two-way nested model has been constructed and applied to the idealized ocean where a uniform mean flow impinges on the isolated Gaussian-shaped seamount and produces two eddies (cold and warm) in the depths. The performance of the nested model has been evaluated subjectively and objectively. Both subjective and objective analyses confirm the traditional view that the nested model can well capture the performance of isolated eddies. Objective analysis, however, reveals some quantitatively important features of a two-way nested model. One is penetration of improved features into the coarse domain and another is the deterioration of mean flow field inside the nested area, neither of which is clear from subjective analysis. With successful application of two-way nested model to the seamount problem, we expect that such a nested model will also be applicable to other oceanic phenomena, particularly to some coastal problems whose time scale is short and where the topographic effects are dominant.     

北部湾的环流和水团对季节性强迫的响应

In the past 20 a, the gulf-scale circulation in the Beibu Gulf has been commonly accepted to be driven by a wind stress or density gradient. However, using three sensitive experiments based on a three-dimensional baroclinic model that was verified by observations, the formation mechanisms were revealed： the circula- tion in the northern Beibu Gulf was triggered by the monsoon wind throughout a year; whereas the southern gulf circulation was driven by the monsoon wind and South China Sea （SCS） circulation in winter and sum- mer, respectively. The force of heat flux and tidal harmonics had a strong effect on the circulation strength and range, as well as the local circulation structures, but these factors did not influence the major circulation structure in the Beibu Gulf. On the other hand, the Beibu Gulf Cold Water Mass （BGCWM） would disappear without the force of heat flux because the seasonal thermocline layer was generated by the input of heat so that the vertical mixing between the upper hot water and lower cold water was blocked. In addition, the wind-induced cyclonic gyre in the northern gulf was favorable to the existence of the BGCWM. However, the coverage area of the BGCWM was increased slightly without the force of the tidal harmonics. When the model was driven by the monthly averaged surface forcing, the circulation structure was changed to some extent, and the coverage area of the BGCWM almost extended outwards 100%, implying the circulation and water mass in the Beibu Gulf had strong responses to the temporal resolution of the surface forces.     

作业现场回声测深仪的器差订正方法比较

在作业现场使用回声测深仪测量海水深度的实践中,总结出了用于回声测深仪的器差订正方法中比测杆法、比测水陀法、温盐订证法的优缺点和使用范围,指出比测杆法只适用于在海水5 m以浅区域测水深中作比测,比测水陀法不能保证比测的准确性.进而,重点介绍了根据实践经验制作出的比测器的比测过程、步骤和方法,改法通过调整回声测深仪的声速,...