基于 MODWT航行数据滤波方法变换的海洋重力观测

厄特弗斯效应是动态海洋重力测量的主要误差来源,厄特弗斯改正精度与航速和航向角精度密切相关。本文从最大重叠离散小波变换系数的分布特性入手,利用改进的定量化 Lipschitz 条件来确定观测曲线的正则性,提出了一种海洋重力观测中含噪航行数据的滤波方法,该方法在抑制噪声干扰的同时能够很好地保留测量信号的局部特征。本文提供了两组海洋重力测量中航速和航向角数据的处理结果,充分验证了本文方法的可靠性与有效性。     

Prediction and observation of a model gravity platform on Drammen clay

The results of five centrifuge tests of a stiff circular model platform on overconsolidated undisturbed Drammen clay are reported from Manchester University together with predictions computed at the Norwegian Geotechnical Institute. Towards failure the models developed high shear strain and softening local to the base, accompanied by a permanent settlement or shakedown. A total stress transfer from edge to centre caused a rapid increase of excess pore pressure under the centre, having a high vertical gradient. These features, and failure values which decreased with increase in eccentricity of loading, conformed with previous observations on reconstituted clays. Comparison of observations with predictions highlights the sensitivity of the analytical method to the fineness of the finite element mesh just below the base. The predictions also indicated a sensitivity of the failure load to the degree of overconsolidation associated with a given undrained shear strength. The elastic type analysis did not predict the degree of shakedown which was associated with plastic displacement of clay from just under the base.     

Inverse estimation of drifting-object outflows using actual observation data

The present study attempts to establish a scientifically reliable method capable of computing the drifting-object sources and their outflows. First, the temporal variability of the drifting-object amount is investigated every two months on a beach west of Japan, where various source regions are anticipated because of spatiotemporally variable northeastward ocean currents over the East China Sea. Next, in order to specify drifting-object sources, two-way particle tracking model (PTM) experiments are carried out using simulated ocean currents and leeway drift estimated from QuikSCAT/Seawinds wind data. Finally, an inverse method with a Lagrange multiplier is applied to estimate drifting-object outflows at each source on the basis of the two-way PTM results and beach surveys. Accuracy of object-source identification using the two-way PTM is validated by comparing disposable-lighter sources suggested by phone numbers printed on the lighter surface with those computed by the model. In order to examine the reliability of the inverse estimation, the number of plastic-bottle caps found in actual beach surveys is compared with that computed using a forward in-time PTM during the same period of actual beach surveys, over which the outflows obtained using the inverse method are given at each source in the model.     

晃动平台上海-气通量观测误差矫正模型

为了更准确地计算由平台晃动所带来的通量观测误差, 从平台晃动与风速仪测点位置变化角度以分层平均消除垂向均值差异的办法建立了新的涡相关通量误差矫正模型。结果是： 在中高海况下由平台晃动引起的通量观测误差是显著的。有鉴于此, 将晃动平台视为固定平台来处理的常用通量计算公式在中高海况下可能会给出严重失真的结果, 建议采用新公...     

Geometric distortions in side-scan sonar images: a procedure fortheir estimation and correction

A procedure is introduced for the estimation and correction of geometric distortions frequently observed in side-scan sonar images as a result of motion instabilities of the sonar towfish. This procedure estimates geometric distortions from the image itself, without requiring navigational or altitude measurements. Estimates of the local degree of geometric distortion are obtained by cross-correlating segments of adjacent lines of the image. A mathematical model for the distortions is derived from the geometry of the problem and is applied to these estimates to reconstruct the sampling pattern on the seabed, under the assumption of a planar bottom. The estimated sampling pattern is then used for resampling the image to correct the geometric distortions. The model parameters may also be used for calculating approximate estimates of the attitude parameters of the towfish. A simulation is employed to evaluate the effectiveness of this technique and examples of its application to high-resolution side-scan sonar images are provided     

On the estimation of surface gravity waves from subsurface pressure records for estuarine basins

According to small-amplitude theory, the surface gravity-wave spectrum can be estimated from a subsurface pressure-fluctuation spectrum by applying a factor (K) that compensates for the attenuation of surface-wave amplitude as the depth below the water surface and the wave frequency increase.There are a number of factors, however, that cause K to be inaccurate over a large portion of the spectrum's frequency range. Numerous attempts have been made to derive an empirical correction factor (n) that could be applied to K to provide a better estimate of the surface-wave spectrum. This paper evaluates some of these empirical factors, specifically for use in an estuarine environment, and recommends Graces' (1978) equation for n as a function of the non-dimensional frequency parameter kh (where $\text{k =}\text{2π}\text{L}$ is the local wavenumber, h the local depth and L the wavelength).The paper also evaluates the maximum limit (K_max) on the magnitude of K suggested by Esteva & Harris (1970), where relative depth $\text{d}\text{h}$ (d is the pressure transducer height above the bottom) and k_oh (a parameter directly related for large values of kh to wave frequency by the dispersion relation) are the independent variables. The choice of K_max may be made unimportant if d is selected beforehand using an equation (Knowles, 1981a) for the minimum $\text{d}\text{h}$ limit affected by the choice of K_max.     

基于不同水位观测时长下的深度基准面精度分析

深度基准面是海图水深的起算面,其精度直接影响着真实水深的精度.《海道测量规范》中对深度基准的求解方法进行了规定,但是未对其求解精度进行要求.因此本文采用我国10个验潮站19a间水位观测数据,分析了各站点不同水位观测时长求解的平均海面精度和深度基准精度,实验结果表明,对于港航区域重要长期验潮站,海图深度基准的设定应该采用...     

沿海验潮站GNSS观测网BDS与GPS基线处理精度分析

为了评估北斗卫星导航系统（BDS）用于验潮站沉降监测的可靠性和精度,该文利用北海区沿海8个验潮站2022年全年的GPS和BDS观测数据,从基线解标准均方根误差、基线重复性和GPS与BDS基线互差等方面对GPS和BDS解算结果进行对比分析。结果表明,BDS基线解的NRMS值在0.17～0.25之间,GPS基线解的NRMS值在0.18～0.23之间,二者基线解的NRMS值基本相当;GPS基线解的长度和各分量基线重复率平均值要小于BDS,从GNSS网固定误差和比例误差看,GPS和BDS的基线长度重复性精度达到10-9～10-8量级,基线东西和南北分量重复性达到10-9量级,基线垂直分量重复性精度达到10-7～10-8量级。在GPS和BDS基线结果互差方面,GPS解算得到的基线长度均要大于BDS,二者平均差值为10.7 mm;东西分量差值最小,其次是南北分量,垂直分量差异最大,南北分量、东西分量和垂直分量差值平均值分别为-8.5 mm、-3.7 mm和10.6 mm。南北分量、东西分量、垂直分量和基线长度差值平均值最大值分别为23.6 mm、20.9 mm、30.4 mm和22.1 mm。总体...     

自研高精度pH传感器的标定、校正方法及其在海水原位观测中的应用

电化学方法是测量海水pH值的主要方法之一。针对自主研发的基于铱金属及其氧化物电极的pH传感器,建立了海水环境下仪器标定和数据校正的方法,并在近岸和大洋环境中进行了原位测试的应用。仪器标定包括：(1)依照海水pH分析的标度要求选取适当的标定缓冲试剂;(2)以标准海水替代常用的2-氨基吡啶(AMP)溶液制备标定缓冲体系。数据校正主要包括温度背景校正及误差校正。海区原位测试应用以及与其他同类仪器对比表明,标定体系差异带来的误差可达1.00 pH单位,数据校正可提升测试精度0.10～3.00 pH单位不等。仪器的标定与数据校正方法能有效提高该自研pH传感器的测量精度。     

A VGGNet-based correction for satellite altimetry-derived gravity anomalies to improve the accuracy of bathymetry to depths of 6 500 m

Understanding the topographic patterns of the seafloor is a very important part of understanding our planet.Although the science involved in bathymetric surveying has advanced much over the decades, less than 20% of the seafloor has been precisely modeled to date, and there is an urgent need to improve the accuracy and reduce the uncertainty of underwater survey data. In this study, we introduce a pretrained visual geometry group network(VGGNet) method based on deep learning. To apply this metho...     

全球垂向位移负荷潮模式在渤海、黄海、东海及周边区域的准确度评估

本研究利用渤海、黄海、东海及周边区域21个GPS站的调和常数资料,对5个全球垂向位移负荷潮模式(FES2014、EOT11a、GOT4.10c、GOT4.8和NAO.99b)在渤海、黄海、东海及周边区域的准确度进行了评估。结果表明,在渤海、黄海、东海及周边区域,对于M₂分潮,FES2014和EOT11a模式结果准确度相对较高;对于S₂分潮,NAO.99b和EOT11a模式结果准确度相对较高;对于K₁分潮,EOT11a和FES2014模式结果准确度相对较高;对于O₁分潮,EOT11a和GOT4.8模式结果准确度相对较高;对于N₂分潮,EOT11a和FES2014模式结果准确度相对较高;对于K₂分潮,NAO.99b和FES2014模式结果准确度相对较高;对于P₁分潮,EOT11a和GOT4.8模式结果准确度相对较高;对于Q₁分潮,FES2014和EOT11a模式结果准确度相对较高。除此之外,本文还简单分析了渤海、黄海...     

Cyclostrophic balance in surface gravity waves

The cyclostrophic balance (pressure forcevs. force centrifugal force) is shown to be satisfied for all fluid particles in surface gravity waves with sinusoidal form and circular particle orbits. Consequences of the cyclostrophic balance are 1) that the normal dispersion relation for deep water hold and 2) that the orbital radius decrease with increasing depth at the usual exponential rate, from which it follows that the wave pressure and particle speed also decrease with depth exponentially. In addition, the cyclostrophic and hydrostatic balances together predict wave breaking at the crests for amplitudes exceeding one divided by the wave number. In contrast to the traditional perturbation method, based on irrotational flow, the cyclostrophic method does not demand that the amplitude be much less than a wave length and does not require an infinite wave train.     

Identification of mantle and lithospheric components of the gravity field by isostatic gravity anomalies

All anomalous masses of the Earth are reflected in the free air gravity anomalies and the geoidal undulations. The low viscosity of the asthenosphere significantly reduces the possibility of existence of density inhomogeneities in the layer. This fact provides some physical basis for the separation of the gravity field anomalies. It has been shown by power spectrum analysis of the free air anomalies and gravity field of isostatically compensated model of the lithosphere for the North Atlantic and adjacent areas of America, Europe and Mediterranean, that the attraction of isostatically compensated model is significant for any wave length of the field. It causes significant error in the interpretation if long wavelength constituents of the free air gravity anomalies are considered as a field of deep anomalous masses. The isostatic anomalies und isostatic geoid are free from the influences of isostatically compensated lithosphere. The characteristic feature of the isostatic anomalies power spectrum is a pronounced minimum at the wavelength of about 1000 km. The relative homogeneity of the asthenosphere may explain this minimum. It means that principal density inhomogeneities of the Earth's interior are separated by the asthenospheric layer. Such a minimum has not been observed at the power spectrum of free air anomalies being masked by corresponding wavelength of the field of isostatically compensated lithosphere. Isostatic anomalies that reflect the differences between the real structure of the lithosphere and its isostatically compensated model have wavelengths less than 1000 km. Isostatic anomalies with the wavelength more than 1000 km reflect the attraction of density inhomogeneities situated under the level of isostatic compensation. The basic features of power spectrum of isostatic anomalies are the same for oceanic and continental areas. The method based on Kolmogorov-Wiener filtration which consideres statistical characteristics of the field has been developed to divide the isostatic gravity anomalies into lithosphere and mantle components. For the North Atlantic and adjacent areas the field of mantle inhomogeneities has been determined.     

联合重力异常和重力垂直梯度异常数据反演皇帝山海域海底地形

海底地形对开展海洋科学调查和研究十分重要。以多波束为主的回声测深技术测量成本高且效率低,几十年来仅实现了全球约20%的海床测绘。对于空白区（特别是深海区域）,可以借助重力异常和重力垂直梯度异常进行回归分析反演得到,但该方法得到的比例因子鲁棒性不强。为了解决这一问题,同时考虑到两种重力数据在表征海底地形长短波长的不同优势,本文结合滑动窗口赋权和稳健回归分析来反演海底地形。在太平洋皇帝山海域（35°～45°N,165°～175°E）的实验结果表明：在船测检核点处,本文构建模型的标准差为61.02 m,相比于单一重力数据反演模型,精度分别提高了14.92%（重力异常）和2.08%（重力垂直梯度异常）,能较好地反映皇帝海山链的地形走势。     

Particle trajectories of nonlinear gravity waves in deep water

The paper presents a numerical method for calculating the particle trajectories of nonlinear gravity waves in deep water. Particle trajectories, mass-transport velocity and Lagrangian wave period can be accurately determined by the proposed method. The high success rate of the proposed method is examined by comparing the present results with those of (a) Longuet-Higgins, M.S., 1986, 1987. Eulerian and Lagrangian aspects of surface waves. Journal of Fluid Mechanics 173, 683-707 and (b) Lagrangian moments and mass transport in Stokes waves. Journal of Fluid Mechanics 179, 547-555. It is shown that the dimensionless mass-transport velocity can exceed 10% for large waves, and the Lagrangian wave period is much larger than the Eulerian wave period for large waves.     

On the form of crests in limiting gravity waves

Properties of surface singularities and the form of wave crests of limiting gravity waves in steady-state flows of an ideal liquid are considered by analyzing the kinematic boundary condition. It is shown that, for rotational waves, the angle at the crest can have any value from 0° to 180°, while it has the only value 90° in the case of irrotational waves. Two inferences are made from Bernoulli’s integral and the properties of singularities: (i) the Stokes wave is a rotational wave and (ii) no angular points can appear on the profiles of capillary-gravity and capillary waves.     

利用坐底观测估算济州岛西南海域再悬浮临界应力

底边界层中沉积物的再悬浮和沉降是控制陆架海悬浮沉积物的输运的关键过程。沉积物输运过程的数值^*模拟也依赖于沉积物侵蚀和沉降的关键参数的研究。本文根据济州岛西南泥质区的坐底观测估算了此处临界应力。通过底边界层声学仪器ADV和PC-ADP的流速和悬浮物浓度同步观测,基于湍生成与耗散平衡假设,使用惯性耗散法计算沉降速度。这种方法得到的沉降速度ws平均值为0.91 mm s^-1,标准差为0.20 mm s^-1,此结果远大于Soulbsy（1997）和LISST-ST现场观测粒径分析仪等经验方法的结果。这主要是由于两种方法的本质不同,惯性耗散法形象的刻画了底边界层的水动力,并且更加合理的现场估计沉降速度w_s,然而Soulsby的方法通常适用于静水环境。我们提出了一种估计临界应力的新方法,根据悬浮颗粒物浓度时空变化的统计分析（深度平均的悬浮颗粒物浓度对时间求导数）和对应的底应力估算侵蚀临界应力τ_ce和沉降临界应力τ_cd。侵蚀临界应力τ_ce和沉降临界应力τ_ce的变化范围为0.11-0.25 Pa,对应的中值分别为0.20 Pa和0.16 Pa,这也证实了侵蚀临界应力略大于沉降临界应力。除此之外,我们还使用了另一种方法估算临界应力,通过沉降速度间接估算的临界应力范围为0.06-0.17 Pa。