On the Compensation of Systematic Errors in Marine Gravity Measurements

Based on an analysis of the source of errors in marine gravity measurements, an error model, firstly, is constructed mathematically which can characterize the change of systematic errors and with which a new crossover adjustment model is presented in this paper. Then, two methods of compensating the systematic errors are proposed, i.e., the self-calibrating adjustment and the a-posteriori compensation. Some questions involved in solving the adjustment problem, such as the rank deficiency, the choice of error model, the weighting of model parameters and the significance test of compensation efficiency, etc., are discussed in detail. Finally, a practical survey network is used as a case study to test the efficiency and reliability of the two compensation methods.     

测深拼接的组网平差判定方法

从网平差角度研究两相邻图幅的重叠测线间拼接问题,提出3种组网平差模型和图幅间系统误差的判定方法,并通过实例计算比较了组网平差判定法和常用的重叠线直接比对法,计算结果表明,组网平差判定法克服了常用的直接比对法对重叠测线依赖,能有效准确地判定图幅间的系统差异,为测深网拼接提供了更为实用的方法。     

验后平差方法在Geosat/GM卫星测高数据处理中的应用

为了消除多代卫星测高数据之间的不协调性,利用两步处理法对Geosat/GM正常点海面高数据进行自交叉点平差及与T/P卫星测高数据联合平差,发现误差模型的系数计算出现异常,通过分析误差模型及正常点海面高数据的分布特征,找出了出现异常的原因,对计算方法进行改进后,大大提高了计算结果的稳定性和可靠性。     

海洋测量交叉点误差分析(二):系统误差模型的选择

首先对海洋测量交叉点误差分析中系统误差分析进行了回顾,指出系统误差分析是一个模型选择和模型参数估计的双重问题,而传统方法中大多仅涉及了后者而忽略了前者。然后对常用的三种模型选择方法,即假设检验、交叉检核、基于信息论的方法,进行了分析和比较,指出后者更具优越性。最后对以Akaike信息量准则为核心的基于信息论的模型选择方法进行了介绍,给出了Akaike信息量准则的计算公式,比较了同其他模型选择方法的关系,并介绍了基于该准则的模型平均方法和模型选择不确定性评估方法。     

浮体自由衰减运动阻尼识别方法误差分析

讨论了使用Froude法和Faltinsen法识别线性和非线性阻尼系数时的系统误差。通过回顾两种方法的推导过程,论证了方法的内在假设,并量化两种方法的系统误差。为减少识别过程误差,文中提出了直接积分法,并依据数值与试验数据,讨论了3种识别方法识别结果。结果表明,Froude法相比于Faltinsen法能更好地预报线性和非线性阻尼系数。对于低阻尼浮体问题,Froude法和Faltinsen法可以给出相对准确的预测,而对于强阻尼浮体问题,Froude法与Faltinsen法在确定的线性和非线性阻尼系数中会给出大于5%的系统误差,而直接积分法展示了较高的识别精度。     

海洋重磁资料的最小二乘平差处理方法

海洋重磁资料的平差处理是海洋重磁资料处理过程中必不可少的环节之一。从最小二乘算法意义下的平差处理基本理论出发,建立起平羞测线网系统交点误差的方程组,给出了方程组系数矩阵的简单求取方法。理论计算和实际资料处理结果表明,该方法不仅原理简单,计算机实现方便,而且经平差处理后的系统交点误差可以达到最小二乘意义下的极小。最后讨论了实际重磁资料平差处理中任意常数的确定问题。     

海洋重磁测网调差的若干理论研究

为从海洋重磁测网的观测资料中确定并扣除各测线含有的系统误差，本研究对调差方法进行理论研究。     

Determination of space and time sea wave structure from frequency characteristics of the radio signal scattered by the sea

A method of determining sea-wave parameters from frequency characteristics of an RF signal scattered by the sea surface is considered. The method is based on the Doppler frequency shift due to orbital velocity of motion of long sea waves. It is shown that by measuring the frequency shift ofS-band signals scattered by a small (as compared to the sea-wave length) site on the sea surface, one is able to determine both integrated sea-wave parameters (e.g., rms waveheight and mean period) and the space-time structure of energy-carrying sea components. Results of field tests are presented substantiating the efficiency of the method and allowing measurement accuracy to be evaluated. The main systematic errors of the method are discussed.     

海洋环流模式中不同近似假设下的海表高度

Boussinesq近似是现代海洋环流模式中经常采用的假设，但随着海洋模式的不断发展完善以及气候研究应用的需要，有必要估算Boussinesq近似造成的模式误差。分别利用一个非Boussinesq近似的海洋模式与另一个结构相同且采用Boussinesq近似的模式计算海表高度，并同时利用模式预报的温度、盐度资料计算了比容异常高度。分析结果显示，这3种不同定义的海表高度无论空间结构，还是时间演变，都基本类似，尤其在热带海区最接近，差值≤1cm。Boussinesq近似意味着在模式中以体积守恒代替质量守恒，通常的做法是对其进行简单的质量补偿来保持质量守恒。比较说明，以质量补偿方法进行的高度订正对减小Boussinesq近似带来的误差没有本质的意义。     

具有运动补偿高精度海洋气象多参数模拟仪的研制

针对船舶气象仪的综合检查过程中检测周期长、人工排查效率低以及传统的自动气象站传感器信号模拟器的模拟精度低,没有相关运动补偿算法导致此类系统不适应海洋船舶应用环境的问题,对气象要素传感器的高精度信号采样电路、信号输出、软件滤波和运动补偿等方面进行了研究。通过分析传感器和船舶气象仪的原理,设计了各个气象参数的采样电路、信号模拟电路、触摸屏、GPS和电子罗盘采样与模拟电路,并在近海测试过程中进行了运动补偿模型测试,并基于STM32微控制器进行了该仪器的系统检测实验。研究测试结果表明：该系统具有低功耗、高可靠性、高精度的特点,能应用于海上环境,同时具有对船舶实时定位、气象要素实时模拟和采集、运动补偿多项功能。并且本系统精度在运动补偿后,系统测量方差为0.019 3 m/s,精度提高至接近真实值,均符合《海洋调查规范第3部分：海洋气象观测》的标准。     

Alkalinity titration in seawater: How accurately can the data be fitted by an equilibrium model?

Displaying “calculated minus observed” data for precise titrations of seawater with strong acid permits direct evaluation of important parameters and detection of systematic errors.At least two data sets from the GEOSECS (Geochemical Ocean Sections) program fit an equilibrium model (which includes carbonate, borate, sulfate, silicate, fluoride, and phosphate) within the most stringent experimental error, less than 2 μmol kg⁻¹. The effect of various parameters on the fit of calculated to observed values depends strongly on pH. Although standard potential E₀, total alkalinity A_t, total carbonate C_t, and first acidity constant of carbon dioxide pK₁ are nearly independent, and can be determined for each data set, other parameters are strongly correlated. Within such groups, all but one parameter must be determined from data other than the titration curve.Adding an acid-base pair to the theoretical model (e.g. C_x=20 μmol kg⁻¹, pK_x=6.2) produces a deviation approaching 20 μmol kg⁻¹ at constant C_t; however, adjustment of C_t by about −18 μmol kg⁻¹ to produce a good fit leaves only ± 1.5 μmol kg⁻¹ residual deviation from the reference values. Thus, at current standards of precision, an unidentified weak acid cannot be distinguished from carbonate purely on the basis of the titration curve shape.There are few full sets of numerical data published, and most show larger systematic errors (3–12 μmol l⁻¹) than the above; one well-defined source is experiments performed in unsealed vessels. Total carbonate can be explicitly obtained as a function of pH by a rearrangement of the titration curve equation; this can reveal a systematic decrease in C_t in the pH range 5–6, as a result of CO₂ gas loss from the titration vessel. Attempts to compensate for this by adjustment of A_t, C_t, or pK₁ produce deviations which mimic those produced by an additional acid-base pair.Changing from the free H⁺ scale (for which [HSO₄⁻] and [HF] are explicit terms in the alkalinity) to the seawater scale (SWS) (where those terms are part of a constant factor multiplying [H⁺]) requires modification of the titration curve equation as well as adjustment of acidity constants. Even with this change, however, omission of pH-dependent terms in [HSO₄⁻] and [HF] produces small systematic errors at low pH.Shifts in liquid junction potential also introduce small systematic errors, but are significant only at pH <3. High-pH errors due to response of the glass electrode to Na⁺ as well as H⁺ can be adequately compensated to pH 9.5 by a linear selectivity expression.     

海洋重力不规则测线网平差模型对比分析

基于国际共享MW9006航次船载实测资料,针对目前已经被广泛运用的最小二乘和半系统差调整两种平差模型进行讨论,提出了一种适用于不规则复杂测网下重力测线数据的平差方法.规则测线网下,随着半系统差调整平差次数的增加,其结果趋近于最小二乘平差.然而,在实际应用于不规则测线网平差中时,由于存在斜交主测线和联络线的补充测线,最小...     

Rosenbrock methods in biogeochemical modelling – A comparison to Runge–Kutta methods and modified Patankar schemes

Modelling biogeochemical processes in the surface ocean is still a difficult task due to the challenge to identify the most convenient integration scheme for the reaction terms. The scheme is expected to deal with the model characteristics of positivity and conservativity as well as with the different time scales involved, which occur e.g., whenever photochemical reactions take place in the water column.This paper presents a numerical comparison of the Rosenbrock methods, ROS3 and ROS4, often used for solving chemical reactions, to the explicit fourth-order Runge–Kutta method and the unconditionally positive modified Patankar schemes. Following their successful application in air chemistry, we here test the hypothesis that the Rosenbrock methods are an optimal choice for marine biogeochemical modelling in terms of efficiency and accuracy. In this study the schemes are compared in terms of runtime and accuracy and are applied to two test cases of different complexity: a zero-dimensional nutrient–phytoplankton–detritus (NPD)-type model and a one-dimensional nutrient–phytoplankton–zooplankton–detritus (NPZD)-type model. Applying the Rosenbrock methods to the simple NPD model shows their advantage over the other applied methods. They give the most accurate results of all solvers, especially for large step sizes, in less computing time due to their semi-implicitness and adaptive step sizing. On the contrary, for the one-dimensional NPZD model problem this is only the case in comparison to the Runge–Kutta solver, while their performance is worse than that of the second-order modified Patankar scheme. They need longer runtimes than the latter ones in order to achieve similarly accurate results. However, the modified Patankar schemes are not conservative if the system reactions contain more than one source compound. Thus, for more complex marine biogeochemical problems, it is recommended to apply the Rosenbrock methods while for simpler models the use of the second-order modified Patankar method is still the best alternative.     

提高航迹计算精度的方法研究

分析了传统的航迹计算方法存在的系统误差,引入了符号形式的子午线弧长正反解公式,推导出了可以消除该误差进而提高航迹计算精度的精确墨卡托航法。算例分析表明,该方法可以解决航海上不同地球参考椭球下的航迹计算问题,反解精度高达10^-4 m。     

三维斜压台风模式 Ⅱ.预报试验

一种斜压多重移动套网格台网模式在国家海洋环境预报中心已被应用于海洋环境预报。本文第一部分已描述了模式方程组和数值方法。本文继续概述模式网格、变分调整初始化和预报试验结果。最外粗网格域固定,内部细网格域随台风中心轨迹移动。模式中,粗细网格变量采用双向耦合。平衡方程和方程,理想台风场和变分调整方案被用于台风模式初始化。一种简单而有效的资料同化方法,即用第6h台风报和弱约束变分原理调整初始场,被应用于提高预报结果。最后本文给出预报试验结果。预报误差统计显示本模式对台风路径预报具有相当能力,而且可以提供海面风和气压场较好的预报。本模式已经与海浪模式联结,得到满意的波高预报结果。     

Estimation of hydrodynamic coefficients for an AUV using nonlinear observers

Hydrodynamic coefficients strongly affect the dynamic performance of an autonomous underwater vehicle. Although these coefficients are generally obtained experimentally such as through the planar-motion-mechanism (PMM) test, the measured values are not completely reliable because of experimental difficulties and errors involved. Another approach by which these coefficients can be obtained is the observer method, in which a model-based estimation algorithm predicts the coefficients. In this paper, the hydrodynamic coefficients are estimated using two nonlinear observers - a sliding mode observer and an extended Kalman filter. Their performances are evaluated by comparing the estimated coefficients obtained from the two observer methods with the values as determined from the PMM test. By using the estimated coefficients, a sliding mode controller is constructed for the diving and steering maneuver. It is demonstrated that the controller with the estimated values maintains the desired depth and path with sufficient accuracy.     

辽宁海洋生态补偿机制创新与实践路径探讨

辽宁海洋生态补偿研究文献甚少,直面主要课题是机制创新。文章基于公共物品理论、外部性理论、生态价值理论、环境正义理论和可持续发展理论,遵循行为明确性原则、科学性原则、协商性原则、可操作性原则和动态性原则,依照海洋生态系统服务功能、海洋资源资产服务功能、海洋生态系统损害评估、海洋生态系统损失评估报告、海洋生态系统补偿与受偿主体确定、海洋生态系统补偿金额确定、海洋生态系统补偿执行、海洋生态系统补偿监控、海洋生态系统补偿评估与终结等运作程序创建了海洋生态补偿机制。进而,从提升社会公众认知、明确生态补偿制度、完善生态补偿机制、选定价值评估方法和评估生态补偿效益维度,探讨了海洋生态补偿实践路径。     

Comparison of Satellite-Only Gravity Field Models Constructed with All and Parts of the GOCE Gravity Gradient Dataset

The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy.     

Different approaches to model error formulation in 4D-Var: a study with high-resolution advection schemes

All numerical models are imperfect. Weak constraint variational data assimilation ( VDA ), which provides a treatment of the modelling errors, is studied; building on the approach of Vidard et al. (Tellus, 56 A, pp. 177–188, 2004). The evolution of model error ( ME ) is modelled using ordinary differential equations, which involve a scalar parameter. These approaches were tested using different high-resolution advection schemes. The first set of experiments were constructed to see if it is possible to account for (numerical) discretization error within such a framework. In other set of experiments, a systematic source of modelling error was introduced by deliberately specifying an incorrect value for the Coriolis parameter in the model. Results with observational state at half of the model state resolution, are also presented. We also discuss a method of estimating the scalar parameter in the ME through VDA . In all cases, the inclusion of ME provides reduction in forecasting errors. Also, our experiments indicate that different settings of the model (e.g. using different high-resolution advection schemes) would need different ME formulation. Results presented in this paper could be used to formulate sophisticated ME forms to account for systematic errors in higher dimensional models with complex advection schemes.     

半参数回归在测量平差中的应用

针对测量平差中的实际问题,引入半参数回归模型,分析了它在测量平差中应用的可能性,并以实例与经典测量平差方法进行精度分析,说明该方法的有效性。对含有系统误差的测量平差问题进行了试算,为进一步研究半参数回归模型在测量平差中的应用具有一定的意义。