A piecewise curve-fitting technique for vertical oceanographic profiles and its application to density distribution

A unified method of approximation, extrapolation, and objective layering is offered for processing vertical oceanographic profiles. The method is demonstrated using seawater density and consists of adjustable splitting of each individual profile into N vertical layers based on tentative, piecewise linear homogeneous approximation with specified accuracy and a final fitting of an N-layered analytical model to data. A set of 3N coefficients of the model includes one density value at the sea surface; N−1 depths of layer interfaces; and N pairs of coefficients that describe a profile shape within the n-th layer—an asymptotic density value (a key parameter for extrapolation) and a vertical scale of maximum density variability (related to vertical gradient). Several distinctive characteristics of the technique are: (1) It can be used for the analysis of the vertical structure of individual profiles when N is an unknown parameter, and spatial interpolation when N should be equal for all profiles. (2) A justified downward extrapolation of incomplete data is possible with the model, especially if historical deepwater profiles are available. (3) Layer interfaces, as well as other coefficients, are derived with only one fitting to the entire profile. (4) The technique, using its general formulation, can serve as a parent for developing various types of models. The simpler step-like (with hyperbolic or exponential approximation) and more complicated smooth (continuous in gradient space) models were designed and tested against a large number of density profiles from the Sea of Okhotsk and the Gulf of California. Comparison of parametric, z-levels and isopycnal averaging was done for the region off the northeastern coast of Sakhalin.     

Response functions of the temperature and conductivity sensors of CTD profilers

The effect of the boundary layer of the fluid on the response time of the temperature and electric conductivity sensors of a CTD profiler at its motion in a water medium is discussed. The suggested response functions of these sensors depending on the velocity of the slip differ from those accepted before and agree well with the results of known laboratory experiments.     

A method of oceanographic data assimilation based on the theory of optimal control

Fundamental points of the computational procedure for the assimilation of observations by a model for a large-scale ocean circulation are discussed.Translated by Vladimir A. Puchkin.     

发展海洋科技政策的基本原则与实施措施

文章通过对海洋科技政策基本原则的概述,根据一些统计资料的分析,指出了确保海洋科技政策实施的四项基本措施。     

无人机组网技术在海洋观测中的应用研究

为了应对海洋多个观测平台间组网通信的迫切需求,作者从体系架构和通信链路等多个层面对无人机组网通信技术的研究进展进行总结,并关注了军用和搜救方面的特殊应用。最后结合实际项目中多机协同海洋观测的具体场景,分析了现有无人机组网通信技术的成果和不足,指出了未来的发展方向。     

The optimum dimensions for a long-range, autonomous, deep-diving, underwater vehicle for oceanographic research

From the results of a parameter optimization process based on a “minimum feasible volume” criterion, it is shown that the optimum shape for a transatlantic, deep-diving, autonomous submersible is a “low drag” hull shape with a displaced volume of 4.4 m³, a length of 5.97 m and a maximum diameter of 1.33 m. Calculations show that a vehicle of these dimensions, travelling in a minimum drag “cruise” configuration at a depth of 3000 m, say, and at a velocity of 2.5 m/sec could have a maximum range of 7000 km provided the “hotel” power consumption is kept low.     

贝类杂交及杂种优势理论和技术研究进展

中国是个海水养殖大国,也是贝类养殖大国,贝类养殖产量占中国海水养殖总产量的80％左右。目前在中国海水养殖的贝类有20余种,但主要种类如皱纹盘鲍(Haliotis discus hannai)、杂色鲍(Haliotis diversicolor)、栉孔扇贝(Chlamys farreri)、海湾扇贝(Amopecten irradians)、长牡蛎(Crassostrea gigas)、近江     

叶绿素传感器海上应用影响因素研究进展

叶绿素浓度是衡量海洋浮游植物丰度的重要指标,快速准确地测定海水中的叶绿素含量,对于业务化监测和科学研究都具有重要的现实意义。基于活体荧光法的叶绿素传感器操作简便,可长期原位在线监测,能轻易获取大量实测数据,是当前海水叶绿素高精度测量手段的主要发展趋势。由于在海上应用时受到多种环境因素的影响,叶绿素传感器数据与实验室萃取法数值之间存在较大偏差。作者综述了科学界在浊度、光照、温度、盐度等海洋环境因素及藻类生理因素对叶绿素传感器测量的影响规律、影响机理和数据校正方法的研究进展,并对活体荧光法叶绿素传感器海上应用数据质量控制方法的研究思路进行了展望。     

Use of enhanced infrared satellite imagery for sea ice and oceanographic studies

Infrared (i.r.) imagery from the NOAA 2,3, and 4 satellites could be used to measure accurately the absolute temperature of the sea surface and sea water. Comparison with measured temperatures indicate that the satellite observed values are within 2°C of those measured. Contouring temperatures and observing temperature fluctuations within 0·5°C is also possible by enhancing the infrared image. This is done by confining the 16 steps of gray of the image to a desired small temperature scale. The existence of open water areas within the pack ice and the positions of the ice edges could be readily distinguishable by generating special imagery in such a way that the gray scale covers two temperature ranges with a gray tone jump at the freezing point of sea water. In this way ice-water boundary appears as a line of demarcation between two different gray tones. Because the i.r. imagery is available all year round these techniques are readily applicable at all times especially during the winter months when the low sun angles make visible imagery not useful.     

The localization of distributed acoustic sensors

This paper presents a method for the determination of array-element locations that makes no assumptions on the distribution of the sensors along the array or the array shape, and in fact, can be applied to the determination of the locations of sets of arbitrarily distributed sensors and arrays containing loops. The method employed uses multiple far-field sources.     

The complex vibrations and implied drag of a long oceanographic wire in cross-flow

A cylinder in cross-flow experiences periodic forcing related to the shedding of vortices in its wake. Long wires in the ocean vibrate in response to this forcing, but their length and damping is such that boundary conditions do not generally apply to solutions of the equations of motion and their vibratory behavior at one point is of little consequence at remote points. The bulk of previous studies of vibrating wire characteristics have utilized only short wires or cylinders in the laboratory, so have not considered or even permitted this phenomenon.During a typical deployment of the Scripps Deep-Tow survey system to 2800 m a small 2-axis accelerometer package was attached to the tow wire at a depth of 30 m and its output recorded in a diver-operated vehicle about 1 m downstream. Analysis of this data produced sharply peaked spectra with the frequencies of vibration in the direction of flow twice those across the flow. Good correlations were found between mean amplitudes across the flow and the corresponding peak frequencies, and between mean amplitudes across and aligned with the flow. Preference for a specific phase relation between motions in the two planes suggests that vortex shedding occurs progressively and forcing has the form of a complex wave travelling down the wire.To investigate the implications of the preceding, a tow-tank fixture was built which permitted reproduction of amplitude, frequency and phase relations in a cylinder representing a point on the wire. A series of runs were then made to measure drag force directly and obtain an empirical drag law. A constant drag coefficient of 1.8 was found in the Reynolds number range 7000–12000, contrary to other investigations that have ignored vibrations in the flow direction.     

Development of a skill assessment tool for the Korea operational oceanographic system

A standard skill assessment(SA) tool was developed and implemented to evaluate the performance of operational forecast models in the Korea operational oceanographic system.The SA tool provided a robust way to assess model skill in the system by comparing predictions and observations,and involved the computation of multiple skill metrics including correlation and error skills.User-and system-based acceptance criteria of skill metrics were applied to determine whether predictions were acceptable for the system.To achieve this,the tool produced a time series comparison plot,a skill score table,and an advanced summarized diagram to effectively demonstrate the multiple skill scores.Moreover,the SA was conducted to evaluate both atmospheric and hydrodynamic forecast variables.For the atmospheric variables,acceptable error criteria were preferable to acceptable correlation criteria over short timescales,since the mean square error overwhelmed the observation variance.Conversely,for the hydrodynamic variables,acceptable root mean square percentage error(e.g.,p erms) criteria were preferable to acceptable error(e.g.,erms) criteria owing to the spatially variable tidal intensity around the Korean Peninsula.Furthermore,the SA indicated that predetermined acceptance error criteria were appropriate to satisfy a target central frequency(fc) for which errors fell within the specified limits(i.e.,the fc equals 70%).     

Reconstruction of incomplete oceanographic data sets using empirical orthogonal functions: application to the Adriatic Sea surface temperature

A method for the reconstruction of missing data based on an EOF decomposition has been applied to a large data set, a test case of Sea Surface Temperature satellite images of the Adriatic Sea. The EOF decomposition is realised with a Lanczos method, which allows optimising computational time for large matrices. The results show that the reconstruction method leads to accurate reconstructions as well as a low cpu time when dealing with realistic cases. The method has been tested with different amounts of missing data, artificially adding clouds ranging from 40% to 80% of data loss, and then compared to the same data set with no missing data. A comparison with in situ data has also been made. These validation studies show that results are robust, even when the amount of missing data is very high. The reconstruction of the data from the Adriatic Sea shows realistic features and a reliable temperature distribution. In addition, the method is compared to an Optimal Interpolation reconstruction. The results obtained with both methods are very similar. The main difference is the computational time, which is reduced nearly 30 times with the method presented here. Once the reconstruction has been performed, the EOF decomposition is analysed to show the method’s reliability, and a cold event on the Albanian coast is studied. The reconstructed data reflect the effect of wind on the Albanian coast, that led to a cold-water episode in this zone for a 6-day period.     

An autonomous instrument for time series analysis of TCO2 from oceanographic moorings

The design and testing of a robotic analyzer for autonomous TCO₂ measurement from oceanographic moorings is described. The analyzer employs a conductimetric method of TCO₂ measurement wherein CO₂ from an acidified sample diffuses across a semi-permeable membrane into a NaOH solution decreasing the conductivity of the base. The instrument is capable of ～850 analyses over a period of at least six months. It is designed to operate to depths of at least 1000 m. TCO₂ calibration is based on in situ standardization throughout a deployment.We report both laboratory and in situ tests of the analyzer. In the laboratory automated analyses over a period of 38 days at temperatures ranging from 8° to 25 °C yielded a TCO₂ accuracy and precision of ±2.7 μmol/kg. In situ tests were conducted at the WHOI dock with a deployment of 8 weeks at in situ temperatures of 5°–13 °C. The accuracy and precision of TCO₂ analyses over the deployment period, based on in situ calibration, was ±3.6 μmol/kg.Laboratory tests of reagent and standard solution stability are also reported. Standards, based on Certified Reference Material were followed for periods of up to 2 years. In all cases TCO₂ increased. Drift of the standards was the equivalent of ～1 to 3 μmol/kg per 6 months. The conductivity indicator solution was found to be stable for at least 2 months.     

The future of chemical in situ sensors

Many of the sampling methods used in oceanographic sciences today date back decades, if not centuries. Although there has been a marked change in how sampling for chemical oceanography is carried out it still relies on taking samples of seawater from a research vessel in most cases. Assessing processes on small timescales as well as transient events requires higher temporal and spatial resolution of measurements; long time series stations require high duration deployments of instruments. Both requirements can only be adequately satisfied by in situ sensors; for the physical parameters off the shelf instruments are available, in the field of chemical oceanography only a few parameters, such as oxygen, are covered by off the shelf instruments, for most parameters adequate instrumentation only exists in the form of prototypes, if at all. Chemical in situ sensors are needed to gain new insights in how the oceans and the life in it works.     

The joint crossing frequency of stochastic processes and its application to wave theory

The paper introduces the concepts of joint mean crossing frequency and joint mean density of peak values of a stochastic process. These concepts are then used to derive formulate for the extreme values of a narrow-band Gaussian process. It is also shown that the joint crossing frequency can be used to derive the statistical distribution of crest to trough wave heights of a Gaussian process of narrow but finite bandwidth.The methods of extreme value prediction presented incorporates effects of correlation in a rational and simple manner. Specifically, statistical dependence between neighbouring peaks of a narrow-band time series is accounted for. The results given should therefore be of interest to practical design of marine structures.     

Implementation of an expert system for the design of single-point, subsurface oceanographic moorings

The design of single-point, subsurface moorings is carried out a present by a design engineer with the help of some computer programs. These computer programs are used for analyzing the mooring, but the setting-up of the initial mooring configuration and the subsequent modifications on the basis of the results of the analysis are carried out by the design engineer.An expert system for mooring design is developed to eliminate the human expert from the design process and thus to enable a novice to design a mooring by himself. Using the expert system, an optimum least-weight in air design can be developed in much less time than is usually required in conventional procedures. Perhaps the most significant advantage is that the system can serve as a vehicle for effective transfer of present day expertise for future applications.The system is developed and implemented on an IBM PC/AT. It has a user-friendly, interactive, menu-driven input procedure and a sophisticated output facility. The design process is totally automated and the requirement to consult a human expert is easily eliminated. The system has tremendous flexibility and a knowledge engineer can easily adapt it to the specific requirements of a particular user. The concept of machine learning is introduced by recording the failure data and using this information in the later decision-making processes. A CAD package, AUTOCAD, is used to generate the drawings and an interface is developed between the CAD package and the expert system so that the former is transparent to the user.