海浪日最大波高序列的一种标度性质

应用重标度分析方法研究小麦岛海洋观测站１９６１－１９８０年二十年海浪日最大波高序列时发现，该序列并不是相互独立的，而是具有记忆性和持久性，详细的论证表明分式布朗运动模型是描述海浪日最大波高序列的一个较好的模型，同时，应用分式布朗运动模型我们找到了存在于海浪日最大波高序列中的一种标度性质－累积离差（ｔ）的统计自仿射性。     

CTD资料正态性检验方法的探讨

对经预处理并去倾后的ＣＴＤ温一深序列了正态性检验。检验时先用根据序列的自回归模型构成的滤波器去序列元素间之相关性产生白噪声序列，而后用Ｘ＾２－拟合优度检验法对此白噪声序列作正态性检验，得到了较合理的结果。     

多波束相位差序列多项式回归模型阶次的确定

介绍了用方差分析确定正交多项式的步骤，通过仿真数据证明平坦海底的多波束相位差序列多项式模型是二阶的，而实际海底的相位差序列多项式模型是一阶的或是二阶的。应用方差原则来选择相应的阶次。     

全极化X波段雷达掠散射海面回波统计分布特征研究

尽管复Wishart分布已被广泛应用于SAR数据统计分析，然而该分布函数却很少被用来研究雷达海面掠散射回波时间序列的统计特征。本文通过分析IPIX雷达海面掠散射回波数据发现：大尺度海浪遮挡区的雷达回波能量很低，主要是雷达系统噪声，如果将该部分低能量回波数据剔除以后，真实海面的IPIX 雷达回波时间序列数据亦满足圆高斯分布，因此，IPIX 雷达海面回波的时间序列数据也必然满足复Wishart分布。在此，我们基于Wishart分布模型分别对全极化IPIX 雷达不同极化通道数据的海面回波时间序列数据进行了统计研究，并推导给出了不同通道数据协方差矩阵元素实部、虚部及相位差等参数的统计分布函数模型。通过与雷达测量数据比计较可见，推导所得理论统计模型与实际测量数据吻合很好。本文所得结论对进一步深入理解掠散射海面雷达回波的统计特征具有一定理论意义。     

东南太平洋秘鲁鳀资源量预报模型的构建

秘鲁鳀（Engraulis ringens）是栖息于东南太平洋沿岸的一种小型中上层鱼类。有效地对秘鲁鳀资源量进行预报将有助于为我国鱼粉进口企业提供决策支撑。为此，本研究结合秘鲁鳀生物（上一个渔汛季度的资源量、渔获物中的幼鱼比例）和环境（渔场水温和nino1+2区的温度距平）因素及捕捞量为预报因子，利用主成分分析和多元线性回归的方法对17个渔汛季度（2006年至2014年第一渔汛季度）秘鲁鳀的资源量建立预报模型并利用主成分分析的结果对影响秘鲁鳀资源变动的因子进行初步评价。研究表明，随着时间的推移样本量的增加，模型拟合资源量与真实资源量的平均相对误差逐渐下降，拟合资源量序列与真实资源量序列的相关系数逐渐增加。最终模型5（建模数据为2006-2013年第二渔汛季度的数据，验证数据为2014年第一渔汛季度的数据）能够很好地拟合出秘鲁鳀资源量的大小及变动趋势拟合资源量序列与真实资源量序列的相关系数为0.861；拟合资源量序列与真实资源量序列的平均相对误差为12%；预报得到的2014年第一渔汛季度的数据与真实值相比，相对误差为1%。结合主成分分析的结果对影响秘鲁鳀资源变动的因素进行评价结果表明，第一主成分的方差贡献率为46%，其中环境因素占据了最大的载荷；第二主成分的方差贡献率为23%，同样环境因素占据了最大载荷，但是，排名第二和第三的因素分别是上一个渔汛季度的资源量和捕捞量，其载荷相当；第三和第四主成分的方差贡献率分别为9%和7%，其中幼鱼比例占的载荷最大。根据各主成分得分序列与资源量序列的相关系数结果，环境因子对秘鲁鳀资源变动有重要影响。     

海平面变化的小波和自回归模型集成预测试验

针对海面变化预测时间序列模型中趋势组份和周期(准周期)组份的提取和预测问题,基于吴淞站1955～2001年月平均潮位序列,采用小波分析(WA)与自回归(AR)模型相结合的方案,对小波分解的不同尺度分量序列,借助于时间序列模型进行分量预测,再对它们进行叠加建立预测模型,进行了月平均潮位预测试验.以1955～1996年数据为基础建立模型,1997～2001年数据作为验证,结果表明两种方法的结合使用显示了较好的效果,具有较高的精度.     

浒苔水体光谱特征参量时间序列数据拟合研究

开展时间序列浒苔水体光谱特征参量的拟合研究可为寻求最佳拟合方法,从而对进一步开展大尺度的高光谱高空间高时间分辨率遥感动态实时监测具有重要的参考价值。在实验室培养3种不同浓度的浒苔水体,用ASD光谱仪测定并获取浒苔水体的时间序列反射光谱,基于反射光谱定量提取光谱特征参量,构建时间序列数据;应用曲线拟合和时间序列ARMA模型开展浒苔水体光谱特征参量的时间序列拟合研究。结果表明:应用二阶或三阶多项式和ARMA模型可较高精度地拟合浒苔水体的光谱特征参量;但时间序列ARMA模型比多项式拟合模型更能反映浒苔水体光谱特征参量的时间序列数据的分布和变动特性。该研究可为浒苔灾害动态监测业务化运行部门提供浒苔光谱数据,同时也为光谱数据的处理和分析提供一种新的方法。     

基于变形监测管理系统中预测模型的研究

预警报警功能作为建(构)筑物变形监测信息管理系统中的重要功能,其可靠性和精确度显得尤为重要。建(构)筑物变形监测管理系统中所用到的灰色模型与回归分析模型具有良好的可靠性和稳定性,在模型基础上进一步延伸,提高其预测精度,针对多尺度时间序列各尺度单支预测与整合重构的基础上,对变形监测数据进行小波分解成各尺度的子序列,根据各子序列性质配置适合的回声状态网络并进行单支预测,预测子序列经过权值计算重构成预测的序列。实验表明:小波分解理论基础上的回声状态模型预测精度较高。     

基于模糊时间序列的华南台风登陆时最大风速极值预测模型

利用1995—2017年登陆华南地区的台风登陆时最大风速极值数据,构建基于模糊时间序列的台风登陆时最大风速极值预测模型,并将该模型与传统时间序列ARIMA模型作对比。其预测结果表明,模糊时间序列的平均绝对误差、平均相对误差和均方根误差分别为2. 621 m·s-1、0. 066和2. 727 m·s-1,预测的精确度明显高于传统时间序列ARIMA模型,同时也表明将模糊时间序列应用于登陆时最大风速极值的预测能够获得较理想的预测结果。     

基于灰色系统西南大西洋阿根廷滑柔鱼资源丰度预测模型的构建

阿根廷滑柔鱼（Illex argentinus）是西南大西洋鱿钓渔业的主要作业鱼种，对资源丰度进行准确的预测可指导企业合理安排渔业生产。因此，本研究根据2000-2016年我国西南大西洋阿根廷滑柔鱼的生产数据，以单位捕捞努力量的渔获量（Catch per unit effort， CPUE）为阿根廷滑柔鱼资源丰度的指标，利用灰色绝对关联分析和灰色预测建模的方法（GM（0， N）），计算2001-2015年CPUE的时间序列值与产卵期（6-8月）产卵场海表面温度（Sea surface temperature， SST）时间序列值的灰色绝对关联度，选取产卵场海域中灰色绝对关联度大于0.90的海区SST建立资源丰度预测模型，并用2016年实际CPUE进行验证。灰色绝对关联分析表明，6-8月，30°~40°S，45°~60°W海域内存在若干海区的SST与次年对数CPUE时间序列呈现较强的关联度，可作为预报因子。GM（0， N）模型结果表明，以6-8月产卵场SST作为环境因子建立的模型4能较好地拟合出阿根廷滑柔鱼资源丰度变动趋势，与2016年真实值相比，相对误差为7%，该模型可较好地作为阿根廷滑柔鱼资源丰度的预测模型。相反，包含6月和7月SST的模型1效果优于不包含6月SST的模型2或不包含7月SST的模型3，拟合得到的2016年的数据与真实值相比，相对误差分别为128%和289%，这说明6月和7月是西南大西洋阿根廷滑柔鱼的主要产卵月份。     

Wavelet analysis for processing of ocean surface wave records

Wavelet analysis is a relatively new technique and in the recent years enormous interest in application of wavelets has been observed. This modern technique is particularly suitable for non-stationary processes as in contrast to the Fourier transform, (FT), the wavelet transform (WT) allows exceptional localization, both in time and frequency domains. The wavelet transform has been successfully implemented in signal and image processing, ordinary and partial differential equation theory, numerical analysis, communication theory and other fields. On the other hand, the application of the WT to ocean engineering and oceanography is rare. In this paper the WTs capability to give a full time–frequency representation of the wave signals is demonstrated. The processing of the time series of the non-stationary deep water waves, waves breaking at the tropical coral reefs and mechanically generated waves in the wave flume demonstrates the ability of the wavelet transform technique to detect a complex variability of these signals in the time–frequency domain. Various spectral representations resulting from the wavelet transform are discussed and their application for wave signals is shown.     

Weak-mode identification and time-series reconstruction from high-level noisy measured data of offshore structures

The identification of true weak modes buried in high-level, noisy, measured data from offshore structures is a practical but challenging problem because weak modes are typically eliminated as noise and rarely, yield a discrete time series. This study proposes a weak-mode identification and time-series reconstruction method for offshore structures when high-level noise is present. A theoretical development proposed in this study extends the traditional modal analysis to reconstructing the discrete time series of weak modes, thereby removing its previous limitations to only frequencies, damping ratios and mode shapes. Additionally, a second development proposed in this study makes the reconstructed time series not simply a combination of harmonic components from a Fourier transform but rather complex exponentials; the damping of the test structure is thus estimated with a better accuracy. A third theoretical development avoids variations in the results from different original signals by handling multiple signals simultaneously. The proposed approach primarily includes three steps: (1) estimate the poles and corresponding residues of high-level, noisy, measured data by converting high-order difference equations to first-order difference equations; (2) isolate the poles of weak modes by assigning multiple rough-pole windows, and subsequently extract the corresponding residues based on the row number of the isolated pole vector; and (3) identify and reconstruct the time series of the weak modes of interest in the form of complex exponentials. The most primary advantage of the proposed process in engineering applications is that the pole windows can be easily obtained and assigned from the relationship between the frequencies and their poles. Three numerical examples are studied: the first presents the detailed numerical operation of the proposed method, the second extends the proposed method from managing one signal to managing multiple signals, and the third demonstrates the advantage of the approach compared with traditional methods. The numerical results indicate that the original signals can be decomposed into multiple complex exponentials with representative poles and corresponding residues, and that the new signals representing weak modes could be reconstructed by assigning a range of frequencies in terms of their relations with the poles. To study the performance of the proposed method when applied to offshore structures such as offshore platforms and marine risers, the experimental data from the high mode VIV experiments sponsored by the Norwegian Deepwater Programme (NDP) are used firstly. The results show that two dominant frequencies corresponding to the in-line and cross-flow directions can be identified simultaneously even one mode is very weak compared with the other, and the time series of the weak mode could be reconstructed with a rough frequency window. Then sea-test data of two offshore platforms are used: one was collected from the JZ20-2MUQ offshore platform when it was excited by ice, and the other was collected from the WZ11-4D platform when it was excited by waves. The results further demonstrated that a large model order is required to estimate all poles and residues of the original noisy signals, and that the row number corresponding to a weak mode of the isolated pole matrix could be easily determined via finite element analysis or engineering experiences. Therefore, the proposed approach provides not only modal parameters, such as frequencies and damping ratios of true weak modes buried in high-level noise, but also the discrete time series of the weak mode.     

Deterministic non-linear wave prediction using probe data

The accurate prediction of non-linear sea states represents a great challenge, with a number of applications in oceanography, marine engineering, security of people and marine transportation, etc. In this paper, we report on the development of two efficient deterministic prediction models for 2D irregular wave-fields. These models are based on the exploitation of wave elevation time series given by one or more probes and on the use of two different numerical models for the wave-fields simulation. Two effective data assimilation processes are developed to improve the wave-field estimates obtained from the study of one or several probe signals, so that we obtain proper initial conditions for the forecast. The assimilation schemes have been validated on the reconstruction of model-generated observations and accurate predictions of the corresponding synthetic wave-fields evolution have been obtained.     

A new bathyphotometer for bioluminescence measurements on the Armorican continental shelf (northeastern Atlantic)

A new bathyphotometer has been developed by the Oceanographic Laboratory of the French Naval Academy which has performed a series of in situ bioluminescence measurements since 1994. It is used as an additional probe to a Seabird ® CTD. It measures planktonic bioluminescence. It is associated with a SeaTech ® fluorometer. The Armorican shelf has particularly been investigated since July 1994. Results obtained in January and April 1995 off Brittany (France), at the entrance to the Bay of Douarnenez and in the northern Bay of Biscay are presented as examples. A method to separate the bioluminescence background from sharp peaks is presented. The strength of bioluminescence signals was related to seasonal planktonic biomass fluctuations, low in winter, higher in spring.     

The New Form of Time-Dependent Mild Slope Equation for Random Waves

The mild-slope equation derived by Berkhoff (1972), has widely been used in the numerical calculation of refraction and diffraction of regular waves. However, it is well known that the random sea waves has a significant effect in the refraction and diffraction problems. In this paper, a new form of time-dependent mild slope equation for irregular waves was derived with Fade approximation and Kubo's time series concept. The equation was simplified using WKB method, and simple and practical irregular mild slope equation was obtained. Results of numerical calculations are compared with those of laboratory experiments.     

A numerical study on dynamic properties of the gravity cage in combined wave-current flow

Recent work in the area of open-ocean aquaculture-system dynamics has focused either on the response of fish cages in waves or the steady drag response from ocean currents, not on them combined. In reality, however, the forces bearing on these open-ocean structures are a nonlinear, multidirectional combination of both waves and current profiles. In this paper, a numerical model has been developed to simulate the dynamic response of the gravity cage to waves combined with currents. When current flows are combined with regular waves, gravity-cage motion response (including heave, surge, and pitch) and mooring-line forces have been calculated. To examine the validity of simulated results, a series of physical model tests have been carried out. The results of our numerical simulation are all in close agreement with the experimental data.     

Numerical modeling of the influence of cool skin on the heat balance and thermal regime of a water body

The influence that cool skin has on the energy exchange between the atmosphere and the ocean is investigated in this work. For this purpose, a series of numerical experiments with the use of the one-dimensional LAKE model of a water body were performed. Three types of cold-skin parameterization were used in this model. The data of in situ measurements in the coastal zone of the Black Sea, in the Arctic Ocean, and over Lake Sparkling served as the boundary and initial conditions. It has been established from the results of experiments that the LAKE model with the incorporated parameterization of the cool skin successfully reproduces cold-skin characteristics, namely, the difference between the temperature of the cool skin surface and the water temperature below the skin. The results of numerical experiments are within the variability of the results of in situ measurements. It has been shown that the presence of a cool skin reduces the heat losses of a body of water. The numerical experiments showed that the presence of a cool skin can change the thermal regime of a water body and its stratification by changing the heat balance at the surface. This result can be important for the modeling of many processes inside a body of water and at its surface, for example, gas and heat exchange.     

Elastic instability of thin cylindrical shells: Numerical and experimental investigation

Thin walled cylinders under external pressure may be affected by instability phenomena particularly dangerous when taking place in the elastic domain. Geometric imperfections caused by fabrication processes heavily influence the critical pressure. In order to investigate the relationship between the collapse mechanism and the various types of imperfections affecting this kind of structures a series of experimental tests on scale models has been carried out. The dimensional parameters of the specimens have been selected in order to keep the instability phenomenon in the elastic range. At the same time numerical calculations simulating the experimental tests have been performed by finite element method. The geometrical defects measured on the specimens were introduced in the correspondent numerical models. A good agreement was found in the comparison between experimental and numerical results.     

On the evaluation of time-domain Green function

An analytical method has been developed to evaluate the wave part of the time-domain Green function and its derivatives. Based on Taylor series expansion, the Green function is obtained by solving a fourth-order ordinary differential equation. The method accelerates the convergence of the summation of an infinite series in the numerical computation. The accuracy of this method was demonstrated by its comparison with other method and its application to solve the radiation problem of a floating hemisphere using a panel-free method. The computed hydrodynamic coefficients agree well with the analytical solutions.