Enhanced estimation of sonobuoy trajectories by velocity reconstruction with near-surface drifters

An investigation to improve trajectory prediction using Lagrangian data is presented. The velocity field of a data assimilating model, EAS-16, is corrected using drifter observations taken during an experiment off Taiwan. The results are tested using another independent Lagrangian data set provided by sonobuoys launched in the same area. The latter have instrument chains that extend well into the water column. Consequently the corrected model velocities were projected into the water column in order to calculate sonobuoy trajectories. The drifter and sonobuoy trajectories both show two distinct regimes in the considered area of approximately 1/2° square. One regime is dominated by shelf dynamics, the other by meandering of the Kuroshio, with a sharp boundary dividing the two. These two regimes are not reproduced by the trajectories of the EAS-16 model. When the drifter data are blended with the model velocities, synthetic sonobuoy trajectories track the observed ones much better, and the two regimes are clearly depicted. Two different methods for the velocity reconstruction are tested. One is based on a variational approach and the other on a normal mode decomposition. Both methods show qualitatively similar improvements in the prediction of sonobuoys trajectories, with a quantitative improvement in the total rms error of approximately 50% and 25%, respectively.     

定向井三向主应力模型及影响因素分析

定向井三向主应力受并眼轨迹、水平地应力方向等因素影响,求解困难,而目前多数井周主应力模型仅针对井壁位置,远离井壁多不适用.此文通过坐标转化方法,建立了定向井三向主应力的求解模型,并且对影响主应力大小的因素进行了研究,研究成果对于定向井井壁稳定、水力压裂等研究有一定的借鉴意义.     

Steady Lateral Growth of Three-Dimensional Particle Laden Density Currents

In this paper the steady lateral growth of three-dimensional turbulent inclined turbidity current is investigated. To simulate the current, an experimental setup is developed to analyze the turbidity current for different regimes in the particle laden density currents environment. The Buckingham's π theorem together with a dimensional analysis is implemented to derive the appropriate non-dimensional variables. The experimental results were normalized and plotted in the form of non-dimensional graphs from which a theoretical model is developed and analyzed. Based on the results obtained for the steady lateral growth, three different regimes, namely, inertia-viscous one as the first regime, buoyancy-viscous and gravity-viscous as the second and third regimes are distinguished within the current.In these regimes, the force balance is between the driving and resisting forces. Namely, in the first regime, the force balance is between the inertia and viscous forces, in the second regime, the buoyancy and viscous forces, and in the third regime, gravity and viscous forces are balanced. The experimental results indicate that the lateral growth rate in the first regime is smaller than that in the second and third regimes due to the magnitude and type of the forces involved in those regimes. According to the graphical results, the three different lateral growth rates appear when the normalized current length is smaller than about 3, between about 3 and 10, and larger than about 10. In those regions,the slopes of the data are different with respect to one another.     

Underwater Vehicle Navigation Using Diffusion-Based Trajectory Observers

This paper addresses the issue of estimating underwater vehicle trajectories using gyro-Doppler (body-fixed velocities) and acoustic positioning signals (earth-fixed positions). The approach consists of diffusion-based observers processing a whole trajectory segment at a time, allowing the consideration of important practical problems such as different information update rates, outages, and outliers in a very simple framework. Results of contraction theory are used to prove that the observers are convergent, i.e., stable in the incremental sense. Simulation and experimental results are presented to illustrate the potential of application of the method.     

不同模态下气候变化对智利竹筴鱼补充量的影响

智利竹筴鱼(Trachurus murphyi)是东南太平洋重要的经济鱼类之一,其资源量受补充量影响明显,了解补充量状况对智利竹筴鱼资源可持续利用和科学管理具有重要意义。本文基于模态分析将1971?2017年间智利竹筴鱼补充量划分不同模态,运用贝叶斯模型平均法,分析海表面温度、海表面盐度、海表面高度、厄尔尼诺和太平洋年代际振荡5个环境因子在不同模态中对补充量的解释能力,并探讨模态变动对补充量预测的影响。结果表明,第1模态(1971?1980年)更多的受捕捞因素的干扰;第2模态(1981?1990年)厄尔尼诺对补充量变动的解释概率最高;第3模态(1991?2001年)解释概率最高的环境因子为太平洋年代际振荡;第4模态(2002?2015年)厄尔尼诺为解释概率最高的环境因子。对比不考虑模态变动的分析结果,两者存在明显差异,基于不同模态的分析结果对智利竹筴鱼补充量变动的解释更为合理。研究认为,智利竹筴鱼补充量变动受到多个环境因子的影响,在不同模态时期起主导作用的环境因子也不同,推测年代际太平洋年代际振荡冷暖期交替与厄尔尼诺现象可能是诱发智利竹筴鱼补充量发生模态转变的重要因素。建议在未来智利竹筴鱼资源评估与管理中,应该考虑不同的模态变化及其影响因子。     

Projecting uncertainty onto marine megafauna trajectories

In this study, a method is proposed for estimating the uncertainty of a Lagrangian pathway calculated from an undersampled ocean surface velocity field. The primary motivation and application for this method is the differentiation between active and passive movements for sea turtles whose trajectories are observed with satellite telemetry. Synthetic trajectories are launched within a reconstructed surface velocity field and integrated forward in time to produce likely trajectories of an actual turtle or drifter. Uncertainties in both the initial conditions at launch and the velocity field along the trajectory are used to yield an envelope of possible synthetic trajectories for each actual trajectory. The juxtaposition of the actual trajectory with the resulting cloud of synthetic trajectories provides a means to distinguish between active and passive movements of the turtle. The uncertainty estimates provided by this model may lead to improvements in our understanding of where and when turtles are engaged in specific behaviors (i.e. migration vs. foraging)—for which potential management efforts may vary accordingly.     

海上无动力船舶漂移轨迹模型及其在“桑吉”油轮漂移模拟中的应用

无动力或破损的船舶在海上自由漂移对海上的各项生产活动是一个巨大的危险。通过对海上漂浮的船舶进行受力分析,考虑船舶的外形特征及漂浮状态,建立了海上船舶漂移轨迹模型,对船舶海面以上与以下侧向投影面积之比(面积比)、风拖曳系数、流拖曳系数等参数均进行了敏感性分析,并针对2018年1月6日爆燃的"桑吉"油轮漂移轨迹开展了模拟应用。结果表明该模型针对不同类型海上船舶的漂移轨迹有一定合理的模拟能力,船舶面积比是准确模拟漂移轨迹的一个重要参数,同时,该模型对风拖曳系数、流拖曳系数较为敏感。针对"桑吉"油轮的模拟,科氏力的作用不可忽视,考虑科氏力作用后漂移轨迹的模拟效果得到了很好的改善。     

Technical issues in modeling surface-drifter behavior on the East China Sea shelf

To investigate technical issues associated with the particle-tracking numerical models frequently used to reproduce the behavior of objects drifting in the actual ocean, the trajectories of satellite-tracked drifters released in 2003, 2004, and 2007 were reproduced using a numerical model. In particular, the wind stress driving the surface currents which carried the drifters has been computed using satellite-observed QuikSCAT/Seawinds data provided twice daily in conjunction with in-situ Ieodo-station wind data. Although it is difficult to reproduce the trajectory of a single drifter using numerical models because of the uncertainty induced by random-walk processes, the similarity between the modeled particle and observed buoy trajectories is statistically significant, except for the experiment in 2007. In general, the satellite-derived wind field modified using in situ data is likely to be able to reproduce observed drifter motion. However, it is found that the model is unable to reproduce drifter trajectories in windy 2007. The numerical modeling result demonstrates that wind-induced leeway drift prevails in drifter motion in 2007, in spite of the wind-resistant drogue attached to the drifters, and that this drift shows non-negligible spatiotemporal variability, suggesting that leeway drift is not simply proportional to wind speeds, as in previous studies have maintained.     

VIV trajectories of an elastically mounted sphere

In this paper, vortex-induced vibrations (VIV) of an elastically mounted sphere with two linear degrees of freedom have been experimentally studied. The dynamic response analysis shows that, for the range of reduced velocity from 2 to 14 here investigated, the sphere exhibits similar amplitudes and frequencies compared to the tethered sphere, and Modes I and II are detected. A new application of the phase average approach allowed extrapolating the periodic trajectory pattern from the experimental trajectories. In particular, more than one dominant harmonic component is observed in the streamwise oscillation, so the sphere trajectories are significantly different from the traditional figure-of-eight shape. The main difference is that these trajectories are not self-intersecting. Based on the experimental observations, an analytical model of the trajectory is built and discussed.     

Dispersion of surface drifters and model-simulated trajectories

From a data set encompassing the years 1990–2008 pairs of surface drifters with maximum initial separations of 5, 10 and 25 km have been identified. Model trajectories have been calculated using the same initial positions and times as the selected pairs of surface drifters. The model trajectories are based on the TRACMASS trajectory code and driven by the ocean general circulation model NEMO. The trajectories are calculated off-line, i.e. with the stored velocity fields from the circulation model. The sensitivity of the trajectory simulations to the frequency of the stored velocity fields was tested for periods of 3 and 6 h as well as 5 days. The relative dispersion of the surface-drifter and model trajectories has been compared, where the latter was found to be too low compared to the relative dispersion of the drifters.Two low-order trajectory sub-grid parameterisations were tested and successfully tuned so that the total amplitude of the relative dispersion of the model trajectories is similar to that associated with the drifter trajectories. These parameterisations are, however, too simple for a correct simulation of Lagrangian properties such as the correlation time scales and the variance of the eddy kinetic energy.The importance of model-grid resolution is quantified by comparing the relative dispersion from an eddy-permitting and a coarse-resolution model, respectively. The dispersion rate is halved with the coarse grid. The consequences of the two-dimensionality of the trajectories is evaluated by comparing the results obtained with the 2D and the Lagrangian 3D trajectories. This shows that the relative dispersion is 15% stronger when the trajectories are freely advected with the 3D velocity field.     

Stress and pore pressure histories in complex tectonic settings predicted with coupled geomechanical-fluid flow models

Most of the methods currently used for pore pressure prediction in sedimentary basins assume one-dimensional compaction based on relationships between vertical effective stress and porosity. These methods may be inaccurate in complex tectonic regimes where stress tensors are variable. Modelling approaches for compaction adopted within the geotechnical field account for both the full three-dimensional stress tensor and the stress history. In this paper a coupled geomechanical-fluid flow model is used, along with an advanced version of the Cam-Clay constitutive model, to investigate stress, pore pressure and porosity in a Gulf of Mexico style mini-basin bounded by salt subjected to lateral deformation. The modelled structure consists of two depocentres separated by a salt diapir. 20% of horizontal shortening synchronous to basin sedimentation is imposed. An additional model accounting solely for the overpressure generated due to 1D disequilibrium compaction is also defined. The predicted deformation regime in the two depocentres of the mini-basin is one of tectonic lateral compression, in which the horizontal effective stress is higher than the vertical effective stress. In contrast, sediments above the central salt diapir show lateral extension and tectonic vertical compaction due to the rise of the diapir. Compared to the 1D model, the horizontal shortening in the mini-basin increases the predicted present-day overpressure by 50%, from 20 MPa to 30 MPa. The porosities predicted by the mini-basin models are used to perform 1D, porosity-based pore pressure predictions. The 1D method underestimated overpressure by up to 6 MPa at 3400 m depth (26% of the total overpressure) in the well located at the basin depocentre and up to 3 MPa at 1900 m depth (34% of the total overpressure) in the well located above the salt diapir. The results show how 2D/3D methods are required to accurately predict overpressure in regions in which tectonic stresses are important.     

基于时空约束和三角形迭代划分的渔船AIS与ARPA轨迹匹配

针对现有的轨迹相似度匹配算法用于渔船AIS (Automatic Identification System)与ARPA (Automatic Radar Plotting Aid)轨迹匹配时存在复杂度高、效率低等问题,本文提出基于时空约束和三角形迭代划分的渔船AIS与ARPA轨迹匹配算法TSC-TIP (Temporal and Spatial Constraint-Triangle Iterative Partitioning)。首先采用时空约束法筛选出ARPA目标时空约束范围内的AIS数据;其次采用三角形相似算法选择与AIS数据具有相似特征点的APRA轨迹数据;最后设计了子轨迹迭代划分法将每条轨迹划分为两条子轨迹并采用三角形相似法对子轨迹进行迭代筛选。为验证算法的性能,用渔船的真实AIS轨迹数据和ARPA轨迹数据进行了试验,结果表明：与基于经典距离的相似性度量方法相比,提出的TSC-TIP算法在不影响匹配准确率的前提下,匹配时间减少了95%。研究表明：TSC-TIP算法能有效匹配渔船AIS与ARPA轨迹数据,为面向AIS与ARPA的渔船轨迹数据融合研究提供了新思路。     

Fracture modes in the Silurian Qusaiba Shale Play,Northern Saudi Arabia and their geomechanical implications

Fracture and in-situ stress studies were conducted for unconventional prospect evaluation in the Silurian Qusaiba Shale, northern Saudi Arabia. Borehole image logs, oriented cores, seismic, and drilling observations were used in the studies. The fractures include natural fractures and induced fractures. The induced fractures were studied to assess the stress regime in terms of directions and magnitudes. The present day maximum horizontal in-situ stress trend varies from NNW-SSE to NNE-SSW, and shows a regional pattern dominated by Arabian plate tectonics. The relative magnitudes of the current day stresses are characteristic of an extensional to strike-slip regime. Natural fractures of microscopic (microfractures) to macroscopic (macrofractures) scales include extension fractures (joints/veins), and faults manifested as shear and hybrid (extensional-shear and compressional-shear) fractures. Joints clustering into zones are rare, unless when associated with fault zones. Over half of the faults (56%) show clustering into fault zones with their widths (thickness) varying by up to 5 orders of magnitude, and lengths and displacements varying by up to 4 orders of magnitudes respectively. The study identified five distinctive, regional, fracture sets: one gently dipping (bedding-parallel or at low angle to bedding) and up to four moderately to steeply dipping fracture sets: an easterly striking set is the oldest, followed by three younger major sets striking NNW-SSE, N-S, and NNE-SSW. The younger fractures are nearly parallel to the present day maximum horizontal in-situ stress. Crack-seal mechanism (natural hydrofracturing) dominates initial fracture growth, some with several phases of partial to complete mineralization or coating, dominated by calcite, quartz, and dolomite. Aqueous and hydrocarbon gaseous and fluid inclusions are common in the fractures' mineral filling. The regional nature of in-situ stresses and natural fractures means their occurrence, orientation, relative dominance, and relative age and relative apertures are easier to predict and manipulate for well planning and completion, including hydrofracturing. Forward modeling shows that natural fracture network are not critically stressed under reservoir conditions but when subjected to massive hydrofracture stimulation they and the bedding discontinuities form the seeds for the growth of a complex hydrofracture network that potentially grows out of presumed stress-barriers. Lack of stress rotation around faults in wells supports the modeling results. Microseismic monitoring gives time-lapse (incremental) microseismic events of two types; random and linear patterns parallel to maximum horizontal in-situ stress and the predominant natural fracture trend. Bulk microseismic cloud has no unique link to fault trends mapped from high resolution borehole images. This finding challenges the usability of uncalibrated microseimic monitoring of massive hydrofracturing to map faults.     

Sociocultural institutions in Norwegian fisheries management

Many policymakers attribute the success of fisheries management regimes to the design and implementation of particular regulatory tools. While sound design and effective implementation are crucial elements of any successful regulatory action, fisheries policymakers and regulators should also account for the heterogeneous sociocultural institutions of partner communities. The success of fisheries policies relies on compliance and, ideally, cooperation (accepting policies, i.e. not protesting or otherwise strongly agitating against the system) from fisheries stakeholders. Even a policy that is sound in design and flawless in execution is at risk of failure if target stakeholders obstruct or otherwise undermine the system. This paper investigates how institutions, at various levels of scale and formality, play a role in determining the degree of compliance and/or cooperation that a fisheries management regime enjoys. In particular, it will examine the issue of Individual Vessel Quotas (IVQs) in Norway, and the response of fishing communities to the trade liberalization of IVQs.     

海上溢油粒子追踪预测模型中的两种数值方法比较

在海上溢油粒子追踪预测模型中,关键的是对拉格朗日微分方程的求解。本文首先通过数值实验比较了欧拉法和龙格-库塔法求解拉格朗日溢油轨迹微分方程的优劣,然后将其应用到2005年4月3日发生在大连附近的“ARTEAGA”油轮溢油事故的油膜粒子追踪模型中。数值实验和应用结果表明,在近岸不均匀流场下,用龙格-库塔方法解拉格朗日油粒子微分方程比用欧拉法求解精度高,用龙格-库塔方法模拟“ARTEAGA”油轮轨迹及其扩散范围与实际观测更为接近,而用欧拉法模拟溢油扩散的面积偏大。     

声电成像测井在北黄海盆地中生界油气勘探中的应用

北黄海盆地是海域油气勘探新区,经历了多期次的构造演化,地质条件复杂、勘探难度大.利用声电成像测井资料对该盆地东部坳陷某区块的岩性、层理类型、裂缝、古水流及地应力方向进行了分析研究.结果表明：区内中生界岩性主要为砂砾岩、细砂岩、粉砂岩和泥岩;泥岩段水平层理发育,砂岩段则多见楔状交错层理、板状交错层理、小型波状层理;下白垩统、侏罗系的古水流方向在不同并区差异小,总体上呈东偏南向;中生界裂缝不甚发育,多数集中在侏罗系,倾角普遍较大,主要分布于泥岩或泥质粉砂岩,多属无效缝;地应力分析结果指示,研究区最大水平主应力为近东西向.上述研究为该区进一步勘探部署提供了可靠的基础资料.     

平潭近岸海域浮子漂移轨迹及其数值模拟

平潭近岸海域岸线曲折,周边岛礁众多,海底地形复杂,是福建省海难事故的高发区.本研究建立了平潭近岸海域海上目标物漂移轨迹的预测系统,该系统通过风场和流场的数值模型获取海面动力环境信息,采用拉格朗日算法实现对海上目标物漂移轨迹的预测追踪.其中海流模型采用ROMS（regional ocean modeling system）模型构建,模型水平方向上最高分辨率为100m,垂向上分为16层,并考虑干湿边界,以体现复杂海岸线和水深地形.通过验证分析,潮位、流速和流向的模拟平均绝对误差分别为0.20 m、0.12 m/s和26°.通过平潭近岸2个浮子实验,结果表明,浮子漂移过程中受潮流和局地地形的影响明显,对漂移模型在平潭近岸海域的适用性进行初步验证,浮子模拟轨迹与实际漂移过程基本吻合,模拟时段内最大偏差距离为2.8km,系统可以为平潭近岸海域海上突发事故应急决策提供参考.     

Numerical Study of the Oil Spill Trajectory in Bohai Sea,China

Sixteen numerical experiments are conducted using the General NOAA Operational Modeling Environment (GNOME) to numerically study the oil spill trajectory in the Bohai Sea, China, for the purpose of providing information for the oil cleanup and disaster mitigation. High resolution coastline and topography data investigated by China's 908 Program are used to accurately describe the regional geographic feature of the Bohai Sea. Currents and waves required by GNOME are generated by the Hybrid Coordinate Ocean Model and Simulating Wave Nearshore, respectively. Experimental results show that oil spilled in different seasons and at different locations will result in completely different spilling trajectories, traveling distances, and polluting areas. Knowing that information comprehensively is vital to pollution control. Another important goal of this work is to provide users with simulated oil spill trajectory information through China Digital Ocean Prototype System (CDOPS), a grand marine information platform for managing, displaying, and public sharing of the data investigated by the China 908 Program. Users can obtain the trajectory, spreading, and potential impact area of the spilled oil through the oil spill module in CDOPS.     

基于复杂网络的海洋涡旋移动特征研究——以南海为例

海洋涡旋作为一种快速连续变化的海洋现象,如何分析和挖掘其移动特征成为当前海洋涡旋定量研究的重点。本文引入空间数据挖掘的社区网络划分方法,将涡旋过程看作复杂的移动网络,对涡旋移动的聚集性特征进行探索和分析。首先,以网格为统计单元对1992-2011年近20年南海海洋涡旋移动数据进行组织,基于图论模型构建了涡旋瞬时移动（TP）,涡旋移动起止点（OD）,涡旋最小描述距离的特征点移动网（MDL）和涡旋过程移动再生数据（RSP）4种状态的海洋涡旋的移动网络图;其次,采用基于快速模块度优化的区域划分方法分别得到4种状态下涡旋移动的聚集性区域;最后,利用弦图对区域内和区域间涡旋移动规律进行了可视化分析,发现海洋涡旋的RSP数据能够弥补原始涡旋移动数据在区域划分方法中呈现的数量不足的问题,能够在足够数据量的情况下,有效地发现从起点到终点的主要移动通道和涡旋移动的聚集性区域,这些区域反映了南海涡旋从其产生、发展到结束整个演化过程的聚集性特征。     

桩-网路堤位移应力分析及其应用

由于桩-网复合地基的结构形式比较复杂,难以采用解析法求得其应力和位移。利用有限差分法对某桩-网法路堤进行了数值模拟,并取得了较好结果。计算结果显示,桩间土沉降线为悬链线,与现场位移监测结果吻合较好;桩身弯矩和桩土应力反映了桩-网复合地基的一些受力机理。分析认为,桩间土沉降较大的主要原因是由土体本身压缩及桩侧弯引起的。