WRF模式中台风"启德"模拟对 参数化方案的敏感性分析

为准确模拟台风路径和强度,采用WRF模式比较不同微物理过程和积云对流过程参数化方案对台风路径和强度模拟的影响,并基于集合预报方法考虑对台风预报系统误差进行优化。选用4种微物理过程方案和3种积云对流参数化方案,针对1213号台风“启德”进行模拟,结果表明不同的参数化方案对台风路径和强度的预报结果有明显影响,积云对流过程参数化方案相对于微物理过程参数化方案更加敏感。基于不同参数化方案扰动成员的集合平均预报方法,对于台风路径和强度的模拟误差均有明显改善,台风路径误差随时间增幅较小,其结果优于全部12个单方案试验的模拟结果;从台风强度方面来看,基于集合预报方法模拟得到的台风强度变化趋势与实况结果一致,且误差较小,优于大多数试验方案。结果表明:采用不同微物理过程和积云对流过程参数化方案的组合构建的集合预报模型,对于台风路径和强度的模拟均有一定程度改善,减小了采用不同参数化方案产生的路径不确定性,使其在台风“启德”的路径模拟上与实况更为接近,可为提升台风预报能力提供科学参考。     

穿越副高北上的台风路径预报方案

本文提出一个穿越副高北上的台风路径预报方案。在较严格的初始状态条件下,方案应用环境场的多种参数及其导出因子和统计天气预报方法,进行穿越副高北上台风的12～72小时路径客观预报,预报试验表明,该方案对穿越副高北上台风的路径预报具有一定的技巧。     

舟山渔港风暴潮模拟分析

渔港风暴潮研究对防灾减灾具有重要意义。本文构建了舟山海域嵌套网格的风暴潮模型,经天文潮与风暴潮实测资料验证效果良好。设计5个方向共14条台风路径,计算了2017年8月8?12日大潮期12～17级台风下舟山渔港的风暴潮位。结果表明,由于向岸风作用南侧SE向比北侧E向登陆台风所造成的最高风暴潮位高35.7%,差值可达82 cm;对于两端通海的舟山渔港,南侧0.5R处登陆的SE向台风,风向与东口门朝向一致而跟渔港走向斜交,有利于水体进入并滞留,此时风暴潮位最高。南侧12级台风下ESE、SE、SSE发生漫堤,而北侧登陆台风无漫堤风险,沉降等原因造成海堤防台能力两头低于中段;数值试验显示,若在小干岛东侧设置丁坝,可将17级台风作用下的漫堤概率由26.23%减为10.66%。     

导管架海洋平台沉降监控

导管架海洋平台在长期使用中存在着桩基础沉降的问题。海上固定式结构物由于在海面上很难找到固定的参考点,因此很难采用常规土木工程中的沉降测量方法对沉降问题进行测量。根据土壤的压缩性质以及桩基沉降给平台带来的危害程度,制定了沉降的三级监控方法。通过对平台上部总荷载、单桩荷载以及不均匀沉降的监测来监控平台的沉降情况,并在渤海某平台上进行了实际应用。通过采用光纤光栅等先进的监测手段以及合理的监测方案,实现了导管架平台沉降的三级监控,实际应用效果良好。     

基于散射计风场数据的台风强度诊断方法——以海洋二号卫星数据为例

本文提出了一种基于散射计风场数据的台风定强方法。该方法定义了台风所在海区的一个圆形区域上的风速平均值来对台风进行定强,并使用海洋二号卫星散射计历史数据对该方法进行了验证。验证结果表明,该台风定强方法可以克服散射计反演台风风速过低的问题。与台风强度监测的历史记录比较的结果显示,在台风强度低于"强台风"这一强度等级时,该方法能够有效估算台风强度。     

“南浮一号”在珠江口外陆架投放简况

海洋浮标“南浮一号”于1984年8月底,在珠江口外陆架海区水深约80米处投放,以求收集台风下的水文气象资料,为海洋石油开发服务。 在如此水深的海域投放大型浮标,不能抛锚作业,难度较大,在国内是首次。投放前经试验找到较好的拖曳点,并慎重制定了稳妥可靠的方案。浮标开始拖航时,8410号强台风已在菲律宾造成严重灾害,即将进入南海。浮标以7节拖航出珠江口经万山群岛附近海域时,涌浪高达2米多,以至尼龙拖缆断裂,立即紧急处理,并抢在台风到来之前,到达预定位置成功投放。     

柔性结构养殖网箱的抗风浪性能试验报告

本文报道了以柔性绳索作为承爱和传递波浪作用力的主结构的柔性养殖网箱的抗风浪性能试验结果。在9914号特大台风的正面袭击下，这种网箱能基本保持完好，表明它具有十分优越的抗风浪性能。通过对试验环境的初步分析表明，该网箱系统能抵抗住海面波高在4．7米以下、波长在76．95米以内的台风浪袭击，可满足福建省大部分近海海面在十年一遇台风重现期条件下的近海网箱抗风浪养殖的要求。     

基于蚁群优化的近岸影像水边线变化分析方法

由于近岸视频监测技术具有构建成本低、时空分辨率高的特点,近年来已成为海岸动态监测的互补手段。在近岸视频监测中,水边线可作为岸滩边缘位置变化的替代指标,受复杂海滩地形及不规则的波浪及潮汐变化影响,如何从视频图像中准确检测水边线是近岸视频监测所面临的挑战问题之一。本文针对传统图像处理方法在水边线提取中存在的效率不高和抗噪声能力差等问题,将CIELab颜色模型和蚁群优化算法相结合,对台风风暴潮期间石老人海滩的水边线进行提取和定量分析,并与传统算法进行对比。对青岛石老人海滩2011年台风期间的实时影像资料分析结果表明,与传统的提取算法相比,本文提出的方法在数字视频影像的水边线监测应用中可靠性高,并具有良好的细节呈现能力和抗边缘噪声能力,适用于弱边缘水边线的提取。分析结果验证了本方法在极端天气条件下对视频影像中水边线动态变化的自动提取可行性,对构建长时序海滩岸线动态变化影像自动分析系统具有较好的应用价值。     

WRF大气模式与台风经验模型在超强台风“山竹”过程重构中的比较分析

通过中尺度气象研究与预报模式WRF（weather research and forecasting）和两种台风经验模型重构了2018年影响我国珠江口地区的超强台风“山竹”过程中的气压和风矢量场,在台风最佳路径数据的基础上开展了方法间的比较,并与香港、澳门和深圳三个国际机场的实测数据进行了对比分析,验证了三种模拟方案模拟台风“山竹”的可靠性。利用非结构网格半隐式跨尺度海洋模式SCHISM （semi-implicit cross-scale hydroscience integrated system model）,将三种模拟气压和风场作为驱动场输入风暴潮模式中进行增水模拟试验,比较了它们在赤湾、三灶、横门和黄埔四个测站风暴潮增水中各自的效果,并进一步验证了WRF模式和两种经验模型模拟台风“山竹”的有效性。综合来看, WRF大气模式对气压、风速、风向及风暴增水模拟效果最佳,如果进一步优化该模式的各种参数化方案,可能还能提高其精度。如果不具备使用WRF大气模式的条件,台风经验1模型也是一个完全可以接受的、简单快捷的方案。     

WRF Hybrid方法同化HY-2A散射计风资料在台风“菲特”预报中的应用

选取台风"菲特"(Fitow,201323)临近登陆过程为试验个例,在WRF模式基础上,采用4种不同的初始化方案,对台风"菲特"进行了72 h预报试验,并分析了模式的初始化对预报效果的影响。试验结果表明,对于台风路径的预报,使用集合平均作为初始场进行预报,预报结果相对直接使用GFS资料作为初始场进行预报的结果有明显改善,使用3DVAR同化方法,将HY-2A卫星散射计风场资料同化到集合平均的初始场中,台风路径预报进一步有所改善,而使用Hybrid同化方法将HY-2A卫星散射计风场资料同化到集合平均的初始场中,台风路径进而又有明显改善;但是在台风强度方面的预报,4种初始化方案效果不相上下。     

Evaluation of Effective Depth of PVD Improvement in Soft Clay Deposit: A Field Case Study

This article presents a case history of determination of effective depth of prefabricated vertical drains (PVDs) under embankment loading on a very soft clay deposit in central China, near Jiujiang, Jiangxi Province. The height of the embankment was 5.3 m and construction time was about one year. The PVDs were installed to a depth of 8.5 m at a spacing of 1.5 m in a triangular pattern. Field observations and the finite element method (FEM) were employed to analyze the performance of the soft deposit during embankment construction. The influential depth of the embankment loading was evaluated based on settlement, excess pore pressure, and stress increase in subsoil, both from the observed data and FEM analysis. The effective PVD depth was determined in the following ways: (1) the depth of 5% subsoil settlement of surface settlement; (2) vertical stress increase in subsoil of 25% in-situ stress; and (3) consolidation time/PVD depth relation by FEM. Based on the analysis, the effective depth of PVDs was determined to be between 10 and 12.8 m for this field case.     

基于海啸感应电磁场的海啸监测研究与应用现状

早期的海啸监测系统主要依赖地震监测网或海底压力计阵列网,但都存在诸如建设和维护成本高、监测范围有限等问题。对海啸的实际观测和模拟发现,广泛分布的海底电缆能够反映海啸运动产生的感应电磁场,由此发展出了更为便捷和经济的海啸感应电磁场监测方法。本文介绍了海啸感应电磁场的理论推导过程、不同海啸速度模型,以及对不同海底地形类型的海啸感应电磁场解析解的研究进展。对比分析海啸感应电磁场的电压、扰动磁场、矢量电磁场三种海啸电磁监测方法的优缺点后认为,矢量电磁场监测具有测量海啸传播方向的优势,利用矢量电磁测量结合现有的海啸监测系统能更快更准更实时地预警海啸。     

Evaluation of the Strength Increase of Marine Clay under Staged Embankment Loading: A Case Study

This article presents a case history of the performance of a full-scale test embankment constructed on a marine soft clay deposit improved by prefabricated vertical drains (PVDs) in the east of China. For analyzing the subsoil behavior, a 2D FEM model is established, in which the PVD-improved effect is considered by a simplified method of equivalent vertical hydraulic conductivity. The calculated results can predict the settlement behavior well; however, the FEM gives an underestimate for the value of excess pore pressures and it predicts similar values for the dissipation rate of excess pore pressures. The measured undrained shear strength of subsoil, C_u, is compared with the predicted value based on Ladd’s empirical equation and the Modified Cam-Clay model (MCC). The shear strength predicted by Ladd’s equation agrees well with the measured value, whereas the MCC overestimates the ability to improve subsoil shear strength during consolidation. The undrained shear strength of subsoil, C_u, increased as the construction progressed, and the shear strength incremental ratio, ΔC_u/Δp′, decreased slightly with the degree of consolidation, U.     

Numerical approach to predict ground displacement caused by installing a horizontal jet grout column

When horizontal jet grouting is conducted in fine-grained soils, the injection of large volumes of fluid with high injection pressure into the ground may cause ground surface upheaval and the lateral movement of subsoil. This paper provides a numerical approach to calculate the ground displacement caused by installing a horizontal column based on determination of the influencing radius of injection pressure and the volumetric expansion strain caused by fluid injection. During the course of this study, the relationship between the influencing radius, column radius, volumetric expansion strain, and jetting parameters is established. The proposed numerical approach is applied to analyze a case history conducted in Shanghai soft soil deposits, which include the monitoring of vertical displacement of the ground surface and lateral displacement of the subsoil during construction. A comparison of the results between the simulated values with the Mohr Coulomb model and field data demonstrates that the numerical approach can yield a reasonable prediction of these field measurements when the influencing radius is six times the radius of the column. The influence range of the horizontal jet grouting activity is also discussed by numerical analysis with respect to two soil models (the Mohr Coulomb model and the hardening soil model).     

Evaluation of Inner Soil Pressure Acting on Opened Bottom Cylindrical Structure

1 .IntroductionAnopenedbottomcylinderisathinshellstructureplacedonarubblebaseorembeddedinasoilfoundation .Itiswidelyusedintheconstructionofwharves ,breakwatersandotheroceanprojects.Thestructureisusuallyfilledwithgranularmaterialstoensurethestabilityofthestructurealongwiththeweightofthecylinder.Hence ,itisconsideredasagravitytypeofstructure .However,thesettlementofthecylinderisdifferentfromthatofthetraditionalgravitytypeofstructureandsodoesthedistribu tionofinnersoilpressureovertheopenedbottom…     

A Combined Dry Jet Mixing-Prefabricated Vertical Drain Method for Soft Ground Improvement: A Case Study

A remarkable combined dry jet mixing (DJM) and prefabricated vertical drains (PVDs) method was used to enhance the performance for soft ground improvement. In the combined method, PVDs are first installed and then DJM columns are installed between the PVDs at larger spacing. This combined method improves the effectiveness of the ground improvement and creates a more economical solution. This paper presents a case study of the combined method for marine clay improvement in Lianyugang of China. The excess pore water pressure in soils created by the installation of DJM columns with and without PVDs was monitored and compared. In situ standard penetration tests were conducted in the DJM columns and before-and-after piezocone penetration tests were performed in soils surrounding the columns. Long-term settlement monitoring under embankment loading was carried out for the ground improved by combined method and DJM method alone. The field tests, settlement monitoring and economic benefit analysis results demonstrated that the DJM-PVD method is technologically sound and cost-effective as compared with the conventional DJM method.     

Numerical analysis and centrifuge modeling of shallow foundations

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.     

Field measurements and monitoring of wastewater discharge in sea water

This paper reports a study of the field measurements and monitoring of wastewater discharge in sea water at Bari East (Italy). A wastewater sea outfall system is an integral and fundamental part of each wastewater treatment with ultimate sink in the sea water. The design of a water treatment plant and wastewater outfall must take into account the use of the environmental water, the values of physicochemical parameters to be respected in order to safeguard the use itself and the quality of the environmental water where wastewater is issued. In the present study measurements of sea current velocity components were carried out with a VM-ADP (Vessel-Mounted Acoustic Doppler Profiler). Salinity, wind directions and velocities were assessed with, for one survey, the total faecal coliforms and other biochemical parameters. It was emphasized that the measurements necessary for monitoring cannot be concentrated in the wastewater outfall pipe zone only, but should be extended to a neighbouring area of the outfall pipe, with an extension depending on the wastewater discharge, the polluting charge and the magnitude of the sea currents and the winds typical of the zone of interest. The analyses presented in this paper confirm that the sea zones close to the wastewater outfall pipe are particularly sensitive and vulnerable. Such results must be considered in the planning of a wastewater outfall pipe.     

High-resolution field measurements and numerical modelling of intra-wave sediment suspension on plane beds under shoaling waves

Intra-wave sediment suspension is examined using high-resolution field measurements and numerical hydrodynamic and sediment models within 120 mm of a plane seabed under natural asymmetric waves. The detailed measurements of suspended sediment concentration (at 5 mm vertical resolution and at 4 Hz) showed two or three entrainment bursts around peak flow under the wave crest and another at flow reversal during the decelerating phase. At flow reversal, the mixing length was found to be approximately double the value attained at peak flow under the crest. To examine the cause of multiple suspension peaks and increased diffusion at flow reversal, a numerical “side-view” hydrodynamic model was developed to reproduce near-bed wave-induced orbital currents. Predicted currents at the bed and above the wave boundary layer were oppositely directed around flow reversal and this effect became more pronounced with increasing wave asymmetry. When the predicted orbital currents and an enhanced eddy diffusivity during periods of oppositely directed flows were applied in a Lagrangian numerical sediment transport model, unprecedented and extremely close predictions of the measured instantaneous concentrations were obtained. The numerical models were simplified to incorporate only the essential parameters and, by simulating at short time scales, empirical time-averaged parameterisations were not required. Key factors in the sediment model were fall velocities of the full grain size distribution, diffusion, separation of entrainment from settlement, and non-constant, but vertically uniform, eddy diffusivity. Over the plane bed, sediment convection by wave orbital vertical currents was found to have no significant influence on the results.     

水体颗粒后向散射系数测量一致性对比实验研究

颗粒后向散射系数是水体最重要的固有光学参量之一,也是海洋水色卫星遥感的核心参数。现场准确测量水体颗粒后向散射数据,对于水色遥感模型构建以及水色遥感产品真实性检验至关重要。本文针对常用的3种水体颗粒后向散射系数原位测量仪(HydroScat6,VSF3和BB9),通过比测实验,对三者测量结果的一致性进行了比较分析。结果表明,在清洁水体中3种仪器对颗粒后向散射系数测量具有较好的一致性;但在浑浊水体中,HydroScat6和BB9测量值会比VSF3高,三者偏差显著增大。同时,数值模拟和实验结果均表明,颗粒形状会对测量结果产生影响,3种仪器对球形颗粒的后向散射系数测量结果的一致性显著好于野外颗粒结果。