Nonlinear Behaviour of Coflexip Risers

A modified Newton-Raphson iterative technique is formulated for obtaining the static configuration of the Lazy "S" flexible marine riser between the floater and mid-arch buoy under its submerged self weight and the applied top tension. The geometrically non-linear problem is solved by finite difference with the above technique. The problem is formulated as a regular boundary value problem with specified moments and deflections at both ends. Usually the bending stiffness of the flexible riser made of Coflexip pipe is very low. By use of the above analysis, several flexible riser configurations are analyzed and their characteristic behaviors are investigated. Also, changes in the riser characteristics due to quasi-static motion of the floater end are estimated for the safety of the riser layout.     

Tsunami Wave Interaction with Data Buoys

To plan for proper mitigation measures, one should have an advanced knowledge of the phenomenon of tsunami propagation from the deep ocean to coastal waters. There are a few methods to predict tsunamis in the ocean waters; one method is the effective use of data buoy measurements. Although data buoys have been used along the Indian waters there has been a tremendous growth in the number of buoy deployment recently. Under the National Data Buoy Programme (NDBP) of India, the 2.2 m diameter discus data buoys were deployed along the east and west coasts of India for measuring meteorological and ocean parameters. It would be advantageous if these buoys could be efficiently used to measure rare events such as tsunamis. Understanding the dynamic behavior of the buoy is of prime importance if a tsunami warning system is to be successful. This may be accomplished through experimental or numerical studies. A comprehensive experimental study has been conducted to understand the dynamic behavior of a wave rider buoy exposed to a variety of waves. It is common that tsunami waves are represented in terms of shallow water waves, namely solitary and cnoidal waves. Hence, in the present study, the discus type data buoy is scale modeled and tested under the action of solitary and cnoidal waves in the laboratory. The time histories of wave elevations, as well as heave and pitch motions of the buoy model, were analyzed through a spectral approach as well as through wavelet transformations. The wavelet approach gives more detailed insight into the spectral characteristics of the buoy motion in the time scale. The harmonic analyses were performed for the cnoidal wave elevations and subsequent motion characteristics that give an insight into the energy variations. The details of the model, instrumentation, testing conditions and the results are presented in this paper.     

Investigation on the Oscillating Buoy Wave Power Device

An oscillating buoy wave power device (OD) is a device extracting wave power by an oscillating buoy. Being excited by waves, the buoy heaves up and down to convert wave energy into electricity by means of a mechanical or hydraulic device. Compared with an Oscillating Water Column (OWC) wave power device, the OD has the same capture vvidth ratio as the OWC does, but much higher secondary conversion efficiency. Moreover, the chamber of the OWC, which is the most expensive and difficult part to be built, is not necessary for the OD, so it is easier to construct an OD. In this paper, a nu-merical calculation is conducted for an optimal design of the OD firstly, then a model of the device is built and, a model test is carried out in a wave tank. The results show that the total efficiency of the OD is much higher than that of the OWC and that the OD is a promising wave power device.     

国产海洋气象漂流观测仪在台风观测中的应用分析

介绍了由我国自主研制的、基于北斗导航通信卫星的、集海洋水文要素和气象要素一体观测的、在恶劣海况条件下能进行连续、可靠观测的海洋气象漂流观测仪,及其在多个海域开展实际的外海观测试验情况。2017年8月20日至9月5日,三台漂流观测仪在广东博贺海洋气象综合试验基地,经历了2017年第13号台风天鸽和第14号台风帕卡两次台风天气过程。对试验期间获取的台风天气过程中气温、气压、海温等观测数据的分析表明,漂流观测仪所获得的观测数据与相关国家级业务观测站点的观测数据具有较好的相关性,揭示了台风天气过程的明显特征,并表现出合理、清晰的日变化特征。上述试验表明,国产海洋气象漂流观测仪已具备在恶劣海况下进行实际观测的能力。     

Validation of SWH and SSHA from SARAL/AltiKa Using Jason-2 and In-Situ Observations

The focus of this study is the validation of significant wave height (SWH) and sea surface height anomaly (SSHA) obtained from the first Ka-band altimeter AltiKa onboard SARAL (Satellite for ARGOS and Altimeters). It is a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales (CNES). This is done using in-situ observations from buoy and Jason-2 measurements. Validation using buoy observations are at particular locations while that using Jason-2 altimeter is an attempt towards global validation of Altika products. The results clearly indicate that the SARAL/AltiKa provide high-quality data and the errors are within a predefined range of accuracy. A parallel validation of SWH from other altimeters, which monitored ocean since last decade, like EnviSAT and Jason-2 was also performed with buoy observations. The results clearly show that the accuracy of AltiKa SWH is much better than EnviSAT and comparable to reference mission Jason-2. The accuracy is quite good for the calm sea while in the rough seas the accuracy degrades some. The inter-comparison of SARAL/AltiKa SSHA with Jason-2 indicates a fair match between them. These validation exercises demonstrate the high quality of AltiKa products, usable for practical applications.     

基于Argo浮标数据的星载微波辐射计Aquarius数据产品质量评估

Aquarius是专门用于海洋盐度监测的L波段辐射计,于2011年6月发射入轨,目前已进入业务化运行阶段。本文以太平洋为研究区域,利用Argo盐度现场数据对星载微波辐射计Aquarius的2012年2级数据产品质量进行了分析与讨论,结果表明:与Argo数据比较,Aquarius数据盐度存在0.1的负偏差,标准差约为0.7,升轨和降轨数据差异不明显;受亮温陆地污染和无线电射频干扰的影响,近岸海域反演误差较大;海面温度较高的低纬海域反演结果优于中纬度海域;受亮温敏感性及粗糙海面发射率模型的影响,Aquarius在低温水域以及高风速条件下盐度反演误差较大,标准差可达1以上。     

IMPROVEMENT OF OCEAN DATA ASSIMILATION SYSTEM AND CLIMATE PREDICTION BY ASSIMILATING ARGO DATA

The Argo(Array for Real-time Geostrophic Oceanography) data from 1998 to 2003 were used in the Beijing Climate Center-Global Ocean Data Assimilation System(BCC-GODAS). The results show that the utilization of Argo global ocean data in BCC-GODAS brings about remarkable improvements in assimilation effects. The assimilated sea surface temperature(SST) of BCC-GODAS can well represent the climatological states of observational data. Comparison experiments based on a global coupled atmosphere-ocean general circulation model(AOCGM) were conducted for exploring the roles of ocean data assimilation system with or without Argo data in improving the climate predictability of rainfall in boreal summer. Firstly, the global ocean data assimilation system BCC-GODAS was used to obtain ocean assimilation data under the conditions with or without Argo data. Then, the global coupled atmosphere-ocean general circulation model(AOCGM) was utilized to do hindcast experiments with the two sets of the assimilation data as initial oceanic fields. The simulated results demonstrate that the seasonal predictability of rainfall in boreal summer, particularly in China, increases greatly when initial oceanic conditions with Argo data are utilized. The distribution of summer rainfall in China hindcast by the AOGCM under the condition when Argo data are used is more in accordance with observation than that when no Agro data are used. The area of positive correlation between hindcast and observation enlarges and the hindcast skill of rainfall over China in summer improves significantly when Argo data are used.     

浙江省海洋水质监测浮标设计与实现

作为一种高技术监测手段,海洋浮标可实现现场自动监测而不受恶劣海况的影响,近年来得到了广泛的重视和快速发展。文中介绍了浙江近岸海域海洋水质监测浮标的结构设计和自动监测实现。浮标设计为生态浮标、海滨浮标和专项浮标3种类型,由浮体、标架、供电设备、防护设备、锚系、传感器、数据采集传输、电子/电池舱、岸站接收系统等9个部分组成。浮体设计为圆饼形,浮体下方正中安装稳定锤以保证具备足够的稳定性。供电设备由太阳能电池板、大容量蓄电池组成,可保障海上30 d连续阴雨天气、恶劣海况下的不间断供电。浮标经喷防污漆、牺牲阳极保护、裹铜皮、加过滤网和人工清除等5种方法防腐、防污处理后投放入海,采用常规维护、应急维护和年度维护等3种方式保障浮标系统运行稳定。投放后可实现对标浮所在海域水质、气象、生态等参数的连续、实时、自动监测。最后对浮体直径设计和浮标投放点选址提出了建议和要求。该设计可为其它类似区域的水质监控提供良好的参考。     

Variations of sea ice temperature from CHINARE 2003 and its application on sea ice model evaluation

Variation of vertical profiles of sea ice temperature and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea as part of the 2003 Chinese Arctic Research Expedition.The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September,propagated down through the ice,reaching the bottom of the ice in December,and continued throughout the winter.In winter 2003/04,some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea.It is found that the melt season at the buoy site in 2004 was about 15% longer than normal.The buoy observed vertical ice temperature profiles were used as a diagnostic for sea ice model evaluation.The results show that the simulated ice temperature profiles have large discrepancies as compared with the observations.