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锚泊船只在受到海流、风、海浪等外力作用时其运动规律是很复杂的。大体有下列几种运动:船只绕锚定点的回转运动;绕锚链孔的旋转运动;摇艏运动;纵横向摇摆;升沉运动等。这些运动以各种方式影响测流结果。另外流体绕流现象改变了船只周围的流态,船体磁场对海流计的流向传感器也有影响。一般从事海洋调查的人员,对这些情况是很熟悉的,应当设法消除或减少这些影响。我们的实验表明即使在风平浪静的2~3级海况,这些影响也不容忽视,这时的流速误差可达20%之多;流向误差可达±10°。在实验中我们观测了船艏向,锚链的方位角及入水角参数的时间变化,并作了这些因素对海流测量影响的初步分析。 相似文献
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福建省沿海冬半年东北大风的数值预报释用方法研究 总被引:2,自引:0,他引:2
《海洋预报》2015,(5)
基于福建省冬半年沿海32个自动站的极大风观测资料和WRF、EC细网格以及T639 3种模式预报的10 m风场资料,将模式预报的风速与观测资料进行对比分析,结果表明:WRF和EC细网格的预报效果较好,有可参考性,T639可参考性不高。模式预报结果相比实况极大风速偏小,预报平均绝对误差由沿海向内陆逐渐减小,由中部向南北逐渐减小。择取预报效果较好的WRF和EC细网格模式,对沿海代表站点进行风速集成,建立集成预报方程,并进行集成订正。误差订正后,与误差较小的WRF模式相比,预报准确率提高了10%左右,改善效果显著,为提高福建省沿海冬半年东北大风的预报准确率提供定量的预报方法。 相似文献
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讨论了使用Froude法和Faltinsen法识别线性和非线性阻尼系数时的系统误差。通过回顾两种方法的推导过程,论证了方法的内在假设,并量化两种方法的系统误差。为减少识别过程误差,文中提出了直接积分法,并依据数值与试验数据,讨论了3种识别方法识别结果。结果表明,Froude法相比于Faltinsen法能更好地预报线性和非线性阻尼系数。对于低阻尼浮体问题,Froude法和Faltinsen法可以给出相对准确的预测,而对于强阻尼浮体问题,Froude法与Faltinsen法在确定的线性和非线性阻尼系数中会给出大于5%的系统误差,而直接积分法展示了较高的识别精度。 相似文献
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中国沿海海表温度均一性检验和订正 总被引:4,自引:1,他引:3
利用惩罚最大T检验(Penalized Maximal T test,PMT)方法,选取均一的邻近气象站为参考站,基于月平均地面气温(SAT)资料,利用相关系数权重平均方法构建参考序列,同时结合元数据信息,对1960-2011年中国沿海27个海洋观测站月平均海表温度(SST)进行了均一性检验与订正,并分析了造成海表温度序列非均一的主要原因。结果表明,中国沿海海洋台站海表温度资料存在较为严重的非均一性问题,几乎所有的台站都存在断点,仪器变更(包括人工观测转自动观测)(占总断点数的52.4%)和迁站(占总断点数的33.3%)是造成序列非均一的主要原因。整套资料负订正量所占比例较高,这种负订正量与人工转自动观测后海表温度观测值偏低有密切关系。这也使得订正后中国沿海平均海表温度趋势与订正前存在明显差异,订正后中国沿海海表温度呈明显的加速上升趋势。 相似文献
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近海风速预报在沿海防灾减灾、航运安全、风能评估等方面具有重要应用。本文基于欧洲中期天气预报中心数值预报 (ECMWF) 数据,将最优 TS 评分 (OTS) 与频率匹配 (FMM) 两种方法应用于江苏近海风速预报订正,对比了两种订正
方法的优缺点,分析了不同时间训练样本量以及空间站点观测资料数量对订正效果的影响。结果表明:在相同长度的训练期下,风速等级越小,时间训练期样本越多,预报订正值越稳定;对于 7 级以上高风速等级的预报,OTS 与 FMM 的 TS 评分差异不大, 但 FMM 订正更加稳定且频率偏差 (BIAS) 更接近 1;扩充站点观测资料可有效提升预报订正性能;对于 7 级以上灾害性大风,最佳的订正方案是采用 FMM 方法结合全年时间训练样本和扩充的站点观测资料。此外,本文还对比了不同风速情形下,订正前后 BIAS 和 TS 评分对于时间训练样本量、空间站点观测数量以及订正方法 (OTS 和 FMM) 的敏感性的相对大小。 相似文献
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A new method for weakening the combined effect of residual errors on multibeam bathymetric data 总被引:2,自引:0,他引:2
Jianhu Zhao Jun Yan Hongmei Zhang Yuqing Zhang Aixue Wang 《Marine Geophysical Researches》2014,35(4):379-394
Multibeam bathymetric system (MBS) has been widely applied in the marine surveying for providing high-resolution seabed topography. However, some factors degrade the precision of bathymetry, including the sound velocity, the vessel attitude, the misalignment angle of the transducer and so on. Although these factors have been corrected strictly in bathymetric data processing, the final bathymetric result is still affected by their residual errors. In deep water, the result usually cannot meet the requirements of high-precision seabed topography. The combined effect of these residual errors is systematic, and it’s difficult to separate and weaken the effect using traditional single-error correction methods. Therefore, the paper puts forward a new method for weakening the effect of residual errors based on the frequency-spectrum characteristics of seabed topography and multibeam bathymetric data. Four steps, namely the separation of the low-frequency and the high-frequency part of bathymetric data, the reconstruction of the trend of actual seabed topography, the merging of the actual trend and the extracted microtopography, and the accuracy evaluation, are involved in the method. Experiment results prove that the proposed method could weaken the combined effect of residual errors on multibeam bathymetric data and efficiently improve the accuracy of the final post-processing results. We suggest that the method should be widely applied to MBS data processing in deep water. 相似文献
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为完善目前走航ADCP观测资料质量控制尚未形成统一流程的问题,将走航ADCP观测资料质量控制归纳为船速获取、声速校正、偏角校正以及剖面数据处理四个主要步骤,并制定了一套较为系统的走航ADCP观测资料质量控制流程。以渤海辽东湾红沿河核电站周边海域船载走航ADCP观测为例,按照提出的流程进行走航ADCP观测资料的质量控制。通过对比原始观测数据,质量控制后的结果表明u分量流速剔除了23.56%的低可信度数据,而v分量流速剔除了25.96%的低可信度数据。10 m与15 m水深处的质量控制前后的流速-频数直方图表明,本文提出的流程能有效地降低观测随机性的影响。 相似文献
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Some errors and noises are often present in multibeam swath bathymetric data. Echo detection error (EDE) is one of the main errors. It causes the depth error to become bigger in outer beams and looks like sound refraction. But depth errors due to EDEs have a trumpet-shaped appearance, instead of a curved appearance that is caused by the sound refraction errors. EDEs, including systematic acoustic signal detection errors and internal noises, cannot be removed during the correction of sound refraction. It causes depth inconsistencies between adjacent swaths and degrades precision of outer beams. Sometimes, the bathymetric errors caused by EDEs do not even meet the requirements of IHO (International Hydrographic Organization). Therefore, a post-processing method is presented to minimize the EDEs by filtering outliers and compressing outer beams of multibeam bathymetric data. The outliers caused by internal noises are removed by an automatic filter algorithm first. Then the outer beams are compressed to reduce systematic acoustic signal detection errors according to their depths, the calculated depth line and standard deviations (SDs). The automatic filter process is important for calculating the depth line. The selection of inner beams to calculate the average SD of beam depths is crucial to achieving compressing goals. The quality of final bathymetric data in outer beams can be improved by these steps. The method is verified by a field test. 相似文献
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Guan-Lin Ye Chao-Jun Wu Jian-Feng Wang Jian-Hua Wang 《Marine Georesources & Geotechnology》2017,35(2):170-175
Triaxial test with local displacement transducers is an effective technique to obtain the small-strain stiffness of soils. Many previous studies provided feasible solutions for reducing or avoiding potential sources of error in conventional triaxial tests. However, little literature gave out detailed explanations on how to identify those potential errors from the measured testing data and corresponding solutions. Therefore, nowadays, it is still not easy for a new user to gain proficiency in such kind of advanced tests. In this article, by conducting triaxial tests featured with Hall effect transducer on Shanghai soft marine clay, it is found that the influence of the specimen misalignment to the measured small-strain stiffness cannot be neglected. The typical symptom of specimen misalignment, namely the tilting of specimen, was described carefully. An improved connection between top cap and load cell was applied to overcome the problem. The new connection can reduce the disturbance to specimen in terms of both force and displacement. It can be applied to both isotropic and anisotropic consolidated triaxial tests. 相似文献
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海洋的盐度观测对于气候和海洋科学的研究有重要的意义,盐度的卫星遥感观测需要估计各种因素带来的误差影响。本文基于海面微波辐射理论和海水相对电容率等模型,采用蒙特卡洛模拟方法研究了在盐度遥感中温度误差、仪器误差以及风速误差对于后续的盐度反演的影响。通过计算温度误差产生的盐度误差,并与敏感性方法的对比发现,在低温低盐时温度误差对盐度反演误差的影响较大,2种方法的偏差较大;而在高温高盐时温度误差对盐度反演误差的影响较小,2种方法的偏差较小。辐射计仪器噪声对盐度误差的影响普遍在0.1psu以上,在低温低盐时可达0.5psu以上。风速误差对盐度反演误差的影响在水平极化状态下随入射角增大,在温度低于20℃时普遍超过1psu;在垂直极化状态下随入射角先减小后增大,在温度低于20℃以及较小的入射角下误差也会超过1psu。对误差的综合分析发现,采用垂直极化状态在高温时这2种误差的影响较小。研究发现,当入射角是45.6°和垂直极化状态下,对于3种典型海面状态(35℃和35psu,20℃和35psu,5℃和30psu),反演的盐度反演误差可达到0.162,0.153和0.444psu,达到了卫星单次扫描对盐度反演的误差要求。 相似文献
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在海洋磁力测量中,因受测量环境及各项改正的残余量等因素的系统性影响,不同测线间存在着不同程度的系统差,这种测线系统差会使测区磁场水平不统一,导致磁异常等值线图失真。为此,研究了基于虚拟检查线的海洋地磁测量数据调差方法,该方法尝试在不使用检查线数据情况下,沿垂直于测线方向选取一定数量的虚拟检查线,根据测线数据拟合出各条虚拟检查线上场的分布规律,并将测线方向拟合前后残差的平均值作为各条测线上的测线系统差,对各条测线数据进行改正。仿真计算与分析表明:对于磁异常变化较平缓的测区,该方法可以有效消除测线系统差;当磁异常变化剧烈时,该方法可以部分消除测线系统差。 相似文献
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CODAS系统搭配相应质量控制参数,用以识别ADCP在复杂测流环境下测得的可疑或错误流速单元和剖面.通过水跟踪和底跟踪,CODAS系统可有效获取仪器自带数据处理软件vmdas、winriver无法修正的系统误差.本研究采用该系统对厦门湾走航ADCP测量数据做后续质量控制,所得相应系统误差如下:旋转角度偏差ΔФ=3.2°,幅值修正因子β=0.98.此外,以底跟踪测得流速为准确值,参考GPS数据经过系统误差订正后,流速精度显著提高,平均误差订正前后分别为28.9cm/s和11.6 cm/s.最后,结合现场数据采集工作与数据质量控制过程,总结数据质量问题一般特征并提出改进建议. 相似文献