基于卫星漂流浮标轨迹的东海边界交换估算方法研究          下载免费PDF全文

武则州  周锋 《海洋学研究》2018,36(1):27-34

东海陆架斜坡和台湾海峡是我国东部近海从大洋和南海获取热量、盐量和营养盐的两个主要边界。本文建立了一个不规则分布漂流浮标轨迹的网格化处理方法和跨边界交换估算方法。该方法得到的漂流浮标轨迹累计次数再现了黑潮主轴位置并表明主轴两侧浮标存在显著的跨陆坡交换现象。浮标轨迹的统计结果揭示了东海陆坡上水体交换具有显著的区域性,即陆坡上存在7个主要交换区,3个交换区以入流为主,另4个交换区以出流为主。研究也表明跨东海陆坡交换具有明显的季节变化特征,秋季交换最剧烈且入流最显著,春季最弱。穿越台湾海峡的交换主要以北向入流为主,海峡东侧的交换更加明显,一年之中夏季最显著,春、冬季最弱。  相似文献   

不同插值方法对GPS时间序列的影响分析          下载免费PDF全文

杨登科 《全球定位系统》2019,44(5):66-69

针对现有GPS时间序列研究中不同插值方法对比方面研究不足,文中选取ITRF2008框架下的7个IGS基准站坐标时间序列,按照其缺值情况分为6种方案,分别采用线性插值、三次样条插值、拉格朗日插值和建模插值等6种方法对不同缺值情况下的GPS时间序列进行插值,并对不同方法的插值效果进行对比分析．结果表明，三次样条插值和拉格朗日插值效果较差;当缺值数量较少时,最邻近插值、线性插值、三次多项式插值和建模插值效果相差不大;随着缺值数量的增加,建模插值效果最好．   相似文献   

珠江三角洲沉积体与河网干流河道的形成发育   总被引：3，自引：1，他引：2  

韦惺  吴超羽 《海洋学报》2018,40(7):66-78

应用PRD-LTMM长周期"动力-沉积-形态"模型和非线性动力学拉格朗日拟序结构理论对全新世海侵盛期以来珠江三角洲以及河网干道的形成演变进行了地貌动力学分析，结果显示:受曲折岸线和复杂地形的影响，海侵盛期古珠江河口湾的水动力随时空高度变化，形成了7个具有不同运动特性的条带区域，并产生了许多不同尺度且相对独立的沉积动力结构，形成了众多的沉积体。这些沉积体成为了三角洲发育演变的基本建构单元。三角洲的主体沉积可概括为受原始地形分隔的若干相对独立的充填过程，干流河道的形成和发育往往是若干相邻沉积体发育和延伸的结果，而三角洲河网干道的总体分布格局则受这些动力区域所控制。  相似文献   

A generalized frontogenesis function and its application   总被引：3，自引：0，他引：3  

Shuai Yang  Shouting Gao  Chungu Lu 《大气科学进展》2014,31(5):1065-1078

With the definition of generalized potential temperature, a new generalized frontogenesis function, which is expressed as the Lagrangian change rate of the magnitude of the horizontal generalized potential temperature gradient, is derived. Such a frontogenesis function is more appropriate for a real moist atmosphere because it can reflect frontogenesis processes, in which the atmosphere in a frontal zone is typically characterized by neither completely dry nor uniform saturation. Furthermore, by derivation, the expression of generalized frontogenesis function includes both temperature and humidity gradients, which is different from and superior to the traditional frontogenesis function in moist processes, which also uses equivalent potential temperature. Diagnostic studies of real cases are performed and show that the generalized frontogenesis function in non- uniformly saturated moist atmosphere indeed provides a useful tool for frontogenesis, compared to using the traditional frontogenesis function. The new frontogenesis function can be used in situations involving either a strong temperature or moisture gradient and is closely correlated with precipitation.  相似文献   

基于卫星高度计数据的南海水平搅拌分析          下载免费PDF全文

李玮洁  詹海刚 《热带海洋学报》2014,33(2):10-16

搅拌是海水混合的重要组成,其强度可由基于拉格朗日观点的有限时间李亚普诺夫指数(Finite Time Lyapunov Exponents,FTLE)定量计算。文章利用卫星高度计资料统计分析了2002~2011年间南海地转流场的FTLE时空变化特征。结果显示,FTLE在越南东南海域强度最大,对应水平搅拌作用最强;而在南海西北、东南区域其值偏低。近10年的南海水平搅拌呈缓慢增强趋势,且存在明显的季节变化,夏季较强而冬季偏弱。FTLE的空间分布与基于欧拉观点的涡动能和应变速率相似,强搅拌的区域,其涡动能和应变速率亦较高。与Okubo-Weiss参数的比较则显示,构成流场拉格朗日拟序结构(Lagrangian Coherent Structures,LCS)的FTLE脊线与流场中涡旋联系紧密,FTLE低值集中在旋转主导的涡旋内部,而高值多在涡旋周围应变主导区域。  相似文献   

An improved optimal elemental method for updating finite element models     

段忠东  Spencer B.F  闫桂荣  欧进萍 《地震工程与工程振动(英文版)》2004,3(1):67-74

The optimal matrix method and optimal elemental method used to update finite element models may not provide accurate results. This situation occurs when the test modal model is incomplete, as is often the case in practice. An improved optimal elemental method is presented that defines a new objective function, and as a byproduct, circumvents the need for mass normalized modal shapes, which are also not readily available in practice. To solve the group of nonlinear equations created by the improved optimal method, the Lagrange multiplier method and Matlab function fmincon are employed. To deal with actual complex structures, the float-encoding genetic algorithm (FGA) is introduced to enhance the capability of the improved method. Two examples, a 7degree of freedom (DOF) mass-spring system and a 53-DOF planar frame, respectively, are updated using the improved method.The example results demonstrate the advantages of the improved method over existing optimal methods, and show that the genetic algorithm is an effective way to update the models used for actual complex structures.  相似文献   

拉格朗日点上的天文探测     

徐永煊 《天文爱好者》2009,(9):74-77

拉格朗日点是以著名的法国科学家拉格朗日的名字命名的空间中的几个点,也被称为太空中的天平点。它存在于两个大的天体之间,由于受到两个天体的重力影响,位于这一点上的小型物体可以相对保持平衡,不需要动力推进以抵挡引力作用。在每两个大型的天体之间,比如太阳和木星、地球和月球之间．理论上都存在5个拉格朗日点,利用拉格朗日点的原理,科学家们就有可能制造出不需要能源动力的太空船和空间天文观测台。  相似文献   

重力卫星加速度数据的插值算法研究     

崔立鲁 《测绘工程》2012,21(3):21-25,30

阐述拉格朗日插值法和牛顿插值法的原理,详细地推导其一次、二次微分通用公式,并分别利用推导出来的微分公式对卫星星历模拟数据进行了相应的插值计算,得到对应的卫星加速度数据。通过比较不同公式的计算结果,验证一次、二次微分公式的正确性,并得到一些有益的结论。  相似文献   

A Three-Dimensional Nearshore Hydrodynamic Model with Depth-Dependent Radiation Stresses   总被引：2，自引：0，他引：2  

吴相忠  张庆河 《中国海洋工程》2009,23(2):291-302

For the simulation of the three-dimensional (3D) nearshore circulation,a 3D hydrodynamic model is developed by taking into account the depth-dependent radiation stresses.Expressions for depth-depeedent radiation stresses in the Cartsian coordinates are introduced on the basis of the linear wave theory,and then vertical variations of depth-dependent radiation stresses are discussed.The 3D hydrodynamic model of EICIRC (Eulerian-Lagrangian CIRCulation) is extended by adding the terms of the depth-dependent or depth-averaged radiation stresses in the momentum equations.The wave set-up,set-down and undertow are simulated by the extended ELCIRC model based on the wave fields provided by the experiment or the REF/DIF wave model.The simulated results with the depth-dependent and depth-averaged radiation stresses both show good agreement with the experimental data for wave set-up and set-down.The undertow profiles predicted by the model with the depth-dependent radiation stresses are also consistent with the experimental results,while the model with the depth-averaged radiation stresses can not reflect the vertical distribution of undertow.  相似文献   

A Lagrangian mean theory on coastal sea circulation with inter-tidal transports I. Fundamentals   总被引：3，自引：1，他引：2  

FENG Shizuo  JU Lian  JIANG Wensheng 《海洋学报(英文版)》2008,27(6):1-16

A brief review is made on the theory of the Lagrangian residual circulation and inter-tidal transports in a convectively weakly nonlinear system. In the review the emphasis is put on the systematical development of the theory and its weakness of convectively weakly nonlinear approximation. The fundamentals of a Lagrangian tidally-averaged theory on circulation with inter-tidal transport processes have been proposed for a general nonlinear coastal/estuarine system. The Lagrangian residual velocity is strictly de- fined, and it has been verified to be able to embody the velocity field of circulation. A new concept of the concentration for inter- tidal transport processes is presented. The concentration describing the inter-tidal transport processes should be a ＂Lagrangian inter-tidal concentration＂ defined and named, but not the Eulcrian tidally-averaged concentration used traditionally. The circulation described here contains a set of infinite temporal-spatial fields of velocity/concentration, each of which corresponds to a specific value of tidal phases varying continuously over one tidal cycle. When the convectively weakly nonlinear condition（ with a smaller order of eddy diffusion and sources） is approximately satisfied, a set of infinite temporal-spatial fields of velocity/concentration can be reduced to a single one.. the mass transport velocity/the Eulerian tidally averaged concentration as exhibited traditionally.  相似文献