共查询到19条相似文献，搜索用时 109 毫秒
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卫星遥感获取的海冰密集度观测资料中包含着空间多尺度信息。然而，多数传统的数据同化方法难以在海冰密集度变化较为复杂的海冰边缘区有效提取这些多尺度信息。为解决上述问题，本文设计了一种基于变分优化的逐步订正分析方法—空间多尺度递归滤波，该方法是逐步订正分析与最小化算法的结合，它能够从长波到短波依次提取观测中的各种空间尺度信息。与传统的客观分析相比，这种基于变分的多尺度分析方法不仅能够在最小化过程中一次性的提取出观测中的多尺度信息，而且能够方便合理的进行参数配置。单观测点同化试验的分析结果表明，空间多尺度递归滤波方法具有良好的观测信息空间传播能力。随后在二维海冰密集度的分析试验中，该方法能够较好的提取SSMI海冰密集度观测资料中的空间多尺度信息，进而获得高精度的海冰密集度分析结果。 相似文献
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为了提升磁梯度数据相关成像法对不同深度的多磁性目标的成像效果，提出了一种自适应滤波方法。首先将待成像空间划分为三维规则网格，通过解析法计算位于不同网格的磁性体在观测平面的理论磁梯度，然后依据各磁性体的磁梯度数据频谱特征来决定观测数据的滤波阈值，最后将滤波后的观测数据用于相关成像。仿真模型实验表明：对于位置较浅磁性体，根据成像结果估计的磁性体中心位置与实际基本相符， 滤波处理最多减小了约 76%的误差，对于平均 1.7 m 深的多个磁性体，估计的中心位置最大误差 0.3 m，相比于无滤波处理的结果误差减小了 46%左右，信噪比不足时，对近似球体的模型仍然有较好的定位效果。说明自适应滤波在一定程度上能改善三维相关成像的分辨率，提升水下磁性目标定位的准确度。 相似文献
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针对多尺度带乘性噪声系统,在多尺度最优滤波融合的基础上,进行状态最优固定域平滑算法的研究.通过推广得到的平滑算法需要大量的局部传感器参数,而分布式多尺度滤波融合后不能保留这些信息.针对这一弊端对算法进行改进,推导出仅使用融合后的一步预测及滤波值的平滑算法.该算法在线性最小方差意义下是最优的.计算机仿真验证了算法的可行性. 相似文献
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利用小波变换和多尺度分析的思想，将基于模型的动态系统分析和基于统计特性的多尺度信号变换方法相结合。提出了在线性最小方差意义下的带乘性噪声系统的多尺度最优滤波融合算法。并用计算机仿真说明了融合算法的有效性。 相似文献
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在隧道、城市峡谷、多径效应明显等恶劣环境中,GNSS定位结果易受异常值影响。GNSS异常值的存在使得观测噪声服从Gauss分布的假设不再成立,从而将严重影响GNSS/INS组合系统中Kalman滤波的性能。本文将抗差Kalman滤波用于GNSS/INS组合导航系统中异常观测的探测与抑制。根据设定的显著性水平对Kalman滤波的新息向量进行c2检验,原假设被拒绝时认为异常观测存在;然后引入尺度化因子对新息向量的协方差矩阵进行膨胀,以抑制异常观测对滤波结果的影响,并通过解析方法求解该因子。数值仿真的结果验证了算法的有效性。 相似文献
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针对水下图像对比度偏低，细节模糊的问题，本文提出基于非锐化掩模引导滤波的细节增强方法。首先由原始图像做引导图进行滤波得到细节层图像，并对细节层使用噪声检测的中值滤波去除斑点噪声；然后对原始图像进行基于均值滤波的非锐化掩模，得到锐化图像，并将锐化图像作为引导图对原始图像进行引导滤波，获取基础层图像；最后将滤波后的细节层进行增益后与引导滤波获取的基础层进行叠加，达到增强水下图像细节的目的。并通过信息熵、局部对比度和平均梯度3种客观评价指标对图像处理结果进行了对比分析，主观和客观测试结果表明，本文采用的算法能够有效提高图像对比度以及增强细节信息，有利于提高水下图像资料解释的准确性。 相似文献
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遥感影像中海洋锋具有弱边缘(Weak Edge)信息特性,其空间尺度在不同的空间位置存在较大的差异。针对传统边缘算子只能提取某一尺度的海洋锋信息,而损失其他尺度信息不足,本文利用小波多尺度分析特性,探讨了海洋锋信息在各尺度间的分布的继承性,提出最佳尺度确定的算法框架,设计出最佳尺度确定算法的流程,进一步进行海洋锋各尺度信息的提取。最后以海面温度锋-墨西哥湾流为实例进行形态特征提取,并与典型的边缘提取算子效果在信息量、抗干扰性、定位精度、连续性和对比度上进行对比分析。试验结果表明了该算法在提取多尺度的海洋锋信息上的可行性和实用性。 相似文献
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Four-dimensional variational(4D-VAR) data assimilation method is a perfect data assimilation solution in theory, but the compu- tational issue is quite difficult in operational implementation. The incremental 4D-VAR assimilation scheme is set up in order to re- duce the computational cost. It is shown that the accuracy of the observations, the length of the assimilation window and the choice of the first guess have an important influence on the assimilation outcome through the contrast experiment. Compared with the standard 4D-VAR assimilation scheme, the incremental 4D-VAR assimilation scheme shows its advantage in the computation speed through an assimilation experiment. 相似文献
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With the development and deployment of observation systems in the ocean, more precise passive and active microwave data are becoming available for the weather forecasting and the climate monitoring. Due to the complicated variability of the sea ice concentration(SIC) in the marginal ice zone and the scarcity of high-precision sea ice data, how to use less data to accurately reconstruct the sea ice field has become an urgent problem to be solved. A reconstruction method for gridding observations ... 相似文献
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应用 Prandtl混合长理论导得既包含梯度项又包含二阶导数的湍流通量闭合方案 ,并进一步分析了该封闭方案用于湍流扩散方程的数值解行为。分析表明 :(1)扩散项使污染物扩散并趋于空间均匀分布 ,而频散项导致污染物空间分布非均匀 ;(2 )所给出的改进后的一阶湍流封闭方案既可解释标量物质的局地反梯度输送现象又可能使 K理论用于混合层。 相似文献
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In order to better estimate meso-scale variabilities in the energetic Kuroshio Extension (KE) region, simultaneous assimilation of drifter-derived velocity data, together with satellite and in situ hydrographic data, is attempted by using a high-resolution 4-dimensional variational data assimilation (4D-VAR) system. Our experimental results, both with and without assimilation of drifter data (Exp. Drf and Exp. Ref, respectively) for the period during Aug–Oct 2005, show that the reproduced fields in Exp. Drf better reflect the observed meso-scale features such as the KE meandering jet and associated eddies. The adjoint sensitivity analysis indicates that our 4D-VAR system has the ability to provide a more realistic timeseries of the meandering jet structures that play a key role in the intergyre exchange between the subtropical and subarctic gyres in the North Pacific. In addition, the observed information from the surface drifters works to improve the subsurface structure. These results illustrate the advantage of our 4D-VAR simultaneous assimilation with the addition of drifter-derived surface velocity information. 相似文献
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Zeng’an Deng Jiye Jin Fengying Ji Feng Zhang Xiaoyi Jiang Wei Wang 《Marine Geodesy》2013,36(1):109-122
Tracer diffusion is an important issue in ocean modeling, and isoneutral slope is key to parameterization of tracer diffusion in the ocean interior when using the isoneutral/dianeutral scheme. In this study, multiyear mean temperature, salinity, and pressure-gridded products that cover the upper 2000 m of the global ocean are created by employing all the Argo float observations up to date. Comparison with WOA09 data indicates that Argo temperature and salinity depict the reality well. Based on the reliable Argo gridded products, the in situ density fields are calculated. Then isoneutral slope in the ocean interior deep to 2000 m was determined by using the Argo-derived density. Taking advantage of isoneutral slope, therefore, diffusion tensor as well as isoneutral tracer diffusion flux can be obtained in combination of the tracer diffusion coefficient. The aim of this work is to propose a procedure to estimate the isoneutral slope using Argo observations and to offer new isoneutral slope-gridded products in the hope of further facilitating the parameterization of isoneutral tracer diffusion in geopotential (Z-coordinate) ocean models. 相似文献
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水下溢油数值模拟研究 总被引：1，自引：0，他引：1
基于Lagrange积分法和Lagrange粒子追踪法建立了一个水下溢油数值模型。该溢油模型由两个子模型组成:羽流动力模型和对流扩散模型,其中羽流动力模型用以模拟溢油的喷发阶段和浮力羽流阶段;对流扩散模型用以模拟溢油的对流扩散阶段。通过数值实验,结合实验室水槽实验和水下溢油现场实验的观测资料进行模型验证。实验结果表明,模拟结果与观测资料一致性较好,从而验证了本文溢油模型的合理性和准确性;羽流动力模型为对流扩散模型提供源,海流、海水的垂向密度结构和油滴的直径分布是影响溢油在对流扩散阶段运动和分布的主要因素。 相似文献
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根据Ｔａｙｌｏｒ的湍流扩散理论和Ｈａｙ、Ｐａｓｑｕｉｌｌ提出的拉格朗日流和欧拉流的相关函数的相似性，用黄河三角洲埕北海域的实测资料，按四种不同方案计算出该海域的水平扩散系数和谱密度分布。指出：该海区潮流扩散系数主要受潮流的影响，其分布特征与潮流的分布基本一致，所求的水平扩散系数主要是由周期性的潮运动给予潮流扰动所致。方案４是通过富氏变换滤波消去了周期性潮流扰动，本方案计算的水平扩散系数是由周期为６ｈ以下的小尺度涡提供能量。 相似文献
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A technique for predicting the bubble growth along a two-dimensional hydrofoil with traveling bubble cavitation is presented. The method is based on the dynamic response of ambient microbubbles to the flow field and the subsequent diffusion of dissolved air into the flow field cavities. The bubble growth model is divided into three components, including the prediction of 1) the hydrofoil surface pressure distribution, 2) the ambient microbubble response to the pressure distribution, and 3) the diffusive mass flow rate. The hydrofoil velocity and pressure field is determined by two-dimensional thin airfoil theory. The microbubble response to the pressure field is given by the Rayleigh-Plesset equation with the addition of a mass diffusion term. The diffusion of dissolved gasses into the cavitation bubbles is determined by a solution to the steady-state diffusion equation under spherically symmetric convective flow. Results are given for the bubble wake of a NACA 66-006 (a = 0.8 meanline) hydrofoil with traveling bubble cavitation. The effect of the relative velocity of the cavitation bubbles with respect to the surrounding water is investigated as well as the significance of the mass diffusion term in the Rayleigh-Plesset equation. 相似文献
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Since QuikSCAT is available in cloudy and rainy condition, its wind data are valuable in monitoring and real timeorecasting the wind field, especially in sparse genesis regions of tropical cyclones. In order to understand and investigate the impact of QuikSCAT wind data, the three-dimensional variational data assimilation (3D-VAR) of scatterometric wind data has been employed for the tropical cyclone “Vongfong” in the year 2002. The result shows that the QuikSCAT wind data have positive impact on the analysis and forecasting. But the positive impact is slight. The present results suggest that how to assimilate QuikSCAT wind data effectively is important and will be a challenge to meteorologists. 相似文献