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1.
由于在数据同化过程中远距离的观测与同化状态之间存在着虚假相关,局地化方法受到广泛关注。同时,在集合数目较少的同化情况下,观测数据难以得到有效利用,使得同化效果欠佳。因此,提出了一种新的模糊控制局地化同化方法,通过模糊控制算法判断观测点与状态更新点之间的距离,构造观测位置模糊权重。利用非线性Lorenz-96模型,比较分析模糊控制局地化同化(FLETKF)算法与模糊控制同化(FETKF)方法、局地化分析同化(LETKF)算法和集合转换卡尔曼滤波(ETKF)算法在非线性强迫参数变化时的性能,同时探讨了4种算法在不同强度下的优劣。研究结果表明,新方法能够获得更有效的观测权重,避免了远距离观测与状态变量之间的虚假相关,减小由于观测数据难以得到有效利用而带来的误差,在不同观测误差协方差情况下,随着集合数的增加,4种算法中FLETKF能够保持较好的鲁棒性,在观测误差协方差较大时,FLETKF方法的均方根误差(RMSE)相对FETKF方法的RMSE值减小98.2%,提高了同化精度,但在同化所需时间上,由于模糊控制局地化同化方法在判断观测点与状态更新点之间的距离,构造观测位置等价权重需要较长的额外时间,因此,并行计算的性能需进一步研究。 相似文献
2.
《地球科学进展》2017,(4)
基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所(IAP)近期气候预测系统(以下简称IAP Dec Pre S系统)发展了2种初始化方法:第一种采用Incremental Analysis Update(IAU)方案同化格点化的海洋温度和盐度客观分析资料EN3;第二种采用集合最优差值(EnOI)结合IAU(EnOI-IAU)的方案同化原始海洋温度和盐度观测廓线资料EN4。主要目的是比较基于2种初始化方案开展的年代际预测试验的技巧。时间相关系数、均方根技巧评分等指标均表明,基于EnOI-IAU方案的回报试验对与太平洋年代际振荡(PDO)有关的北太平洋海表面温度(SST)的回报技巧显著高于基于IAU方案的回报试验。而对于大西洋多年代际振荡(AMO),EnOI-IAU方案回报试验的技巧低于IAU方案回报试验。AMO存在副极地和热带北大西洋2个活动中心,EnOIIAU方案在热带中心的技巧仅略低于IAU方案,但是它在热带外区域模拟出了虚假的降温趋势,因此技巧远低于后者。 相似文献
3.
利用1998年7月6日至8月9日青藏高原GAME-Tibet试验区MS3608站点的4cm、20cm和100cm的土壤水分观测数据同化SiB2模型输出的表层、根区和深层土壤水分,探讨了一个基于集合卡尔曼滤波和简单生物圈模型的单点土壤水分同化方案。分析和评价了集合大小、同化周期、模型误差、背景场误差以及观测误差对同化系统性能的影响。结果表明:①增加集合数目可以减小土壤水分同化系统的误差,但同时又降低了运行效率;②对于集合卡尔曼滤波,初始场的估计是否准确对同化系统性能影响不大;③模型误差和观测误差的准确估计可以提高土壤水分的估计精度;④利用数据同化的方法对土壤水分的估计有显著提高。 相似文献
4.
EnKF同化的背景误差协方差矩阵局地化对比研究 总被引：1，自引：1，他引：0
在集合数据同化中,背景场误差的协方差估计特别重要。通常有限个成员的集合在估计背景误差协方差矩阵时会引入伪相关,从而造成协方差被低估、滤波发散。虽然协方差膨胀的经验性方法能一定程度缓解协方差被低估的问题,但不能消除协方差的伪相关问题。因此,结合EnKF方案探讨2种消除伪相关的局地化方法(协方差局地化方法和局地分析方法),分析这2种局地化方法对背景误差协方差矩阵、增益矩阵、集合转换矩阵以及同化结果的影响。实验结果表明:局地化方法不仅能消除背景误差协方差矩阵的伪相关,还可以增加背景误差协方差矩阵的秩;在"弱"同化强度下,2种局地化方法的增益矩阵和集合转换矩阵相等;随着同化强度的增大,增益矩阵和集合转换矩阵的差异会变大;在不同的同化强度下,2种局地化方法各具特色,相对而言,协方差局地化方法在更新集合均值和集合扰动上具有较强的鲁棒性。研究结论有助于背景场误差协方差的精细分析和估计。 相似文献
5.
为研究观测资料稀少情况下土壤质地及有机质对土壤水分同化的影响,发展了集合卡尔曼平滑(Ensemble Kalman Smooth, EnKS)的土壤水分同化方案。利用黑河上游阿柔冻融观测站2008年6月1日至10月29日的观测数据,使用EnKS算法将表层土壤水分观测数据同化到简单生物圈模型(Simple Biosphere Model 2, SiB2)中,分析不同方案对土壤水分估计的影响,并与集合卡尔曼滤波算法(EnKF)的结果进行比较。研究结果表明,土壤质地和有机质对表层土壤水分模拟结果影响最大而对深层的影响相对较小;利用EnKF和EnKS算法同化表层土壤水分观测数据,均能够显著提高表层和根区土壤水分估计的精度,EnKS算法的精度略高于EnKF且所受土壤质地和有机质的影响小于EnKF;当观测数据稀少时,EnKS算法仍然可以得到较高精度的土壤水分估计。 相似文献
6.
河流生态修复模拟评估过程中修复情景的大批量产生特性以及模拟计算结果的高精度要求,使得海量情景的模拟计算工作量巨大。为提高情景模拟计算速度和缩短决策时间,将并行计算技术引入河流生态修复模拟评估过程,设计了基于MPI的并行计算算法,实现了模拟计算的并行化处理。算法包括读取决策变量取值集合和约束条件集合、决策变量取值集合分解、情景生成、情景模拟、模拟结果写入文件等主要步骤,其中设计了自适应集合分解子算法,用以解决并行处理中的负载均衡问题。以永定河生态修复为例,在单机多核计算机平台上应用算法进行了对比实验,在4核平台上使模拟计算时间减少为串行时的近四分之一,加速比达3.8,在万级、十万级和百万级情景数量规模下均保持稳定一致的加速比。实验结果表明:该算法性能稳定,实用性强,可有效缩短海量情景模拟的计算时间,显著提高计算效率。 相似文献
7.
在集合数据同化过程中,由于远距离的观测与同化状态之间存在着虚假相关,局地化方法受到广泛关注.此外,由于集合数的限制,容易引起欠采样和协方差被低估等现象,使得滤波效果欠佳.因此,提出模糊控制算法,模糊控制算法主要用于判断观测点与状态更新点之间的距离来匹配相应的观测权重,进而调整局地化系数来更新背景误差协方差和观测误差协方差矩阵,从而得到有效的状态估计.基于背景误差协方差局地化方法和观测误差协方差局地化方法,耦合模糊控制,形成了新的算法—模糊控制的背景误差协方差局地化方法和模糊控制的观测误差协方差局地化方法.利用Lorenz-96模型,在小集合数和局地化半径下,得出模糊控制的背景误差协方差局地化方法和模糊控制的观测误差协方差局地化方法有较好的同化性能.通过分析泰勒图谱甄别出新算法与观测点具有高度的相关性以及较小的空间变异性.最后,在不同维数的模糊控制器下,新算法的有效性进一步得到验证.为今后数据同化误差处理方面提供了良好的研究平台. 相似文献
8.
9.
数据同化算法研究现状综述 总被引：13，自引：2，他引：11
近年来,全球环境变化对人类生存影响日益突出,为了加强对陆地—大气—海洋的监测,全球对地观测系统计划(GEOSS)和全球环境与安全监测计划(GMES)等相继被提出。数据同化算法作为连接观测数据与模型模拟预测的关键桥梁也得到了迅速发展,显著标志新的数学研究成果不断被引入数据同化算法中。在国家重大科技基础设施项目"航空遥感系统——地球科学数据处理软件系统"需求背景条件下,梳理遥感数据同化算法的国内外发展现状,明确数据同化算法开发的技术主线和重点内容,稳步推进数据同化算法理论研究和软件开发。 相似文献
10.
全球海洋再分析产品的研究现状 总被引：4，自引：3，他引：1
随着海洋观测资料的积累和日益丰富,以及海洋数值模式与数据同化方法的不断发展,利用同化系统将海洋数值模式和历史观测资料结合起来,对重构海洋过去的演变以形成再分析资料的作用和意义越来越显著。再分析产品为人们深入了解多时空尺度的海洋运动和探究海洋在气候变化中的作用提供了不可替代的资料基础。受海洋模式与数据同化方法的发展水平和庞大的计算资源需求等方面的限制,全球海洋再分析产品主要由海洋科技强国制作与发布。就当前国内外一些主要的全球海洋再分析计划及其产品进行分析,对各产品的特点及应用中存在的一些问题进行介绍,最后对全球海洋再分析产品未来的发展趋势进行了展望和讨论。 相似文献
11.
An integrated analysis about computational time complexity of the Local Ensemble Transform Kalman Filter (LETKF) was performed. It is found that the calculation step of inverse matrix of the error covariance in ensemble space is the most computationally intensive and time consuming. In a parallel computing environment, the uneven distribution of CPU calculations in this step directly leads to low computational efficiency. To solve this problem, a new load balancing strategy was designed based on the "greedy algorithm". A high-performance parallel ocean data assimilation system based on the LETKF was developed and tested using this strategy. This system was based on the Parallel Ocean Program 2 (POP2) of the Community Earth System Model (CESM). The optimal interpolated sea surface temperature data (OISST) and Argo temperature profile data from January to February, 2004 were assimilated into the POP2. The results show that data assimilation effectively reduces the root mean square error of temperature and salinity. Using the new strategy, the exact same results are obtained but the computation time is reduced by half. At higher resolution (0.1°×0.1°),the computing performance is still doubled, indicating that this load balancing scheme is stable and reliable. In addition, the new method has high scalability and portability with great potential to be applied in operational forecasting. 相似文献
12.
Due to the fake correlation between distance-observations and assimilation-states during data assimilation, more attention has been paid to the localization method. Meanwhile, in the case of assimilation with a small number of sets, the observation data is difficult to be used effectively, which makes the assimilation effect not good enough. Therefore, a new fuzzy control was proposed to analyze the local method. The fuzzy control algorithm was used to judge the distance between the observation point and the status update point and to construct the fuzzy weight of the observation position. The study aimed to make use of the nonlinear Lorenz-96 model to compare the Fuzzy control combine Local Analysis algorithm (FLETKF) and Fuzzy control combine Ensemble Transform Kalman Filter method (FETKF), local Ensemble Transform Kalman Fliter (LETKF) and Ensemble Transform Kalman Filter algorithm (ETKF) when the nonlinear forced parameter changed. In addition, the strengths and weaknesses of four algorithms were discussed by different intensities. The results show that the new method can obtain more effective observation weights, avoiding the false correlation between long-distance observations and state variables, reducing the errors caused by the observation data which is difficult to be used effectively. Under different assimilation strength, FLETKF can maintain good robustness. However, in terms of assimilation time, the construction of the equivalent weight of the observation position requires additional time because the localization assimilation method of fuzzy control determines the distance between the observation point and the status update point. Parallel computing performance needs further study. 相似文献
13.
基于PC机群波动方程叠前深度偏移的并行计算策略 总被引：2，自引：0，他引：2
基于波动方程的叠前深度偏移技术是解决复杂地质地貌地区地震成像的一种非常有效的手段,但是在实际应用中面临着数据量巨大和计算量巨大的双重困难.以PC 机集群为硬件环境,以MPI消息传递并行编程环境为并行程序设计平台,研究设计出请求分配作业的主从模式来实现波动方程叠前深度偏移的并行计算,从而解决了动态负载均衡难题,采用的作业登记与分析技术解决了容错处理问题.理论模型数据和实际地震资料测试结果表明:程序运行稳定,并行效率高.对我国东部地区某三维地震数据进行了处理,用请求分配作业的主从模式比平均分配作业的主从模式节省了23.68%的时间. 相似文献
14.
Edison Caballero Fernando A. Rochinha Marcio Borges Marcio A. Murad 《国际地质力学数值与分析法杂志》2019,43(2):482-500
In this work, we construct a new methodology for enhancing the predictive accuracy of sequential methods for coupling flow and geomechanics while preserving low computational cost. The new computational approach is developed within the framework of the fixed-stress split algorithm procedure in conjunction with data assimilation based on the ensemble Kalman filter (EnKF). In this context, we identify the high-fidelity model with the two-way formulation where additional source term appears in the flow equation containing the time derivative of total mean stress. The iterative scheme is then interlaced with data assimilation steps, which also incorporate the modeling error inherent to the EnKF framework. Such a procedure gives rise to an “enhanced one-way formulation,” exhibiting substantial improvement in accuracy compared with the classical one-way method. The governing equations are discretized by mixed finite elements, and numerical simulation of a 2D slab problem between injection and production wells illustrate the tremendous achievement of the method proposed herein. 相似文献
15.
The material point method (MPM), which is a combination of the finite element and meshfree methods, suffers from significant computational workload due to the fine mesh that is required in spite of its advantages in simulating large deformations. This paper presents a parallel computing strategy for the MPM on the graphics processing unit (GPU) to boost the method’s computational efficiency. The interaction between a structural element and soil is investigated to validate the applicability of the parallelisation strategy. Two techniques are developed to parallelise the interpolation from soil particles to nodes to avoid a data race; the technique that is based on workload parallelisation across threads over the nodes has a higher computational efficiency. Benchmark problems of surface footing penetration and a submarine landslide are analysed to quantify the speedup of GPU parallel computing over sequential simulations on the central processing unit. The maximum speedup with the GPU used is ∼30 for single-precision calculations and decreases to ∼20 for double-precision calculations. 相似文献
16.
非连续变形分析（DDA）方法严格满足平衡要求和能量守恒,具有完全的运动学及数值可靠性,但对大规模岩土工程问题的数值模拟耗时太长,尤其是线性方程组求解,并行计算可以很好地解决该问题。首先基于DDA方法的基本理论,阐述了适用于DDA方法中的基于块的行压缩法和基于“试验-误差”迭代格式的非零位置记录;其次,引入块雅可比迭代法并行求解DDA方法的线性方程组,并改进了相应的非零存储方法;最后,基于OpenMP实现了DDA线性方程组求解并行计算,并将其应用于地下洞室群的破坏过程分析,以加速比为并行效率的指标评价,结果表明,该并行计算策略可以极大提高DDA的计算效率,而且适合各种规模的问题。 相似文献
17.
This paper focuses on the efficiency of finite discrete element method (FDEM) algorithmic procedures in massive computers and analyzes the time-consuming part of contact detection and interaction computations in the numerical solution. A detailed operable GPU parallel procedure was designed for the element node force calculation, contact detection, and contact interaction with thread allocation and data access based on the CUDA computing. The emphasis is on the parallel optimization of time-consuming contact detection based on load balance and GPU architecture. A CUDA FDEM parallel program was developed with the overall speedup ratio over 53 times after the fracture from the efficiency and fidelity performance test of models of in situ stress, UCS, and BD simulations in Intel i7-7700K CPU and the NVIDIA TITAN Z GPU. The CUDA FDEM parallel computing improves the computational efficiency significantly compared with the CPU-based ones with the same reliability, providing conditions for achieving larger-scale simulations of fracture. 相似文献
18.
The efficiency of current adjoint-based observations targeting strategies in variational data assimilation is closely determined
by the underlying assumption of a linear propagation of initial condition errors into the model forecasts. A novel targeting
strategy is proposed in the context of four-dimensional variational data assimilation (4D-Var) to account for nonlinear error
growth as the forecast lead time increases. A quadratic error growth model is shown to maintain the accuracy in tracking the
nonlinear evolution of initial condition perturbations, as compared to the first-order approximation. A second-order adjoint
model is used to provide the derivative information that is necessary in the higher-order Taylor series approximation. The
observation targeting approach relies on the dominant eigenvectors of the Hessian matrix associated with a specific forecast
error aspect as an indicator of the directions of largest quadratic error growth. A comparative qualitative analysis between
observation targeting based on first- and second-order adjoint information is presented in idealized 4D-Var experiments with
a two-dimensional global shallow-water model. The results indicate that accounting for the quadratic error growth in the targeting
strategy is of particular benefit as the forecast lead time increases. 相似文献
19.
为了提高分布式环境下海量空间数据的空间运算的效率,解决空间分析处理模块在设计上与底层的数据库服务协议、空间数据模型等透明一致的设计问题.分析了分布式空间运算具备的基本特征,从空间运算任务分解和分布式空间数据的划分方法、共享数据复制策略、基于负载的数据划分策略和空间运算框架的缓存机制等几个方面讨论分布式空间信息的运算技术体系,并提出现阶段可行的实现框架.基于本框架开发的系统用于实际应用中,较好地解决了分布式环境下的大规模复杂空间数据运算的效率问题.以分布式环境下的经典空间运算为例进行的试验表明:该框架设计新颖,提高了空间运算效率. 相似文献
20.
Dave R. Stegman Louis Moresi Robert Turnbull Julian Giordani Patrick Sunter Alan Lo Steve Quenette 《Visual Geosciences》2008,13(1):71-84
High-performance computing provides unprecedented capabilities to produce higher resolution 4-D models in a fraction of time.
Thus, the need exists for a new generation of visualization systems able to maintain parity with the enormous volume of data
generated. In attempting to write this much data to disk, each computational step introduces a significant performance bottleneck,
yet most existing visualization software packages inherently rely on reading data in from a dump file. Available packages
make this assumption of postprocessing at quite a fundamental level and are not very well suited for plotting very large numbers
of specialized particles. This necessitates the creation of a new visualization system that meets the needs of large-scale
geodynamic modeling. We have developed such a system, gLucifer, using a software framework approach that allows efficient
reuse of our efforts in other areas of research. gLucifer is capable of producing movies of a 4-D data set “on the fly” (simultaneously
with running the parallel scientific application) without creating a performance bottleneck. By eliminating most of the human
efforts involved in visualizing results through postprocessing, gLucifer reconnects the scientist to the numerical experiment
as it unfolds. Data sets that were previously very difficult to even manage may be efficiently explored and interrogated without
writing to disk, and because this approach is based entirely on memory distributed across as many processors as are being
utilized by the scientific application, the visualization solution is scalable into terabytes of data being rendered in real
time. 相似文献