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1.
The simulation of surface flow dynamics using a flow-path network model   总被引：1，自引：0，他引：1  
This paper proposes a flow-path network (FPN) model to simulate complex surface flow based on a drainage-constrained triangulated irregular network (TIN). The TIN was constructed using critical points and drainage lines extracted from a digital terrain surface. Runoff generated on the surface was simplified as ‘water volumes’ at constrained random points that were then used as the starting points of flow paths (i.e. flow source points). The flow-path for each ‘water volume’ was constructed by tracing the direction of flow from the flow source point over the TIN surface to the stream system and then to the outlet of the watershed. The FPN was represented by a set of topologically defined one-dimensional line segments and nodes. Hydrologic variables, such as flow velocity and volume, were computed and integrated into the FPN to support dynamic surface flow simulation. A hypothetical rainfall event simulation on a hilly landscape showed that the FPN model was able to simulate the dynamics of surface flow over time. A real-world catchment test demonstrated that flow rates predicted by the FPN model agreed well with field observations. Overall, the FPN model proposed in this study provides a vector-based modeling framework for simulating surface flow dynamics. Further studies are required to enhance the simulations of individual hydrologic processes such as flow generation and overland and channel flows, which were much simplified in this study.  相似文献   

2.
Cellular automata (CA), which are a kind of bottom-up approaches, can be used to simulate urban dynamics and land use changes effectively. Urban simulation usually involves a large set of GIS data in terms of the extent of the study area and the number of spatial factors. The computation capability becomes a bottleneck of implementing CA for simulating large regions. Parallel computing techniques can be applied to CA for solving this kind of hard computation problem. This paper demonstrates that the performance of large-scale urban simulation can be significantly improved by using parallel computation techniques. The proposed urban CA is implemented in a parallel framework that runs on a cluster of PCs. A large region usually consists of heterogeneous or polarized development patterns. This study proposes a line-scanning method of load balance to reduce waiting time between parallel processors. This proposed method has been tested in a fast-growing region, the Pearl River Delta. The experiments indicate that parallel computation techniques with load balance can significantly improve the applicability of CA for simulating the urban development in this large complex region.  相似文献   

3.
传统分布式水文模型采用串行计算模式,其计算能力无法满足大规模水文精细化、多要素、多过程耦合模拟的需求,亟需并行计算的支持。进入21世纪后,计算机技术的飞速发展和并行环境的逐步完善,为分布式水文模型并行计算提供了软硬件支撑。论文从并行环境、并行算法2个方面对已有研究进行总结概括,分析了不同并行环境和并行算法的优势与不足,并提出提高模型并行效率的手段,即合理分配进程/线程数缩减通信开销,采用混合并行环境增强模型可扩展性,空间或时空离散化提高模型的可并行性及动态分配计算任务、平衡工作负载等。最后,论文对高性能并行分布式模型的未来研究方向进行展望。  相似文献   

4.
基于DEM的分布式水文模型在大尺度流域应用研究   总被引：52，自引：2，他引：52  
本文选取空间大尺度黄河河源区流域为研究对象,利用分布式水文模型进行径流量模拟,采用1976～1985年唐乃亥水文站逐年、月实测径流资料进行参数率定,确定模型的基本参数,得到了较好的模拟效果。模拟结果表明气候变化是引起黄河河源区径流变化的主要原因。在80～90年代的20年间,黄河河源区由气候变化引起径流减少62.11亿m3,占径流变化总量的108.72%,由土地覆被变化引起径流增加5.73亿m3,增加量占径流变化总量的10.03%。  相似文献   

5.
The continually increasing size of geospatial data sets poses a computational challenge when conducting interactive visual analytics using conventional desktop-based visualization tools. In recent decades, improvements in parallel visualization using state-of-the-art computing techniques have significantly enhanced our capacity to analyse massive geospatial data sets. However, only a few strategies have been developed to maximize the utilization of parallel computing resources to support interactive visualization. In particular, an efficient visualization intensity prediction component is lacking from most existing parallel visualization frameworks. In this study, we propose a data-driven view-dependent visualization intensity prediction method, which can dynamically predict the visualization intensity based on the distribution patterns of spatio-temporal data. The predicted results are used to schedule the allocation of visualization tasks. We integrated this strategy with a parallel visualization system deployed in a compute unified device architecture (CUDA)-enabled graphical processing units (GPUs) cloud. To evaluate the flexibility of this strategy, we performed experiments using dust storm data sets produced from a regional climate model. The results of the experiments showed that the proposed method yields stable and accurate prediction results with acceptable computational overheads under different types of interactive visualization operations. The results also showed that our strategy improves the overall visualization efficiency by incorporating intensity-based scheduling.  相似文献   

6.
Mathematical model of porous media dissolution coupled with two-phase flow is proposed. The model is based on the conception of dissolvable porous medium with deformable mass-variable porous skeleton. Model can be used for simulation of coupled chemo- and hydrogeomechanical processes which are difficult to examine experimentally. Acidizing of calcite oil reservoir is used as an example of the process. Water solution of hydrochloric acid and oil are two fluid phases of the model with several components. Dissolvable porous media is treated as deformable mass-variable solid phase. Change in mass of the solid phase is caused by hydrochloric acid dissolving the calcite part of the solid phase. Dissolution is supposed to be congruent; kinetics is governed by the Nernst law. Software for numerical solution of the model is developed. It uses AmgCL parallel library for high-performance computing in order to deal with large algebraic systems on the each time step of calculations. The library uses algebraic multigrid methods for preconditioning and parallel iterative solvers. NVidia CUDA framework is used as a backend to perform GPGPU calculations, because it proved to be faster than OpenCL framework on this problem. Numerical experiments on the basis of data set from real reservoirs are conducted with the developed software. Good correlation between field and calculated data is achieved. Numerical experiments for different configurations of heterogeneous layer are performed. Acidizing of layers with highly permeable conduit and with random distribution of permeability is modeled.  相似文献   

7.
分布式水文模型的并行计算研究进展   总被引：3，自引：1，他引：2  
大流域、高分辨率、多过程耦合的分布式水文模拟计算量巨大,传统串行计算技术不能满足其对计算能力的需求,因此需要借助于并行计算的支持。本文首先从空间、时间和子过程三个角度对分布式水文模型的可并行性进行了分析,指出空间分解的方式是分布式水文模型并行计算的首选方式,并从空间分解的角度对水文子过程计算方法和分布式水文模型进行了分类。然后对分布式水文模型的并行计算研究现状进行了总结。其中,在空间分解方式的并行计算方面,现有研究大多以子流域作为并行计算的基本调度单元;在时间角度的并行计算方面,有学者对时空域双重离散的并行计算方法进行了初步研究。最后,从并行算法设计、流域系统综合模拟的并行计算框架和支持并行计算的高性能数据读写方法3个方面讨论了当前存在的关键问题和未来的发展方向。  相似文献   

8.
无资料区的径流模拟问题是国内外水文研究的难点之一。基于相似流域的参数移植法是常用的解决方法之一,但如何判断相似流域是制约此类方法发展的难点。本文以滇池流域为例,采用自组织映射神经网络(SOM)和层次聚类分析(HCA)联合模式,选取16个流域物理特征为指标进行子流域分类,以确定相似流域。运用无分层的K-means分类的SOM法将整个滇池流域划分为7类具有水文属性的子流域组,分类情景与HCA基本一致,两者实现相互验证。采用HBV水文模型模拟子流域径流过程,并选择部分子流域进行组内参数移植交叉检验。结果显示,HBV模型可较好的模拟滇池流域径流过程;此外,子流域交叉检验结果优良,表明同组内参数可以相互移植。本文不仅为解决滇池流域无资料问题提供了可靠手段,而且由于SOM实现了高维流域特征可视化展示,有助于管理者全面、深入的把握滇池流域水文属性的空间分布特征,为进行水资源管理提供指导。  相似文献   

9.
泥石流沟道汇流对堆积危险范围影响的数值模拟研究   总被引：1，自引：0，他引：1  
叶健  陈锦雄  陈晓清  朱军  徐柱 《地理科学》2016,36(10):1588-1594
利用离散元法和图形处理器（GPU）并行计算手段建立泥石流运动堆积模型,以自然界沟道泥石流汇流后运动堆积特征及危险范围作为模拟参照,利用所构建的泥石流流通槽完成沟道泥石流不同交汇角汇流模拟试验和堆积危险范围预测,实现了泥石流沟道汇流的可视化模拟和数值模拟。试验结果表明,可视化模拟能够模拟出自然界中泥石流自流通区运动汇流后产生堆积的运动特征;数值模拟实现了锐角条件下仅考虑单因素即沟道交汇角对泥石流堆积危险范围影响的模拟试验。此外,利用GPU并行计算的优势可用于模拟大规模泥石流汇流现象,模型的可扩展性为泥石流汇流堆积危险范围分析向更为复杂的地理环境模拟奠定基础。  相似文献   

10.
分布式水文模型软件系统研究综述   总被引：3，自引：1，他引：2  
分布式水文模型软件系统作为分布式水文模型的技术外壳,是模型应用的重要技术保障。当前分布式水文模型应用呈现出多过程综合模拟、用户群范围广和计算量大的特点,对分布式水文模型软件系统的灵活性、易用性和高效性提出了更高的要求。本文首先分析了分布式水文模型应用的主要流程,之后从应用视角对现有分布式水文模型软件系统的特点进行了归纳,主要结论为:①软件系统按照模型结构灵活性的高低分为以下3种类型:不支持子过程选择和算法设置,不支持子过程选择、但支持算法设置,同时支持子过程选择和算法设置;②根据用户操作数据预处理软件方式的不同,参数提取方式分为菜单/命令行式和向导式;③按照模型的程序实现方法分为串行和并行方式,按照模型运行环境分为本地和网络模式。现有软件系统在灵活性、易用性和高效性方面存在如下问题:一是尚未解决模型结构灵活性和对用户知识依赖性之间的矛盾;二是现有菜单/命令行式和向导式的参数提取方式步骤繁琐,难以实现参数的自动提取;三是模型大多为串行方式和本地模式,容易遇到计算瓶颈问题。最后从模块化、智能化、网络化及移动化、并行化和虚拟仿真等方面探讨了分布式水文模型软件系统的发展趋势和研究方向。  相似文献   

11.
We have formulated a 3-D inverse solution for the magnetotelluric (MT) problem using the non-linear conjugate gradient method. Finite difference methods are used to compute predicted data efficiently and objective functional gradients. Only six forward modelling applications per frequency are typically required to produce the model update at each iteration. This efficiency is achieved by incorporating a simple line search procedure that calls for a sufficient reduction in the objective functional, instead of an exact determination of its minimum along a given descent direction. Additional efficiencies in the scheme are sought by incorporating preconditioning to accelerate solution convergence. Even with these efficiencies, the solution's realism and complexity are still limited by the speed and memory of serial processors. To overcome this barrier, the scheme has been implemented on a parallel computing platform where tens to thousands of processors operate on the problem simultaneously. The inversion scheme is tested by inverting data produced with a forward modelling code algorithmically different from that employed in the inversion algorithm. This check provides independent verification of the scheme since the two forward modelling algorithms are prone to different types of numerical error.  相似文献   

12.
Despite its popularity, agent-based modeling is limited by serious barriers that constrain its usefulness as an exploratory tool. In particular, there is a paucity of systematic approaches for extracting coarse-grained, system-level information as it emerges in direct simulation. This is particularly problematic for agent-based models (ABMs) of complex urban systems in which macroscopic phenomena, such as sprawl, may manifest themselves coarsely from bottom-up dynamics among diverse agent-actors interacting across scales. Often these connections are not known, but treating them is nevertheless crucial in enabling prediction, in supporting decisions, and in facilitating the design, control, and optimization of urban systems. In this article, we describe and implement a metasimulation scheme for extracting macroscopic information from local dynamics of agent-based simulation, which allows acceleration of coarse-scale computing and which may also serve as a precursor to handle emergence in complex urban simulation. We compare direct ABM simulation, population-level equation solutions, and coarse projective integration. We apply the scheme to the simulation of urban sprawl from local drivers of urbanization, urban growth, and population dynamics. Numerical examples of the three approaches are provided to compare their accuracy and efficiency. We find that our metasimulation scheme can significantly accelerate complex urban simulations while maintaining faithful representation of the original model.  相似文献   

13.
A general-purpose parallel raster processing programming library (pRPL) was developed and applied to speed up a commonly used cellular automaton model with known tractability limitations. The library is suitable for use by geographic information scientists with basic programming skills, but who lack knowledge and experience of parallel computing and programming. pRPL is a general-purpose programming library that provides generic support for raster processing, including local-scope, neighborhood-scope, regional-scope, and global-scope algorithms as long as they are parallelizable. The library also supports multilayer algorithms. Besides the standard data domain decomposition methods, pRPL provides a spatially adaptive quad-tree-based decomposition to produce more evenly distributed workloads among processors. Data parallelism and task parallelism are supported, with both static and dynamic load-balancing. By grouping processors, pRPL also supports data–task hybrid parallelism, i.e., data parallelism within a processor group and task parallelism among processor groups. pSLEUTH, a parallel version of a well-known cellular automata model for simulating urban land-use change (SLEUTH), was developed to demonstrate full utilization of the advanced features of pRPL. Experiments with real-world data sets were conducted and the performance of pSLEUTH measured. We conclude not only that pRPL greatly reduces the development complexity of implementing a parallel raster-processing algorithm, it also greatly reduces the computing time of computationally intensive raster-processing algorithms, as demonstrated with pSLEUTH.  相似文献   

14.
Abstract

With the increasing importance of parallel computing, attention must be given to utilising these resources efficiently. This article describes an algorithm to use cooperating parallel processors to solve the problem of vector polygon overlay, one of the most computationally-intensive problems in the GIS arena. The basic algorithm, which is described here using natural language, is not specific to a particular parallel architecture but has elements that are best suited to particular configurations, namely distributed-memory Multiple Instruction stream Multiple Data stream (MIMD) architectures. The intention is to provide an algorithm which utilises the potential of such architectures by distributing the computational load over several cooperating processors.  相似文献   

15.
准确预报无资料地区的产流产沙,对土壤侵蚀治理具有重要的实践意义。为了研究南方红壤侵蚀区无观测资料流域的产流产沙情况,以福建省长汀县朱溪小流域为研究区,其次一级流域游屋圳子流域和高陂塅子流域分别为参证流域和无观测资料流域。采用相对误差(Re)、决定系数(R2)以及Nash-Sutcliffe效率系数(Ens)评价了SWAT模型在游屋圳子流域的产流产沙模拟的适用性,基于地形指数判定了两子流域的水文相似性。结果表明:SWAT模型适用于游屋圳子流域的产流产沙模拟;游屋圳子流域与高陂塅子流域具有水文相似性,说明两子流域间可以进行模型参数移植;经模型参数移植,模拟得2010年高陂塅子流域年径流量为1.32×107m3,年产沙量为2 200 t。模拟结果不仅为小流域的水土保持治理提供参考,也为其他无资料流域的产流产沙模拟提供方法借鉴。  相似文献   

16.
Simulating urban landscape dynamics in metropolitan areas has attracted much attention lately, but the difficulty remains. Although large-scale urban simulation studies consider spatial interaction as an important factor, spatial interaction cannot be accurately measured based on a single element flow, and its effects may not strictly follow a distance decay function. Furthermore, different cities may require different transition rules. In this study, we combined bidirectional flows of population and information and an improved gravitational field model to model the urban spatial interaction, and we then integrated a partitioned cellular automata (CA) model to simulate the urban growth for different cities in the Yangtze River middle reaches megalopolis. It was found that the simulation results generated by the CA model considering spatial interaction are significantly improved. Furthermore, partitioned conversion thresholds can effectively improve the model performance. The proposed model showed a much better performance in the simulation of subordinate cities surrounding the core cities, than for the core cities and fringe cities. We suggest that large-scale urban simulation should pay more attention to the development of partitioned transition rules. The effects of intercity urban flows should also be considered in the simulation of small- and medium-sized cities near the regional cores.  相似文献   

17.
土地覆盖与气候变化对黄河源区径流的影响   总被引：1，自引：1，他引：0  
After dividing the source regions of the Yellow River into 38 sub-basins, the paper made use of the SWAT model to simulate streamflow with validation and calibration of the observed yearly and monthly runoff data from the Tangnag hydrological station, and simulation results are satisfactory.Five land-cover scenario models and 24 sets of temperature and precipitation combinations were established to simulate annual runoff and runoff depth under different scenarios. The simulation shows that with the increasing of vegetation coverage annual runoff increases and evapotranspiration decreases in the basin. When temperature decreases by 2℃ and precipitation increases by 20%,catchment runoff will increase by 39.69%, which is the largest situation among all scenarios.  相似文献   

18.
Cellular automata (CA) models can simulate complex urban systems through simple rules and have become important tools for studying the spatio-temporal evolution of urban land use. However, the multiple and large-volume data layers, massive geospatial processing and complicated algorithms for automatic calibration in the urban CA models require a high level of computational capability. Unfortunately, the limited performance of sequential computation on a single computing unit (i.e. a central processing unit (CPU) or a graphics processing unit (GPU)) and the high cost of parallel design and programming make it difficult to establish a high-performance urban CA model. As a result of its powerful computational ability and scalability, the vectorization paradigm is becoming increasingly important and has received wide attention with regard to this kind of computational problem. This paper presents a high-performance CA model using vectorization and parallel computing technology for the computation-intensive and data-intensive geospatial processing in urban simulation. To transfer the original algorithm to a vectorized algorithm, we define the neighborhood set of the cell space and improve the operation paradigm of neighborhood computation, transition probability calculation, and cell state transition. The experiments undertaken in this study demonstrate that the vectorized algorithm can greatly reduce the computation time, especially in the environment of a vector programming language, and it is possible to parallelize the algorithm as the data volume increases. The execution time for the simulation of 5-m resolution and 3 × 3 neighborhood decreased from 38,220.43 s to 803.36 s with the vectorized algorithm and was further shortened to 476.54 s by dividing the domain into four computing units. The experiments also indicated that the computational efficiency of the vectorized algorithm is closely related to the neighborhood size and configuration, as well as the shape of the research domain. We can conclude that the combination of vectorization and parallel computing technology can provide scalable solutions to significantly improve the applicability of urban CA.  相似文献   

19.
The demand for parallel geocomputation based on raster data is constantly increasing with the increase of the volume of raster data for applications and the complexity of geocomputation processing. The difficulty of parallel programming and the poor portability of parallel programs between different parallel computing platforms greatly limit the development and application of parallel raster-based geocomputation algorithms. A strategy that hides the parallel details from the developer of raster-based geocomputation algorithms provides a promising way towards solving this problem. However, existing parallel raster-based libraries cannot solve the problem of the poor portability of parallel programs. This paper presents such a strategy to overcome the poor portability, along with a set of parallel raster-based geocomputation operators (PaRGO) designed and implemented under this strategy. The developed operators are compatible with three popular types of parallel computing platforms: graphics processing unit supported by compute unified device architecture, Beowulf cluster supported by message passing interface (MPI), and symmetrical multiprocessing cluster supported by MPI and open multiprocessing, which make the details of the parallel programming and the parallel hardware architecture transparent to users. By using PaRGO in a style similar to sequential program coding, geocomputation developers can quickly develop parallel raster-based geocomputation algorithms compatible with three popular parallel computing platforms. Practical applications in implementing two algorithms for digital terrain analysis show the effectiveness of PaRGO.  相似文献   

20.
After dividing the source regions of the Yellow River into 38 sub-basins, the paper made use of the SWAT model to simulate streamflow with validation and calibration of the observed yearly and monthly runoff data from the Tangnag hydrological station, and simulation results are satisfactory. Five land-cover scenario models and 24 sets of temperature and precipitation combinations were established to simulate annual runoff and runoff depth under different scenarios. The simulation shows that with the increasing of vegetation coverage annual runoff increases and evapotranspiration decreases in the basin. When temperature decreases by 2oC and precipitation increases by 20%, catchment runoff will increase by 39.69%, which is the largest situation among all scenarios.  相似文献   

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