Effects of non-Gaussian copula-based hydraulic conductivity fields on macrodispersion
Effects of non-Gaussian copula-based hydraulic conductivity fields on macrodispersion
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DOI：
10.1029/2011wr011425
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发表时间：
2012-07-11
影响因子：
5.4
通讯作者：
Sudicky, E. A.
中科院分区：
文献类型：
--
作者：
Haslauer, C. P.;Guthke, P.;Sudicky, E. A.
这是适合现实世界数据集的空间 copula 模型的应用。 copula 模型允许对独立于边缘分布的纯空间依赖性进行建模。使用非高斯联结模型证明了博登含水层的空间依赖性结构明显是非高斯的——尽管博登含水层通常被认为是相对均匀的多孔介质，其导水率方差较小。除了使用联结函数评估 Borden 水力传导率数据集的空间依赖性结构之外，本研究的目标是探索水力传导率场的结构是否影响物理特性，例如通过浓度场的第二空间中心矩评估的羽流演化。为了进行比较，将两种类型的水力传导率场拟合到 Borden 水力传导率数据集：一种具有高斯依赖性，另一种具有非高斯类型依赖性。这两种类型的水力传导率场的构造使其二阶空间矩相同，因此无法通过基于半变异函数的地质统计学来区分它们。本文说明了 Borden 水力传导率数据集的空间依赖结构明显是非高斯的。尽管 Borden 是一种相对均匀的多孔介质，并且尽管两种类型的空间场无法通过其变差函数来区分，但基于这两种类型的各向同性场的溶质输运特性在二维环境中存在显着差异。在具有各向异性的三维空间中，这种差异不太明显。据推测，水力传导率的非高斯空间依赖性和水力传导率的更偏斜的边缘分布将对其他更异质的含水层产生重大影响。
This is an application of a spatial copula model that is fitted to a real world data set. The copula model allows modeling of pure spatial dependence independently of the marginal distribution. Using non-Gaussian copula models it is demonstrated that the spatial dependence structure of the Borden aquifer is significantly non-Gaussian-despite the fact that the Borden aquifer is commonly thought of as a relatively homogeneous porous medium with a small variance of hydraulic conductivity. In addition to evaluating the spatial dependence structure of the Borden hydraulic conductivity data set using copulas, goal of this study is to explore if the structure of the hydraulic conductivity field influences a physical property, such as plume evolution as evaluated by second spatial central moments of concentration fields. For this comparison, two types of hydraulic conductivity fields were fitted to the Borden hydraulic conductivity data set : one with a Gaussian and the other with a non-Gaussian type of dependence. These two types of hydraulic conductivity fields were constructed such that their second-order spatial moments are identical, and hence they cannot be distinguished by semivariogram-based geostatistics. This paper illustrates that the spatial dependence structure of the Borden hydraulic conductivity data set is significantly non-Gaussian. Despite the fact that Borden is a relatively homogeneous porous medium, and despite the fact that both types of spatial fields are not distinguishable by their variograms, the solute transport characteristics based on these two types of isotropic fields differ significantly in two-dimensional settings. The difference is less pronounced in three-dimensions with anisotropy. It is postulated that non-Gaussian spatial dependence of hydraulic conductivity and a more skewed marginal distribution of hydraulic conductivity will have significant implications in the other more heterogeneous aquifers.