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摘要:
集合卡尔曼滤波(ensemble Kalman filter, EnKF)是最流行的数据同化方法之一。然而,在处理非高斯问题时,EnKF存在局限性。为了解决非高斯问题并准确描述含水介质连通性,将正态分数变换(normal-score transformation, NST)与多重数据同化集合平滑器(ensemble smoother with multiple data assimilation, ES-MDA)相结合,提出NS-ES-MDA方法。通过对比实验,验证了NS-ES-MDA方法估计非高斯分布含水层渗透系数场的有效性。相较于重启正态分数集合卡尔曼滤波器(restart normal-score ensemble Kalman filter, rNS-EnKF)方法,NS-ES-MDA在吸收相同数据后,参数估计精度提升约34%,计算效率提升约35%。此外,NS-ES-MDA方法受“异参同效”现象的影响较小,具有较强的更新能力,能够保障得到较准确的参数估计值。研究可为非高斯分布含水层参数估计提供一种有效的求解方法。
Abstract:The ensemble Kalman filter (EnKF) is one of the most widely used data assimilation methods. However, it exhibits limitations in handling non-Gaussian problems. To effectively address such issues and accurately describe the connectivity of aquifers, a novel approach named NS-ES-MDA is developed in this study. The proposed NS-ES-MDA synergistically combines the normal-score transformation (NST) with ensemble smoother with multiple data assimilation (ES-MDA). Through comparative experiments, the efficacy of NS-ES-MDA in estimating the hydraulic conductivity of non-Gaussian distributed aquifers is demonstrated. By assimilating the same dataset, NS-ES-MDA exhibits approximately 34% improvement in parameter estimation accuracy and about 35% enhancement in computational efficiency compared to the restart normal-score ensemble Kalman filter (rNS-EnKF). Furthermore, the NS-ES-MDA shows case robustness against the “equifinality” and displays remarkable updating capabilities, which leads to more precise parameter estimates. This study provides an effective solution for parameter estimation in non-Gaussian distributed aquifers.
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表 1 二维算例对数渗透系数参考场参数设置
Table 1. Parameters of the reference lnK
岩性 变异函数
类型均值
/(m·d−1)标准差
/(m·d−1)x方向
变程/my方向
变程/m砂土 指数型 2.0 0.5 200 200 黏土 指数型 −1.5 0.5 200 200 表 2 二维算例含水层渗透系数场估计的情景设置及估计结果
Table 2. Estimation of the two-dimensional aquifer hydraulic conductivity field in different scenarios
情景 方法
(迭代次数)IRMSE(lnK)
/(m·d−1)IES(lnK)
/(m·d−1)运行
时间/s与S0的
比值/%S0 rNS-EnKF() 1.38 1.19 1680 100% S1 NS-ES-MDA(1) 1.40 1.31 254 15% S2 NS-ES-MDA(2) 1.28 1.18 354 21% S3 NS-ES-MDA(4) 1.05 0.95 628 37% S4 NS-ES-MDA(6) 0.92 0.82 901 54% S5 NS-ES-MDA(8) 0.91 0.76 1084 65% S6 NS-ES-MDA(10) 0.92 0.74 1285 76% 注:rNS-EnKF不是迭代算法,没有迭代次数;IRMSE(lnK)代表集合均值与真实lnK值的均方根误差;IES(lnK)是后验参数集合的集合扩散;运行时间指在CPU主频为3.80 GHz的计算机上运行所用时间;与S0的比值为不同情景运行时间与S0运行时间的比值。 表 3 水头控制点处评价指标
Table 3. Metrics at head control points
评价指标 初始集合 S0 S1 S2 S3 S4 S5 S6 IRMSE(Head #1)/m 12.10 1.07 38.00 5.82 1.03 0.70 0.24 1.22 IES(Head #1)/m 27.88 4.47 50.17 18.28 8.53 6.27 5.51 5.03 INSE(Head #1) 0.03 0.99 −8.59 0.78 0.99 1.00 1.00 0.99 IRMSE(Head #2)/m 57.96 3.14 230.50 41.99 5.30 6.14 3.00 1.42 IES(Head #2)/m 50.92 12.54 202.68 76.99 26.19 14.53 9.68 8.84 INSE(Head #2) 0.72 1.00 −3.40 0.85 1.00 1.00 1.00 1.00 IRMSE(Head #3)/m 123.40 9.81 416.68 72.18 19.15 24.69 11.03 3.89 IES(Head #3)/m 100.99 17.04 255.07 98.46 38.17 21.65 13.06 12.09 INSE(Head #3) 0.70 1.00 −2.42 0.90 0.99 0.99 1.00 1.00 表 4 浓度控制点处的评价指标
Table 4. Metrics at concentration control points
评价指标 初始集合 S0 S1 S2 S3 S4 S5 S6 IRMSE(Conc #4)/(g·m−3) 4.57 3.80 3.28 2.41 1.25 0.89 0.84 0.71 IES(Conc #4)/(g·m−3) 6.58 2.69 4.72 3.19 1.29 0.84 0.79 0.75 INSE(Conc #4) −0.21 0.42 0.57 0.75 0.92 0.97 0.96 0.97 IRMSE(Conc #5)/(g·m−3) 1.86 2.74 3.09 2.54 0.80 0.28 0.24 0.25 IES(Conc #5)/(g·m−3) 2.61 1.64 2.18 1.84 0.99 0.55 0.38 0.33 INSE(Conc #5) 0.34 0.79 0.67 0.72 0.95 0.99 0.99 0.99 IRMSE(Conc #6)/(g·m−3) 25.12 26.63 28.40 28.07 27.79 18.57 9.99 6.84 IES(Conc #6)/(g·m−3) 13.19 8.82 9.77 8.61 7.96 6.76 6.22 5.58 INSE(Conc #6) −0.21 −0.83 −1.06 −0.98 −1.06 0.57 0.99 1.00 -
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