Temporal and spatial variations of runoff and rainwash erosion on an agricultural field

This paper investigates the spatial and temporal variations of runoff, erosion and rate of sediment transport on an agricultural field submitted to natural rainfalls. The site, located in the Eastern Townships (Québec, Canada), is a corn field (10000 m²) where sheetwash erosion is active. Water (Q) and sediment (Qs) discharges were measured from June to October at eight locations on the field and for ten rainfall events. Analysis of the data was carried out on an aggregate data set and on the distributed measurements in time and space. The results showed that changes in vegetation, soil compaction and crusting are critical in determining temporal variations of runoff and erosion. Until August, the increase in soil compaction reduced infiltration capacity and depression storage and generated greater runoff for a given rainfall intensity (I). Sediment transport decreased as particle detachment is less likely to occur when vegetation breaks the drop impact and the soil surface is sealed. Later in the season, we observed an increase in sediment concentration associated with the presence of burrowing insects and harvest activity, providing loose sediments to the broken down surface. Intercepts and slopes of the relationship between Q and Qs also vary during the period of measurement. High sediment availability over the soil surface in June and October gives high intercept values. The slope of the relationship is more stable but difficult to estimate for extreme events (high values of I or low Q values) where the number of sampled points are small. During a rainfall, the response of the field is dominated by the topography and drainage area. The largest amount of runoff and erosion occurred on straight and steep slopes with small drainage areas, and on converging gentle slopes with large drainage areas. Although aggregate runoff and erosion values are decreasing with drainage area, parameters of the Qs-Q relationship for different locations on the field are not statistically different. These results bear important consequences for models of sheetwash erosion on agricultural fields.     

成都地面气温与风速年极大值的渐近分布及参数估计

利用１９３３～１９９２年期间成都地面最高气温和地面最大风速年极值的记录，通过统计推断，找出了成都地面最高气温年极值和地面最大风速年极值遵循的渐近分布——Ｗｅｉｂｕｌ分布和Ｇｕｍｂｅｌ分布，并讨论了它们的参数估计方法。     

Non‐linear prestack seismic inversion with global optimization using an edge‐preserving smoothing filter

Estimating elastic parameters from prestack seismic data remains a subject of interest for the exploration and development of hydrocarbon reservoirs. In geophysical inverse problems, data and models are in general non‐linearly related. Linearized inversion methods often have the disadvantage of strong dependence on the initial model. When the initial model is far from the global minimum, inversion iteration is likely to converge to the local minimum. This problem can be avoided by using global optimization methods. In this paper, we implemented and tested a prestack seismic inversion scheme based on a quantum‐behaved particle swarm optimization (QPSO) algorithm aided by an edge‐preserving smoothing ( EPS) operator. We applied the algorithm to estimate elastic parameters from prestack seismic data. Its performance on both synthetic data and real seismic data indicates that QPSO optimization with the EPS operator yields an accurate solution.     

Inverse determination of soil density and stress state using dispersion wave measurements and cone penetration tests in a non-layered soil

The determination of the void ratio and stress state distribution in undisturbed soil is still an ambitious aim which cannot be reached by sampling from bore holes. Therefore, an alternative method is proposed to determine soil density and stress state using dispersion wave measurements and cone penetration tests. Dispersion wave measurements and resonant-column tests are carried out to measure the shear wave velocity and shear modulus distribution with depth. Using finite element calculations a relationship between cone penetration resistance, stress state and void ratio is derived. From these results the void ratio distribution and the stress state can be calculated inversely. The inverse method is applied to real test data. The results of the inverse parameter determination are shown and assessed regarding the possibilities and the limitations of the presented method.     

Adaptive multi-scale parameterization for one-dimensional flow in unsaturated porous media

In the analysis of the unsaturated zone, one of the most challenging problems is to use inverse theory in the search for an optimal parameterization of the porous media. Adaptative multi-scale parameterization consists in solving the problem through successive approximations by refining the parameter at the next finer scale all over the domain and stopping the process when the refinement does not induce significant decrease of the objective function any more. In this context, the refinement indicators algorithm provides an adaptive parameterization technique that opens the degrees of freedom in an iterative way driven at first order by the model to locate the discontinuities of the sought parameters. We present a refinement indicators algorithm for adaptive multi-scale parameterization that is applicable to the estimation of multi-dimensional hydraulic parameters in unsaturated soil water flow. Numerical examples are presented which show the efficiency of the algorithm in case of noisy data and missing data.     

用一种插值方法作短期气候预测的试验

将ｓｈｅｐａｒｄ插值方法运用到短期气候预测中,建立一类非模式预报方法,按照相似原因将产生相似结果的原理来作预报,对云南降水进行了预报试验。结果表明,这种方法与多元回归相比具有良好的预报能力,值得进一步探讨和应用。     

CoLM 模拟土壤温度和湿度最敏感参数的研究

合理的参数估计是提高陆面模式模拟能力的关键,而其过高的维数极大地增加了合理估计的难度。参数的敏感性分析,旨在针对目标变量找出最敏感的参数,从而实现在有限计算机资源条件下,对参数进行合理估计。本文以Common Land Model(CoLM)为研究对象,利用Morris 方法定性地从40 个参数中筛选出影响土壤温度和土壤湿度的敏感参数,并通过Sobol' 方法从敏感性顺序和各敏感参数的累积贡献率两个方面,对Morris 方法分析结果进行验证。在此基础上,本研究还利用Sobol' 方法对已筛选的参数做定量敏感性分析,最终确定参数的主效应、交互效应和总效应。研究结果表明,Morris 方法可以基于少量样本实现复杂的陆面模式的参数筛选,而Sobol' 方法的结果又从定量的角度描述了每个敏感参数对模型响应的影响程度,并且两种方法结论一致。     

The thermal regime of the Northeastern-German Basin from 2-D inversion

The thermal regime and the distribution of heat flow at the base of sedimentary basins is fundamental to the understanding of the process of basin evolution and the associated mobilization and migration of hydrocarbon and other fluids. For the Northeastern-German sedimentary basin, available information on structure, temperature, and thermal properties along a seismic DEKORP reflection profile allow high resolution 2-D forward and inverse simulations. This approach is attractive in situations where much information is available, if only with considerable uncertainty. In particular, this allows to introduce “soft” information into the analysis. In our case, forward simulations yield initial a priori estimates of the parameters while inversion calculations yield a posteriori estimates of the parameters and their uncertainty. The a priori parameters as well as their assumed uncertainty are input for a Bayesian parameter estimation scheme. In respect to the Northeastern-German sedimentary basin, the inverse analysis postulates a significant and characteristic a posteriori variation of thermal conductivity of the Zechstein unit along the entire profile as well as a generally large a posteriori thermal conductivity of the (pre-Permian) basement in the northern part of the basin. For inverse calculations, we used two alternative scenarios: One assumes the thermal conductivity of the Zechstein unit to be homogeneous along the profile while the other allows a lateral variation. A posteriori heat flow across the base of the model varies from 40 to 60 and 50 to 65 mW m⁻² for models in which values for thermal conductivity and radiogenic heat generation rate were either based on literature values or direct measurements, respectively.     

基于区间序列的GM(1.1)地下水水位预测

为探讨基于区间序列的GM（1.1）模型预测地下水水位的准确性和信息量,本文选取界点建模、转换建模和参数建模3种区间方法进行比较和分析,结果表明：界点的相对误差均值都小于0.01%,区间相对误差均值小于7%;区间序列的GM（1.1）模型具有一定的延迟效应和紊乱效应;实际水位值波动幅度较小时模型预测精度较高;参数建模的预测精度较优于界点建模和转换建模。与点预测相比,区间序列的GM（1.1）模型预测的地下水水位变化规律更有利于地下水资源管理与开发利用。     

Extraction and Analysis of Land Cover Heterogeneity over China

Spatial heterogeneity exists in land surface at every scale, and it is one of key factors to bring uncertainty to land parameter retrieval from remote-sensed data. This paper proposed a methodology to use the boundary length among different land cover types to characterize and quantify land surface heterogeneity based on high-resolution land cover images. Then the heterogeneity feature at 1 kilometer scale in China was extracted from “GlobalLand30” land cover datasets with the spatial resolution of 30 m. The mixed structure, degree of fragmentation and intra-heterogeneity of eight main vegetation biomes from MODIS land cover product over heterogeneous surface in china were analyzed. Mountain area and ecotone are more heterogeneous than other regions. Savanna biome (average boundary length is 7 426 meters) is the most heterogeneous zone followed by forest, grass/crop and shrub biome with average boundary length of 4 323, 3 160, 1 779 meters, respectively.