Discretization approach in integrated Hydrologic Model for surface and groundwater interaction

The commonly used discretization approaches for distributed hydrological models can be broadly categorized into four types,based on the nature of the discrete components:Regular Mesh,Triangular Irregular Networks(TINs),Representative Elementary Watershed(REWs) and Hydrologic Response Units(HRUs).In this paper,a new discretization approach for landforms that have similar hydrologic properties is developed and discussed here for the Integrated Hydrologic Model(IHM),a combining simulation of surface and groundwater processes,accounting for the interaction between the systems.The approach used in the IHM is to disaggregate basin parameters into discrete landforms that have similar hydrologic properties.These landforms may be impervious areas,related areas,areas with high or low clay or organic fractions,areas with significantly different depths-to-water-table,and areas with different types of land cover or different land uses.Incorporating discrete landforms within basins allows significant distributed parameter analysis,but requires an efficient computational structure.The IHM integration represents a new approach interpreting fluxes across the model interface and storages near the interface for transfer to the appropriate model component,accounting for the disparate discretization while rigidly maintaining mass conservation.The discretization approaches employed in IHM will provide some ideas and insights which are helpful to those researchers who have been working on the integrated models for surface-groundwater interaction.     

基于多模型的西宁市人口规模预测

人口是反映国情、国力基本情况的重要指标,是区域研究所必须考虑的重要因素之一。合理、准确地预测城市人口规模,是城市与区域规划中首先要考虑的基本问题,也是保证规划科学性与可实施性的关键性前提。以西宁市2000-2011年历年总人口为样本数据,分别构建了一元线性回归模型、马尔萨斯模型、logistic模型及GM（1,1）模型,并进行模型检验。结果表明：（1）模型均通过模型精度检验且精度较高,GM（1,1）模型拟合度最高,均误差达到0.004%,马尔萨斯模型拟合度最低,为-1.440 8%;（2）分析模型预测精度差异产生原因及适用性,表明深入、准确地分析样本数据特征,恰当选择分析方法对于控制人口预测精度尤为重要。由于西宁市2000-2011年人口样本数据在2005及2009年数据存在波动性,破坏了其与一元线性回归模型及马尔萨斯模型的拟合度,导致在4种模型中,Logistic及GM（1,1）模型预测精度较高,而GM（1,1）模预测精度最高,所以采用GM（1,1）模型进行西宁市人口预测,得到西宁市人口预测的最终结果：2012年西宁市总人口将达到225.89×10⁴人,2015年将达到233.39×10⁴人,2020年将达到246.37×10⁴人。从结果看,未来9 a西宁市人口将呈现持续平稳增长的态势,但随着时间推进人口增长速度将逐渐下降。     

基于GWR的南京市住宅地价空间分异及演变

以南京市主城区为例,在空间自相关分析和蒙特卡罗检验的基础上,构建城市住宅地价地理加权回归模型,通过2003 年、2009 年住宅地价空间分异的对比,探讨不同影响因素对住宅地价影响的空间差异性及其随时间变化的特点,揭示住宅地价及其影响因素的空间变化关系,以促进地价的科学化管理。研究表明：① 随着影响因素数量不断增加以及合理均衡分布,区域差异性缩小,一般会减弱其对地价的影响。② 随着交通条件的不断完善,导致影响因素如CBD、主干道、公交等对地价的影响程度和范围发生变化。③ 随着时间推移,城市居民逐渐注重生活质量、居住品位的提高,公园绿地对地价的影响程度超过其他公用设施。     

Comparing models of debris-flow susceptibility in the alpine environment

Debris-flows are widespread in Val di Fassa (Trento Province, Eastern Italian Alps) where they constitute one of the most dangerous gravity-induced surface processes. From a large set of environmental characteristics and a detailed inventory of debris flows, we developed five models to predict location of debris-flow source areas. The models differ in approach (statistical vs. physically-based) and type of terrain unit of reference (slope unit vs. grid cell). In the statistical models, a mix of several environmental factors classified areas with different debris-flow susceptibility; however, the factors that exert a strong discriminant power reduce to conditions of high slope-gradient, pasture or no vegetation cover, availability of detrital material, and active erosional processes. Since slope and land use are also used in the physically-based approach, all model results are largely controlled by the same leading variables.Overlaying susceptibility maps produced by the different methods (statistical vs. physically-based) for the same terrain unit of reference (grid cell) reveals a large difference, nearly 25% spatial mismatch. The spatial discrepancy exceeds 30% for susceptibility maps generated by the same method (discriminant analysis) but different terrain units (slope unit vs. grid cell). The size of the terrain unit also led to different susceptibility maps (almost 20% spatial mismatch). Maps based on different statistical tools (discriminant analysis vs. logistic regression) differed least (less than 10%). Hence, method and terrain unit proved to be equally important in mapping susceptibility.Model performance was evaluated from the percentages of terrain units that each model correctly classifies, the number of debris-flow falling within the area classified as unstable by each model, and through the metric of ROC curves. Although all techniques implemented yielded results essentially comparable; the discriminant model based on the partition of the study area into small slope units may constitute the most suitable approach to regional debris-flow assessment in the Alpine environment.     

DEM流径算法的相似性分析

流径算法是分布式水文模型、土壤侵蚀模拟等研究中的关键技术环节,决定着汇水面积、地形指数等许多重要的地形、水文参数的计算。本文以黄土高原两个典型样区的不同分辨率DEM为研究对象,对常用的五种流径算法(D8、Rho8、Dinf、MFD和DEMON)通过相对差系数、累积频率图、XY散点分布图等进行了定量的对比分析。结果表明:算法的差异主要集中在坡面区域,汇流区域各类算法的差别较小;算法差异在不同DEM尺度下都有所体现,但高分辨率下的差异会更明显;在地形复杂区域,多流向算法要优于单流向算法。研究也进一步指出汇水面积、地形指数等水文参数对流径算法具有强烈的依赖性。     

Polarimetric scattering model for estimation of above ground biomass of multilayer vegetation using ALOS-PALSAR quad-pol data

Forests are important biomes covering a major part of the vegetation on the Earth, and as such account for seventy percent of the carbon present in living beings. The value of a forest’s above ground biomass (AGB) is considered as an important parameter for the estimation of global carbon content. In the present study, the quad-pol ALOS-PALSAR data was used for the estimation of AGB for the Dudhwa National Park, India. For this purpose, polarimetric decomposition components and an Extended Water Cloud Model (EWCM) were used. The PolSAR data orientation angle shifts were compensated for before the polarimetric decomposition. The scattering components obtained from the polarimetric decomposition were used in the Water Cloud Model (WCM). The WCM was extended for higher order interactions like double bounce scattering. The parameters of the EWCM were retrieved using the field measurements and the decomposition components. Finally, the relationship between the estimated AGB and measured AGB was assessed. The coefficient of determination (R²) and root mean square error (RMSE) were 0.4341 and 119 t/ha respectively.     

Interlaboratory comparison of cosmogenic 21Ne in quartz

We performed an interlaboratory comparison study with the aim to determine the accuracy of cosmogenic ²¹Ne measurements in quartz. CREU-1 is a natural quartz standard prepared from amalgamated vein clasts which were crushed, thoroughly mixed, and sieved into 125–250 μm and 250–500 μm size fractions. 50 aliquots of CREU-1 were analyzed by five laboratories employing six different noble gas mass spectrometers. The released gas contained a mixture of 16–30% atmospheric and 70–84% non-atmospheric (predominantly cosmogenic) ²¹Ne, defining a linear array on the ²²Ne/²⁰Ne-²¹Ne/²⁰Ne three isotope diagram with a slope of 1.108 ± 0.014. The internal reproducibility of the measurements is in good agreement with the formal analytical precision for all participating labs. The external reproducibility of the ²¹Ne concentrations between labs, however, is significantly overdispersed with respect to the reported analytical precision. We report an average reference concentration for CREU-1 of 348 ± 10 × 10⁶ at [²¹Ne]/g[SiO₂], and suggest that the 7.1% (2σ) overdispersion of our measurements may be representative of the current accuracy of cosmogenic ²¹Ne in quartz. CREU-1 was tied to CRONUS-A, which is a second reference material prepared from a sample of Antarctic sandstone. We propose a reference value of 320 ± 11 × 10⁶ at/g for CRONUS-A. The CREU-1 and CRONUS-A intercalibration materials may be used to improve the consistency of cosmogenic ²¹Ne to the level of the analytical precision.     

An inter-laboratory comparison of cosmogenic 3He and radiogenic 4He in the CRONUS-P pyroxene standard

This study reports an inter-laboratory comparison of the ³He and ⁴He concentrations measured in the pyroxene material CRONUS-P. This forms part of the CRONUS-Earth and CRONUS-EU programs, which also produced a series of natural reference materials for in situ produced ²⁶Al, ¹⁰Be, ¹⁴C, ²¹Ne and ³⁶Cl.Six laboratories (GFZ Potsdam, Caltech Pasadena, CRPG Nancy, SUERC Glasgow, BGC Berkeley, Lamont New York) participated in this intercomparison experiment, analyzing between 5 and 22 aliquots each. Intra-laboratory results yield ³He concentrations that are consistent with the reported analytical uncertainties, which suggests that ³He is homogeneous within CRONUS-P. The inter-laboratory dataset (66 determinations from the 6 different labs) is characterized by a global weighted mean of (5.02 ± 0.12) × 10⁹ at g⁻¹ with an overdispersion of 5.6% (2σ). ⁴He is characterized by a larger variability than ³He, and by an inter-lab global weighted mean of (3.60 ± 0.18) × 10¹³ at g⁻¹ (2σ) with an overdispersion of 10.4% (2σ).There are, however, some systematic differences between the six laboratories. More precisely, 2 laboratories obtained mean ³He concentrations that are about 6% higher than the clustered other 4 laboratories. This systematic bias is larger than the analytical uncertainty and not related to the CRONUS-P material (see Schaefer et al., 2015). Reasons for these inter-laboratory offsets are difficult to identify but are discussed below. To improve the precision of cosmogenic ³He dating, we suggest that future studies presenting cosmogenic ³He results also report the ³He concentration measured in the CRONUS-P material in the lab(s) used in a given study.     

Numerical investigation on the impact resistance of road barriers of Micropile-MSE Wall for subgrade

The Micropile-MSE Wall, specially designed for mountain roadways, is used to simultaneously increase the MSE wall’s local stability, global stability and impact resistance of road barriers. Model tests were conducted first to validate the viability of the Micropile-MSE Wall. The impact resistance of the road barrier is then studied numerically. The test results indicate that the surcharge-induced earth pressure, base pressure and lateral displacement of Micropile-MSE Wall panels are effectively reduced. The impact loading on the barriers of the Micropile-MSE Wall is actually supported by the whole retaining structure, which increases the impact resistance of the road barrier significantly.