Small‐scale variability in surface moisture on a fine‐grained beach: implications for modeling aeolian transport     

Brandon L. Edwards  Steven L. Namikas 《地球表面变化过程与地形》2009,34(10):1333-1338

Small‐scale variations in surface moisture content were measured on a fine‐grained beach using a Delta‐T Theta probe. The resulting data set was used to examine the implications of small‐scale variability for estimating aeolian transport potential. Surface moisture measurements were collected on a 40 cm × 40 cm grid at 10 cm intervals, providing a total of 25 measurements for each grid data set. A total of 44 grid data sets were obtained from a representative set of beach sub‐environments. Measured moisture contents ranged from about 0% (dry) to 25% (saturated), by weight. The moisture content range within a grid data set was found to vary from less than 1% to almost 15%. The magnitude of within‐grid variability varied consistently with the mean moisture content of the grid sets, following an approximately normal distribution. Both very wet and very dry grid data sets exhibited little internal variability in moisture content, while intermediate moisture contents were associated with higher levels of variability. Thus, at intermediate moisture contents it was apparent that some portions of the beach surface could be dry enough to allow aeolian transport (i.e. moisture content is below the critical threshold), while adjacent portions are too wet for transport to occur. To examine the implications of this finding, cumulative distribution functions were calculated to model the relative proportions of beach surface area expected to be above or below specified threshold moisture levels (4%, 7%, and 14%). It was found that the implicit inclusion of small‐scale variability in surface moisture levels typically resulted in changes of less than 1% in the beach area available for transport, suggesting that this parameter can be ignored at larger spatial scales. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

节理化工程岩体成型爆破技术研究   总被引：1，自引：0，他引：1  

何满潮  王成虎  李小杰 《岩土力学》2004,25(11):1749-1753

通过对光面爆破技术在节理化岩体中实施爆破方案的不足之处的分析,引入了双向聚能拉伸爆破技术,并简要分析和介绍了该技术的基本技术原理和优点以及两种爆破设计方案,同时对该技术在两个大型洞室工程中的高岩台应用情况进行了分析和介绍,最后就该技术的今后的研究方向提出了一些设想。  相似文献   

重叠区域伪谱法计算非均匀地球介质地震波传播          下载免费PDF全文

严九鹏  王彦宾 《地震学报》2008,30(1):47-58

伪谱法是一种高效、高精度计算非均匀介质地震波传播的数值算法,由于它的微分算子的全局性,一般认为该方法不适于并行计算. 本文介绍了并行计算非均匀介质中地震波传播的重叠区域分解算法,给出了一种基于傅里叶伪谱法的并行算法. 文中给出的算法将介质划分为相互重叠的若干区域,在各个子域上单独求解,利用重叠部分的解的传递,将各个子域连接起来,实现了伪谱法在分布式并行处理机上的计算. 文中给出了一个将二维区域分解的算例,比较了并行算法和整体算法的结果,分析了并行算法的计算精度. 结果表明,并行算法会有效降低计算时间,并且保证计算精度. 该方法在大规模三维非均匀介质的地震波场模拟方面有应用价值.   相似文献   

重磁场多尺度分析原理   总被引：1，自引：0，他引：1  

李健  周云轩  卢焱 《世界地质》2000,19(4):379-384,391

介绍了连续小波变换,离散小波变换,框架理论和多分辨分析（多尺度分析）等小波分析的基本方法原理以及第二代小波（升降方案）,以及近年来小波分析在重磁场中的应用成果（包划常识别,异常分离,信号云噪,重磁下延,反演成像等方面）。在对其进行仔细分析的基础上,指出目前小波分析在重磁场领域应用中存在的问题,诸如如何选择一个较优的小波母函数,并提出相应的解决思路－模型小波。  相似文献   

二维扩散输移问题的一种新的有限体积算法   总被引：1，自引：0，他引：1  

江春波  杜丽惠 《水科学进展》2000,11(4):351-356

从空间离散格式上比较了有限元格式与有限体积格式的异同处,证明有限体积格式是有限元格式的一种特例,有限元格式也是一种守恒型格式。并根据有限元格式与有限体积格式的比较,提出了一种新的高精度、稳定性好的有限体积格式。通过模拟非定常的纯对流方程和二维对流扩散方程,证明了有限体积格式的优点。  相似文献   

Solving the Buckley–Leverett equation with gravity in a heterogeneous porous medium     

E.F. Kaasschieter 《Computational Geosciences》1999,3(1):23-48

Immiscible two‐phase flow in porous media can be described by the fractional flow model. If capillary forces are neglected, then the saturation equation is a non‐linear hyperbolic conservation law, known as the Buckley–Leverett equation. This equation can be numerically solved by the method of Godunov, in which the saturation is computed from the solution of Riemann problems at cell interfaces. At a discontinuity of permeability this solution has to be constructed from two flux functions. In order to determine a unique solution an entropy inequality is needed. In this article an entropy inequality is derived from a regularisation procedure, where the physical capillary pressure term is added to the Buckley‐Leverett equation. This entropy inequality determines unique solutions of Riemann problems for all initial conditions. It leads to a simple recipe for the computation of interface fluxes for the method of Godunov. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

THE FORMULATION OF FIDELITY SCHEMES OF PHYSICAL CONSERVATION LAWS AND IMPROVEMENTS ON A TRADITIONAL SPECTRAL MODEL OF BAROCLINIC PRIMITIVE EQUATIONS FOR NUMERICAL PREDICTION     

钟青 《Acta Meteorologica Sinica》1999,(2)

In this paper,two formulation theorems of time-difference fidelity schemes for generalquadratic and cubic physical conservation laws are respectively constructed and proved,with earliermajor conserving time-discretized schemes given as special cases.These two theorems can providenew mathematical basis for solving basic formulation problems of more types of conservative time-discrete fidelity schemes,and even for formulating conservative temporal-spatial discrete fidelityschemes by combining existing instantly conserving space-discretized schemes.Besides.the twotheorems can also solve two large categories of problems about linear and nonlinear computationalinstability.The traditional global spectral-vertical finite-difference semi-implicit model for baroclinicprimitive equations is currently used in many countries in the world for operational weatherforecast and numerical simulations of general circulation.The present work,however,based onTheorem 2 formulated in this paper,develops and realizes a high-order total energy conservingsemi-implicit time-difference fidelity scheme for global spectral-vertical finite-difference model ofbaroclinic primitive equations.Prior to this,such a basic formulation problem remains unsolved forlong,whether in terms of theory or practice.The total energy conserving semi-implicit schemeformulated here is applicable to real data long-term numerical integration.The experiment of thirteen FGGE data 30-day numerical integration indicates that the newtype of total energy conserving semi-implicit fidelity scheme can surely modify the systematicdeviation of energy and mass conserving of the traditional scheme.It should be particularly notedthat,under the experiment conditions of the present work,the systematic errors induced by theviolation of physical laws of conservation in the time-discretized process regarding the traditionalscheme designs(called type Z errors for short)can contribute up to one-third of the totalsystematic root-mean-square(RMS)error at the end of second week of the integration and exceedone half of the total amount four weeks afterwards.In contrast,by realizing a total energyconserving semi-implicit fidelity scheme and thereby eliminating corresponding type Z errors,roughly an average of one-fourth of the RMS errors in the traditional forecast cases can be reducedat the end of second week of the integration,and averagely more than one-third reduced at integraltime of four weeks afterwards.In addition,experiment results also reveal that,in a sense,theeffects of type Z errors are no less great than that of the real topographic forcing of the model.The prospects of the new type of total energy conserving fidelity schemes are very encouraging.  相似文献   

筛选法——一种矿产预测新方案的概念和原理          下载免费PDF全文

陈明  范继璋 《地球科学》1999,24(1):79-82

矿产资源体的形成受一定的成矿条件和控矿因素约束．这些约束条件可以分为成矿必要条件和成矿充分条件两大类．必要条件决定了资源体能否形成,充分条件决定了资源体的具体经济指标．利用某个成矿必要条件可把研究区内的所有单元分成“可能成矿单元”和“非成矿单元”两大部分．通过多个成矿必要条件的逐步筛选,又可从“可能成矿单元”中进一步提取“成矿单元”,从而实现矿产资源的定性预测．把所有单元通过如上所述的筛选过程并提取“成矿单元”的方法称为“筛选法”（ｓｉｆｔｉｎｇｓｃｈｅｍｅ）．在模型矿床存在的条件下,可通过充分条件在地质变量和资源量之间进行数字建模,并对未知“成矿单元”进行定量评价．研究表明,筛选法有可能为采矿企业提供更可靠的找矿靶区．  相似文献   

26000kN垂直静载荷试验设计方案及成果初探     

叶建辉  黄清和 《水文地质工程地质》1999,26(4):13-15

本文通过在漳州某电厂实施２６０００ｋＮ基桩垂直静载荷试验项目,在此对国内最大吨位静载荷试验的组织设计方案和试验方法（锚桩法）进行介绍,并简介试验成果,以供同行参考,并提出宝贵意见。  相似文献   

热带海洋SSTA的POP中性预测方案     

李丽平  王盘兴  吴洪宝 《南京气象学院学报》1999,22(3):360-366

用主振荡型（ Ｐ Ｏ Ｐ）方法分析了热带洋区月平均海表温度异常（ Ｓ Ｓ Ｔ Ａ）。结果表明,最重要的 ４ 个传播型 Ｐ Ｏ Ｐ对与 Ｅｌ Ｎｉｎｏ／ Ｌａ Ｎｉｎａ 事件关系密切,说明这类事件具有复杂的时空结构。在此基础上,给出了一个能定量地综合多个传播型 Ｐ Ｏ Ｐ对作用的 Ｐ Ｏ Ｐ中性预测方案。非独立样本和独立样本试验表明,它具有 ４ 个月的预测时效,且其预测能力在 Ｓ Ｓ Ｔ 强异常的 Ｅｌ Ｎｉｎｏ、 Ｌａ Ｎｉｎａ 事件阶段强于弱异常的非 Ｅｌ Ｎｉｎｏ／ Ｌａ Ｎｉｎａ 事件阶段。  相似文献