对流边界层的大涡模拟研究

本文建立了一个均匀平坦地面上对流边界层的大涡模式,模式考虑了水汽,采用了考虑浮力和固壁影响订正的一阶闭合。并用所建模式进行了由热扰动发展的对流边界层的模拟及其对地表热状况变化响应的初步探讨性模拟工作。通过模拟认为,模式较好地反映了对流边界层的主要结构。     

沙漠绿洲不同下垫面夏季能量收支对比分析

利用"绿洲系统能量与水分循环过程观测试验"2005年在甘肃金塔不同下垫面的观测资料,对绿洲、戈壁和沙漠不同下垫面夏季辐射和地表能量收支及闭合特征进行了全面的时空对比分析,结果表明:(1)不同下垫面太阳向下短波辐射没有明显差距,地面短波向上辐射差别较大,大气长波向下辐射变化较小,地表长波辐射差异显著.另外,地表吸收辐射戈壁沙漠日变化较绿洲显著.(2)沙漠与戈壁各通量特征相似,而与绿洲上的有很大差异.(3)能量通量测量存在明显的不确定性:影响能量通量不闭合的原因,主要是超声和土壤热通量的测量误差.     

春末黄土高原半干旱区地表能量闭合的观测研究

利用兰州大学半干旱气候与环境监测站的连续观测数据,分析了该站的数据质量情况和黄土高原半干旱区的近地层湍流通量特征及地表能量平衡能量闭合状况.结果表明:兰州大学半干旱气候与环境监测站(SACOL)湍流通量的平均时间取30min为宜.该站利用EdiRe获得的湍流通量较TK2和CR5000数据自动记录器输出的湍流通量结果要好.黄土高原半干旱区近地层湍流能量与地表含水量状况明显相关,地表干燥时感热通量处于主导地位,接近于干旱区的特征;地表湿润时感热通量和潜热通量则相当,接近于湿润地区的特征.地表能量平衡分析表明,兰州大学黄土高原半干旱环境监测站观测的地表能量闭合度高达85%,与已有的观测相比,能量闭合情况属于较好水平.     

利用排驱压力研究断裂封闭性及其在塔里木盆地北部地区的应用

排驱压力是实现油气二次运移所需的最小驱动力,是研究油气二次运移和评价封堵能力的主要指标。断裂的封闭和开启性取决于断裂两侧和断裂带内物质之间差异排驱压力的大小,差值愈大,断裂封闭性愈好,反之愈差。但断裂的封闭性不是一成不变的,一旦油气聚集超过了由差异排驱压力控制的油气柱高度时,断裂将显示开启性;另外,随断裂发育时间和部位的不同,封闭性也不一样。本文着重研究塔里木盆地北部柯坪南缘断裂、印干断裂、库鲁克乌居木等断裂的封闭性问题,并考虑该区压力封闭的下限值及油气流动r_c30下限值,研究结果与实际地质调查相吻合。这一研究方法为今后在塔里木盆地北部油区全面开展断裂封闭性研究提供了新的思路,具有重要的理论意义.      

锡石U-Pb同位素体系的封闭性及其测年的可靠性分析

锡石是各种不同类型锡矿床中最重要的矿石矿物,其U-Pb/Pb-Pb同位素年代学研究对于精确厘定锡矿床的成矿时代以及进一步揭示其矿床成因等具有重要意义.本文通过计算锡石中Pb的扩散参数,从扩散动力学角度对U-Pb同位素体系的封闭性进行了研究,探讨了不同温度条件下锡石对其所含U-Pb同位素信息的保存能力.研究结果表明,锡石...     

Evaluating Models of The Neutral, Barotropic Planetary Boundary Layer using Integral Measures: Part I. Overview

Data for the cross-isobaric angle ₀, the geostrophic drag coefficient C_g, and the functions A and B of Rossby number similarity theory, obtained from meteorological field experiments, are used to evaluate a range of models of the neutral, barotropic planetary boundary layer. The data give well-defined relationships for ₀, C_g, and the integrated dissipation rate over the boundary layer, as a function of the surface Rossby number. Lettau's first-order closure mixing-length model gives an excellent fit to the data; other simple models give reasonable agreement. However more sophisticated models, e.g., higher-order closure, large-eddy simulation, direct numerical simulation and laboratory models, give poor fits to the data. The simplemodels have (at least) one free parameter in their turbulence closure that is matched toatmospheric observations; the more sophisticated models either base their closure onmore general flows or have no free closure parameters. It is suggested that all of theatmospheric experiments that we could locate violate the strict simplifying assumptionsof steady, homogeneous, neutral, barotropic flow required by the sophisticated models.The angle ₀ is more sensitive to violations of the assumptions than is C_g.The behaviour of the data varies in three latitude regimes. In middle and high latitudes the observed values of A and B exhibit little latitudinal dependence; the best estimates are A = 1.3 and B = 4.4. In lower latitudes the neutral, barotropic Rossby number theory breaks down. The value of B increases towards the Equator; the determination of A is ambiguous – the trend can increase or decrease towards the Equator. Between approximately 5° and 30° latitude, the scatter in the data is thought to be primarily due to the inherent presence of baroclinicity. The presence of the trade-wind inversion, thermal instability and the horizontal component of the Earth's rotation _H also contribute.Marked changes in the values of A and B occur in the region between the Equator andapproximately 5° latitude, as the Coriolis parameter |f| approaches zero. Although the variation of A and B with latitude suggests some similarity to the results obtained from the direct numerical simulations, the presence of additional complexities in the real atmosphere that are not included in the numerical model, precludes a meaningful direct comparison.     

Highly retentive core domains in K-feldspar and their implications for 40Ar/39Ar thermochronology illustrated by determining the cooling curve for the Capoas Granite,Palawan, The Philippines

K-feldspar from the late Miocene Capoas Granite on Palawan in The Philippines appears to contain highly retentive diffusion domains that are closed to argon diffusion at near-solidus temperatures during cooling of this ～7 km-diameter pluton. This is an important result, for K-feldspar is commonly considered not retentive in terms of its ability to retain argon. Closure temperatures for argon diffusion in K-feldspars are routinely claimed to be in the range ～150–400°C but the release of ³⁹Ar from irradiated K-feldspar during furnace step-heating experiments in vacuo yields Arrhenius data that imply the existence of highly retentive core domains, with inferred closure temperatures that can exceed ～500–700°C. These high closure temperatures from the Capoas Granite K-feldspar are consistent with the coincidence of ⁴⁰Ar/³⁹Ar ages with U–Pb zircon ages at ca 13.5 ± 0.2 Ma. The cooling rate then accelerated, but the rate of change had considerably slowed by ca 12 Ma. Low-temperature (U–Th)/He thermochronology shows that the cooling rate once again accelerated at ca 11 Ma, perhaps owing to renewed tectonic activity.     

Numerical simulation on the cracking and failure law of compacted clay lining in landfill closure cover system

According to the mass conservation equation of solid phase, water transport, air migration and enthalpy balance equations in a deformable and unsaturated porous medium, and the mechanics model, a thermal‐hydro‐mechanical (THM) coupling mathematical model is developed in order to accurately predict the crack propagation of the compacted clay lining (CCL) in a landfill closure cover system. Numerical simulation analysis of the cracking and failure of the CCL in a landfill closure cover system under complex conditions (landfill gas pressure, variation of soil surface temperature, moisture loss of coverage soil, and uneven settlement of landfilled MSW (municipal solid waste)) is performed. The results show that the cracks are discovered firstly on the soil surface and then extend to the deeper cover system and became bigger. The cracks had broken through the closure cover system at 30 days. Over the depth range of 0.06 m, the change rate of settlement is found to be the highest because of the strong influence of temperature. The rise of temperature around the cracks is fast when the CCL is broken through by the cracks. There is a hollow area near the cracks over the depth range from 0.15 to 0.7 m, and the temperature stabilize at around 11°C without any obvious reduction. Under the condition of evaporation, the main crack in the CCL is similar to a pumping well, which causes more rapid moisture content reduction around the cracks. Vertical deformation increases linearly with depth in the process of deformation and cracking of CCL induced by uneven settlement of landfilled MSW. Copyright © 2014 John Wiley & Sons, Ltd.     

尾矿库闭库复垦及生态重建

矿业开发产生大量尾矿导致了严重的环境生态问题,尾矿是工业固体废弃物的主要来源,尾矿库占用大量的土地资源,在"人口、土地、资源"问题日益突出的今天,恢复并再利用这宝贵的二次资源将是必要的战略选择。尾矿库闭库复垦及生态重建在矿山生态环境治理方面起着重要的作用。尾矿库闭库复垦难度比较大,简单介绍了国内外尾矿库闭库复垦及生态重建的现状,并对尾矿库闭库复垦及生态重建的涵义、尾矿库闭库复垦前提条件、影响因素、闭库复垦利用方式及其技术进行了初步探讨。     

DISARMING NATURE: CONVERTING MILITARY LANDS TO WILDLIFE REFUGES*

Since 1988 the United States has closed nearly two dozen major military installations and reclassified them as national wildlife refuges. By presenting a case study of one site of military‐to‐wildlife conversion, this article examines the formation of these places and the implications of casting military practices and environmental conservation as compatible activities. As lands where military and environmental attributes can be perceived as inseparable, military‐to‐wildlife sites exemplify hybrid geographies that challenge dualistic notions of nature and society.