Geomorphological hierarchies for complex mega-dunes and their implications for mega-dune evolution in the Badain Jaran Desert

The evolution of mega-dunes is sometimes attributed to factors other than the wind but evidence for this is lacking. It is assumed that the dominance of wind in maintaining the evolution of mega-dunes should be characterized by regular height–spacing relationships that have been found for simple dunes or wind ripples which are dominantly formed by the wind. In this context, we studied the height–spacing relationship for the complex reversing mega-dunes in the Badain Jaran Desert, which features the tallest mega-dunes in the world. The complex mega-dunes were divided into three hierarchical orders according to the cumulative probability plots of dune height and spacing measurements, and the coefficients of variability of dune heights and spacings were in accordance with values reported for other deserts. The relationship between dune spacing and height for all the three orders of dunes could be expressed reasonably well by a uniform linear function that was also applied to the height–wavelength relationship for wind ripples in other deserts. This relationship was found to be similar to those for several other deserts and subaqueous bedforms. This implies that there should be few unique factors in maintaining the evolution of complex mega-dunes in the Badain Jaran Desert compared with the superimposed simple dunes and dunes in other deserts, dune fields and subaqueous bedforms, and that the tallest mega-dunes on the earth can be maintained by the wind.     

宁蒙陕甘毗邻地区沙漠旅游合作开发

跨区域沙漠旅游已成为沙漠旅游研究的新课题。本文以宁夏、内蒙古、陕西、甘肃跨区域沙漠旅游合作开发为研究对象,在剖析了4省（区）毗邻地区沙漠旅游资源总体特征、沙漠旅游开发现状及面临问题的基础上,进行了跨区域合作开发的可行性分析。认为跨区域合作开发可行性的理论依据是劳动地域分工理论和区域经济联系理论,现实分析是良好的合作基础、区位和交通优势突出、旅游资源互补性较强、沙漠旅游资源集聚程度很高。最后提出4省（区）跨区域沙漠旅游合作开发措施及旅游线路设计,并指出跨区域沙漠旅游合作开发实施中需要解决的一些问题。     

人工卵石床面风沙流粒度特征

沉积物粒径分布对风沙沉积物的起动、输送和沉降过程十分重要。不同粒径的风沙沉积物空气动力学特征不同,从而导致其起动机理、输送过程和沉降模式不同。因此,粒度可以作为风沙沉积过程的指示器。戈壁是西北地区的一种重要地貌景观,戈壁风沙流是风沙物理研究的内容之一,但目前研究较少,特别是对戈壁风沙流粒度分布的研究,几乎没有报道。本文利用人工卵石床面模拟戈壁地表,对0.25、0.5、1 m和2 m高度的风沙流粒度特征进行观测,结果表明：沙源、地表状况、风程效应等影响沙粒粒径随高度的变化。沙源近,平均粒径随高度先减小后增加;沙源远,平均粒径随高度增加减小。戈壁表面的不同区域,沙粒粒径级配不同：随高度增加,粗砂,中砂含量降低,细砂、极细砂和粉砂含量增加;随距离增加,中砂含量降低,细砂、极细砂和粉砂含量增加。平均粒径越大,分选越好,偏度越趋于正偏,峰度越趋于变宽。偏度、峰度随分选系数增加而增加。峰度随偏度增加而增加。     

基于RS和GIS的河西走廊风沙灾害风险评估

河西走廊位于中国西北干旱、半干旱区,受到周边沙漠和戈壁的影响,风沙灾害问题比较严重。依据灾害系统理论,从致灾因子危险性、孕灾环境脆弱性和承灾体易损性3个方面构建区域灾害风险评估体系和评估模型,对河西走廊风沙灾害风险进行评估。结果表明：（1）高风险地区主要分布在河西走廊内部的沙漠区,如酒泉市、玉门市、金塔县、高台县、临泽县以及武威市的北部地区,约占总面积的10.8%;（2）较高风险的地区主要分布在敦煌市、阿克塞哈萨克族自治县和河西走廊的北部,约占总面积的56.5%;（3）低风险地区位于河西走廊的东南部,该区在祁连山的天然屏障下,植被盖度高,雨水丰富;（4）作为风沙灾害的主体和对象,河西走廊的社会经济因素对风沙灾害风险的贡献率较低。而作为风沙灾害的物质基础和动力条件,沙源和风速仍是河西走廊风沙灾害风险的主要诱因;（5）经济发达城市在风沙灾害中具有更高的易损性,应该对城市邻近沙源进行重点防治。     

沙产业在内蒙古的构想与发展:生态系统服务体系视角

根据沙产业理论和生态系统服务的概念,提出沙产业生态系统服务体系理念。分析了内蒙古沙产业生态系统服务体系现状,并通过ArcGIS软件对影响内蒙古沙产业发展趋势的气候变化因素进行研究,最后分析了内蒙古沙产业发展的构想、存在的问题以及发展原则与对策。从目前发展状况和对气候变化趋势的分析,建议内蒙古沙产业发展可以在空间上由西向中、东部转移,并将其沙产业生态服务体系逐步建设完善,以推动内蒙古沙产业的健康发展,逐步提高内蒙古地区生态系统服务水平,促进沙区生态社会经济协调与可持续发展。     

巴丹吉林沙漠高大沙山沉积物粒度特征及其与植被、地貌关系

沙丘形成演变是风-沉积物-其他地理因子相互反馈作用的一个动态系统过程,粒度可以揭示其中包含的部分环境信息并被广泛应用于风沙地貌研究。本文分析了巴丹吉林沙漠伊和吉格德湖高大沙山区沉积物粒度特征及其与植被、地貌形态的关系。结果表明:迎风坡中上部及中部剖面各层沉积物主粒径均一,分别为中沙、细沙;迎风坡中下部及底部剖面细沙、中沙及粗沙等不同主粒径层交替,粒配复杂,其成因与粗沙粒保护作用、风向季节变化及地质时期气候变迁等因素有关;背风坡表层沉积物以细沙为主,趋向底部粗沙、中沙及极细砂增多,说明不同粒径对风及重力作用的响应存在差异;粒度参数散点图可以区分不同部位样品,趋向迎风坡底部剖面,沙粒分选性变差,正偏、负偏及近对称沙层交替,说明风力分选作用在不同部位差异明显及存在其他外力作用;沙层粒配影响植被多样性,迎风坡中上部中沙含量高,背风坡表层中部偏上极细沙及大于2.65 Φ细沙含量突然增加,是植被影响粒配的反映;迎风坡沉积环境的差异,说明随地质时期气候变迁,沙山形成可能经历了两个重要阶段,一是早期风力和水动力交替影响、具有风成与非风成环境交替特征的基底形成时期,二是以风力作用为主的现代沙山形成时期。     

沙漠化脆弱性的概念与评价

全球变暖背景下,气候变化和人类活动对沙漠化的影响成为可持续发展研究的热点问题.首先,本文基于对脆弱性概念发展的简要回顾,结合气候变化研究中的脆弱性,提出沙漠化脆弱性的概念和理论体系.其次,梳理国内外关于脆弱性评价的文献,依据沙漠化系统的特点阐释了沙漠化脆弱性评价体系、评价内容及评价方法.最后,列举沙漠化脆弱性研究中需要解决的问题,明确中国沙漠化脆弱性评价的未来特点和趋势.     

Measuring the velocity of sand particles in an air/particle two-phase flow: A comparison of several commonly used methods

The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods： photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer （PDA） method and Particle Image Velocimetry （PIV） method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.     

风沙流中风速廓线的数值模拟与实验验证

如何描述风沙流中被风沙运动改变了的风速廓线是风沙相互作用研究中的关键问题之一.该文中将跃移风沙流视为一种颗粒拟流体,将跃移颗粒对气流产生的阻力用颗粒流的阻力系数来表达,建立了描写两场相互作用的数学模型.颗粒流的阻力系数采用了前人在液态流化床研究中得出的阻力系数表达形式,通过引入一个修正系数,使其适用于风沙流(气-固两相流).将风沙边界层划分为跃移颗粒所产生的阻力不可忽略的内边界层和跃移颗粒阻力可以忽略但受内边界层影响的外边界层,分别建立了内边界层和外边界层的风速廓线表达式.应用所建立的数学模型,根据由风洞实验测定的跃移风沙流的浓度分布和速度分布资料,计算了跃移风沙流中的风速廓线,并与风洞实测结果进行了对比.结果表明,计算风速廓线与实测风速廓线吻合得比较好,在半对数图上均为上凸的曲线,有别于无风沙运动时的直线.跃移边界层外风速分布可较好地用对数函数来描述.对风沙流中风速廓线的进一步分析证实了风沙物理学奠基人Bagnold在其早期观测风沙流中的风速廓线时提出的"结点现象"(Bagnold结),该结点的高度随风速的增大而升高,随颗粒粒径的增大而降低.根据数值模拟和模拟实验,可以认为有风沙运动的动床剪切风速是综合反映风场与跃移层以及地表之间相互作用的物理量.     

The equilibrium gravel coverage of the deflated gobi above the Mogao Grottoes of Dunhuang, China

Blown sand has caused considerable damage to the Dunhuang Mogao Grottoes of China. Controlling the blown sand requires a clear understanding of the processes that govern its production and movement. Experiments were conducted in a wind tunnel and in the field to define the relationships between sand production and gravel coverage in the gobi above the Mogao Grottoes. The gravel that covers the gobi’s surface controls wind erosion, irrespective of its shape and size. The equilibrium coverage by gravel over which no further sand is emitted due to wind erosion increases and the equilibration time that is taken to form the equilibrium gravel coverage decreases with increasing wind velocity. Gravel coverage has reached an equilibrium state in the portion of the gobi directly above the grottoes, but decreases towards the Mingsha Mountains. Drifting sand from these mountains is the main source of sand damage at the Mogao Grottoes. If no additional sand from the mountains were supplied to the gobi, gravel pavements would reach an equilibrium level of coverage and prevent further production of blowing sand. Sand blown from the gobi represents secondary reactivation of sediments originally produced in the Mingsha Mountains. Therefore, to control the blowing sand above the Mogao Grottoes, emphasis should be placed on controlling erosion from the Mingsha Mountains rather than local erosion of sand in the gobi.