沙漠中公路隧道修建可行性研究     

吴楚钢  彭连杰  李贵乾  文栋良  刘飞  李强 《中国沙漠》2011,30(3):563-566

 改善沙漠地区交通是保证沙漠地区经济发展与繁荣的先决条件。开展沙漠地区交通建设刻不容缓。现阶段沙漠地区高等级公路存在的问题,并基于沙漠中的自然特征,提出了一种崭新的沙漠公路隧道设计方案。设计方案中充分展示环保节能的理念,并进行了初步的经济效益分析,论证了在沙漠地区修建此种隧道的可行性。认为开展沙漠中公路隧道的建设不仅可以在沙漠中起到防风固沙的绿化作用,而且有着不可估量的社会经济效益。  相似文献   

C₄ plant species and geographical distribution in relation to climate in the desert vegetation of China     

PeiXi Su  TingTing Xie  ZiJuan Zhou 《寒旱区科学》2011,3(5):0381-0391

Water use efficiency of C₄ plants is higher than that of C₃ plants, and CAM (Crassulaceae Acid Metabolism) plants have the highest water use efficiency. In the desert regions of China, CAM plants are scarce, and C₄ plants, especially C₄ woody plants, have an important position and role in the desert ecosystem. There are 45 species of C₄ woody plants in the desert regions of China, including semi-woody plants, accounting for 6% of the total desert plant species in China, and most of them are concentrated in the families of Chenopodiaceae and Polygonaceae, which are 19 species and 26 species, respectively. The number of C₄ herbaceous plants is 107 species, including 48 monocot species and 59 dicot species. C₄ woody plants mainly inhabit the northwestern arid desert regions of China west of the Helan Mountains. The drought-resistance and drought-tolerance of C₄ herbaceous plants are worse than C₄ woody plants, and C₄ herbaceous plants mainly inhabit areas with shallow groundwater depth and better water conditions in the desert regions, and are widely distributed along the margins of oases. The abundance of C₄ woody plants is closely correlated with drought, but the abundance of C₄ herbaceous plants increases with wet conditions.  相似文献   

The formation of tidal sand waves: Fully three-dimensional versus shallow water approaches     

Paolo Blondeaux  Giovanna Vittori 《Continental Shelf Research》2011,31(9):990-996

Tidal sand waves, also named tidal dunes, are large scale bedforms generated by the growth of perturbations of the sea bottom driven by tidal currents. Indeed, the interaction of an oscillatory tidal current with a bottom waviness gives rise to steady recirculating cells which tend to drag the sediment from the troughs towards the crests of the bottom perturbation. The net motion of the sediment towards the crests is opposed by gravity force and the growth of the perturbation is controlled by a balance between these two effects. In the literature, to determine the conditions which lead to the formation of sand waves and to determine the characteristics of the bedforms generated by this instability mechanism, both fully three-dimensional and shallow water approaches are employed. The shallow water approach is computationally less expensive than the fully three-dimensional one but, in many cases, it might be less accurate. This paper compares the quantitative predictions obtained by means of the two approaches and quantifies the range of the parameters such that the shallow water approximation provides reliable predictions.  相似文献   

New optically stimulated luminescence ages provide evidence of MIS3 and MIS2 eolian activity on Black Mesa, northeastern Arizona, USA     

Amy L. Ellwein  Shannon A. Mahan  Leslie D. McFadden 《Quaternary Research》2011,75(3):395-398

Eolian deposition on the semiarid southern Colorado Plateau has been attributed to episodic aridity during the Quaternary Period. However, OSL ages from three topographically controlled (e.g. falling) dunes on Black Mesa in northeastern Arizona indicate that eolian sediments there were deposited in deep tributary valleys as early as 35–30 ka, with most sand deposited before 20 ka. In contrast, the oldest OSL ages for sand sheets fall within the Pleistocene-Holocene climatic transition (~ 12–8 ka). Thus most eolian sediment accumulated on Black Mesa under climatic conditions that were in general cooler, moister, and more variable than today, not more arid, pointing to a considerable increase in sediment supply.  相似文献   

塔克拉玛干沙漠深部石英砂微结构特征及其环境意义   总被引：4，自引：0，他引：4  

高存海  钱亦兵 《地质论评》1995,41(2):152-158

笔者对采自塔里木盆地腹部钻井岩芯中的石英砂及地表风砂时行了电镜扫描观察，结合沉积岩相和孢粉分析，对塔克拉玛干沙漠第四纪沉积环境做了初步分析，认为深部石英砂形态和结构具有多种外营力作用相互叠加的特征。近地表层显示风－冰川－水流作用的组合形态和结构类型；沉部则主要为水流－冰川－化学为主的组合，随深度增大，化学风化作用增强。地表风成砂不具备成熟的沙漠形态和表面结构，这可能同沙漠本身的年青性有关。  相似文献   

Longitudinal dunes can move sideways   总被引：3，自引：0，他引：3  

Patrick Hesp  Robert Hyde  Virginia Hesp  Qian Zhengyu 《地球表面变化过程与地形》1989,14(5):447-451

Longitudinal dunes occur in all major sand areas in the world. Their dominant mode of migration or extension is considered to be either prevailing- or resultant wind-parallel, the dunes extending downwind via accretion of the terminal nose. In the Qaidam Pendi in Northwest China a series of active longitudinal dunes extend downwind at 5–10 m yr^?1. Internal sedimentary structures examined in the dunes, however, display beds dipping in one direction rather than two opposed directions as is expected. Analysis of aerial photographs confirms that these dunes migrate laterally up to three metres per year, whilst maintaining a symmetrical longitudinal dune morphology.  相似文献   

浑善达克沙区近期气候变化的研究   总被引：4，自引：0，他引：4  

孙安健  刘德松 《南京气象学院学报》1992,15(3):414-421

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荒漠─绿洲交界处辐射差异对比分析     

黄妙芬 《干旱区地理》1996,(3)

辐射过程的研究是水热平衡的基础与出发点．本文通过实验观测，对辐射平衡方程及Rn=Q（1-A）-F0的各项分别进行了荒漠──绿洲间及绿洲不同农田作物间的对比分析．  相似文献   

Nutrient evaluation of some arid range plants in Saudi Arabia     

Ali A. Al-Jaloud  Shaukat A. Chaudhary  Isam I. Bashour  Salahuddin Qureshit  Abdullah Al-Shanghitti 《Journal of Arid Environments》1994,28(4)

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一种确定地表粗糙度的独立方法   总被引：44，自引：2，他引：44       下载免费PDF全文

陈家宜  王介民  光田宁 《大气科学》1993,17(1):21-26

本文提出一种只用单一超声风温仪的平均风速和湍流量测定值确定地表空气动力学粗糙度的方案.该方法经Kansas实验资料验证,效果甚好,由5.66m和22.6m两层超声风温仪数据计算的z_0彼此一致,并且完全符合风速廓线确定的数值.将其用于确定HEIFE实验区平坦戈壁滩的地表粗糙度,1988年和1990年两批数据的估值结果大致相符,z_0分别为1.5×10~(-3)m和1.1×10~(-3)m.由精细风廓线观测发现该地z_0=1.2×10~(-3)m,证实了所建议的方法和z_0估值的可靠性.  相似文献