火星Kaiser陨石坑新月形沙丘近表层风况特征

风沙地貌的形态和分布能够较好地反映区域风况,而沙波纹作为一种小尺度的风沙地貌类型,可以很好地指示现代风况下沙丘近表层的流场状况。文中利用HIRISE影像监测了火星南部Kaiser陨石坑内新月形沙丘表层沙波纹的形态特征,并以此探讨分析了沙丘近表层的气流场特征。结果表明:(1)沙波纹的脊线长度主要分布在100-300m之间,平均长度为190.3m;波长主要分布在2-5m之间,平均波长为3.1m,且基本符合正态分布。(2)三处样地沙波纹的主要走向分别为NE-SW、N-S和NW-SE,与沙丘脊线走向呈近似90°的夹角。(3)沙丘近表层气流的走向主要为NW-SE、W-E和SW-NE,并由此推断陨石坑内沙丘主要受到自西向东气流到控制,在遭遇地形影像后又向西发生了折返。上述研究表明沙丘形态及其分布的区域差异性是在复杂的风沙环境下形成的,沙波纹可用作沙丘近表层风况特征研究的代用指标。     

中国北方典型流域河道与沙丘空间格局及其动态变化

风水交互作用是干旱区常见的地貌现象和重要的地表过程,河谷沙丘是发育在河谷环境中迭置于河流地貌之上,受风水两相作用的一种特殊类型的风沙地貌。本文选择不同气候区克里雅河、毛布拉格孔兑、西拉木伦河3条河流作为研究区,分析其典型河段近30 a河道与沙丘空间格局及其变化,结论表明:自西向东3个流域空间格局分别为河道穿越流沙区、河道穿越流沙区与沙丘斑块镶嵌河道二者兼有、沙丘斑块镶嵌河道3种格局;同一气候区不同河段具有不同的空间格局动态变化特征:河道穿越流沙区的格局为上中游河段不稳定型、中下游平衡型、尾闾段的稳定型三种类型;沙丘斑块镶嵌河道的空间格局均以支流入河口的动荡型以及主河道"短命沙丘"变化比较突出。气候因素影响风水交互作用的强弱和方式,从而形成不同河岸风沙地貌格局及其变化特征。     

东昆仑山区沙漠初步研究

一、沙漠分布库木库里盆地中分布着我国海拔最高的五小片沙漠,总面积为3054平方公里,占盆地面积的6.78％。各种沙丘形态组成本区内具有特色的地貌景观,其沙漠的分布独具特点:新月形沙丘链、金字塔沙丘等分布在两山夹持的谷地中,而半固定沙堆和平沙地等,则分布在开阔的湖积平原和开阔谷地上,可见沙丘类型的分布是受风力和下伏地形地貌制约的。根据沙丘分布的集中情况,可将其分成五片小沙漠(见表1):     

最近10年来新疆风沙地貌研究进展

最新研究表明,塔克拉玛干沙漠风沙活动与气温变化呈现"风热同步"现象,虽然其风况类型多样,但整个沙漠处于低风能环境。不同沙丘部位上风沙流输沙量的对数与高度之间表现为线性关系。当气流与沙丘走向斜交时,两侧相同部位输沙率的差异不大,这是线形沙丘保持其动力形态平衡的主要原因之一。古尔班通古特沙漠也处于复合型低能风环境之中,冬季积雪和冻土对沙漠地表形成有利的保护,有效植被覆盖和生物结皮是沙面整体处于稳定状态的重要因素,风沙活动仅存在于沙垄顶部和两坡上部。沙漠中生物结皮发育、种类丰富,其类型和分布具有明显的景观异质性特征。天山北坡和昆仑山北坡的黄土研究揭示,新疆两大沙漠从中更新世以来出现明显的干旱化,沙漠逐步扩大至今天规模。此外,塔里木沙漠公路和古尔班通古特沙漠输水明渠沿线的风沙危害具有明显的时空分异特点。因此,根据工程设施所处地形与地貌部位,可定性判断风沙危害类型与强度,进而确定防治方案和措施。今后新疆风沙地貌学研究应注重研究领域的拓展、研究方法的突破和实验手段的创新3个方面。     

流动沙丘区公路路基风沙流场数值模拟及路面沙害形成机制

基于CFD(Computational Fluid Dynamics)数值模拟,以青海省中灶火省道303公路为研究区域,对流动沙丘区公路路基风沙流场进行了模拟分析,揭示了流动沙丘区路面沙害的形成机制,以期为流动沙丘区路面沙害的防治提供理论依据。数值模拟结果表明:当气流经过流动沙丘和路基时,气流速度产生分区;当存在流动沙丘时,路基周边的减速区范围明显增大,路基坡面和背风坡全部处于气流低速区的范围,沙丘高度以上,在沙丘顶部气流速度急剧增大,受障碍物自身形状的影响,风速变化由"Ω"型分布变为"M"型分布。当沙丘表面的原有防护体系疏于维护、更新,沙粒在沙丘附近大量堆积,沙丘会慢慢沿主风向移动,成为沙源,掩埋路基而形成沙害。数值模拟结果与现场实际相吻合,证实了数值模拟的准确性。对于流动沙丘区公路的沙害防治,应详细考察当地的地貌形态及风沙流运动规律,定期检查维护原有防护体系,及时清理积沙,既要阻止风沙流对沙丘进行沙源供给,又要防止沙丘本身成为沙源。     

塔克拉玛干沙漠腹地高大复杂纵向沙垄区简单横向沙丘形态特征的空间变异

为了探讨小尺度风沙地貌形态的空间变异过程,对塔克拉玛干沙漠腹地高大复杂纵向沙垄横断面上简单横向沙丘形态特征进行了研究。沙丘形态野外测量采用RTK(real-tim e k inem atic)技术,并通过南方测绘软件(South Survey)量算形态特征参数。结果表明:简单横向沙丘形态特征参数及其相互关系具有空间变异性。在8个地貌部位之间,沙丘形态特征参数(不包括迎风坡度)存在显著性差异,主要体现在:垄顶、沙垄背风坡、其他地貌部位(包括垄间地和沙垄迎风坡)三者之间的差异。地貌部位、输沙风强度以及沙丘活动强度是驱动沙丘形态空间变异的因素。沙丘高度与翼展度余弦有负对数关系,发育指数与高度、迎风坡度成负线性相关,这些相关性的显著程度在垄顶、背风坡较高,在垄间和迎风坡较低。     

科尔沁沙地景观梯度带上植被的空间分布格局研究

根据 1 997— 1 998年对科尔沁沙地沙丘植被的实地调查 ,本文依据植物地理学、植物生态学的方法 ,对不同景观梯度带上沙丘植被的植物组成及其重要值等进行了分析 ,从而研究出该地区现阶段在风力水力侵蚀胁迫下的退化草原植被的空间分布格局 ,同时也说明植被的分布与大气降水所制约的水分梯度和风力侵蚀发展的沙漠化梯度有直接的关系。     

基于SRTM-DEM和TM的流动沙丘提取方法研究

以塔克拉玛干沙漠的流动沙丘地貌为例,进行数字地貌形态提取方法研究。首先,利用高精度Srtm-DEM数据派生出坡度和起伏度两个地形因子数据,并参考坡度和起伏度的分类指标,实现沙地和沙丘边界线的自动提取,将风成地貌按照形态特征区分出沙地和沙丘两种地貌类型。其次,利用数学分析方法,根据斑块指数值的大小初步确定复合流动沙丘的类型。最后,基于高空间分辨率的遥感影像的色调、纹理、结构等特征,建立典型流动沙丘地貌特征的遥感影像特征图谱,依据遥感图谱进一步确定复合流动沙丘的类型,实现典型复合流动沙丘地貌形态和成因特征的计算机智能化提取方法。研究结果表明:该方法目前可以实现流动沙丘中的复合型链垄状沙丘、复合型沙垄、穹状沙丘和蜂窝状沙丘的智能化提取。     

库姆塔格沙漠南部的风积地貌特征

通过考察结果和TM影像解译,库姆塔格沙漠的东南分布高大的沙山,沙丘形态复杂;南部和西南缘分布有多条南北走向的荒漠沟谷,两岸分布沙垄,高18~65m,垄脊点(金字塔型)线交错,沙垄走向与沟的走向一致,阶地上覆盖一层深色矿物组成的砂砾(粒径3~1mm)。沙漠的中心区域,孤立的新月型沙丘、沙丘链占优势。下伏地形强烈影响着库姆塔格沙漠的风沙地貌形态。沙漠南部的低山、阿尔金山及其山前洪积沟谷形成的沟谷效应,塑造了沙漠南部复杂的地貌形态。沙漠沙丘砂的粒径由南向沙漠中心减小,0.25~0.05mm细砂占80%左右。     

海岸风沙运动观测与模拟的研究与进展

海岸风沙运动的观测与模拟研究是海岸风沙地貌等海岸风沙问题研究的基础与核心。本文依据 1 980— 1 999年间的国内外研究文献 ,较为详尽地回顾近 2 0年来国内外尤其是国外的海岸风沙运动观测与模拟研究 ,综述了包括在海岸沙丘表面气流运动与风沙流结构观测、海岸风沙运动速率观测以及海岸风沙运动方程的验证、修正与建立等方面的主要进展、成果与问题     

面向子流域单元的典型黄土地貌分类研究

基于格网DEM的数字地貌形态类型自动划分是当前地貌研究的热点。根据基本分析单元的粒度大小,可将现有的分类方法划分为以栅格为分析单元和不规则坡面多边形为分析单元。然而,上述2种方法都无可避免地存在分类结果中地貌实体不完整性的问题。本文将分析单元提升至小流域级别,提出面向"细胞"级的微小尺度的子流域为分析对象的分类思想,利用GIS空间分析方法,构建子流域地理属性数据库,依据研究区已有的地貌资料,遴选出高程、起伏度、平均坡度、坡谱偏度4个核心分类指标,采用层次分类法,设定相应的地形因子阈值,将陕西省铜川市耀州区划分为:河漫滩、黄土残塬、黄土台塬、陡坡冲沟、墚峁状丘陵沟壑、石质小起伏平缓中山、石质小起伏陡峭中山以及水域等8大类型。分类结果最大程度保证了地貌实体的相对完整性,与用GPS进行的实地采样观测结果对比分析表明,该方案的分类精度达到88. 19%,可望成为基于面向子流域单元进行数字地貌分类研究的有益探索。     

Wind regimes and associated sand dune types in the hinterland of the Badain Jaran Desert,China

Wind controls the formation and development of sand dunes. Therefore, understanding the wind regimes is necessary in sand dune research. In this study, we combined the wind data from 2017 to 2019 at four meteorological stations (Cherigele and Wuertabulage stations in the lake basins, and Yikeri and Sumujilin stations on the top of sand dunes) in the hinterland of the Badain Jaran Desert in China, with high resolution Google Earth images to analyze the correlation between the wind energy environments and dune morphology. The results of data analysis indicated that both the wind direction and sand drift intensity exhibited notable spatial and temporal variations. The highest level of wind activity was observed in spring. Northwesterly and northeasterly winds were the dominant in the Badain Jaran Desert. At the Cherigele, Wuertabulage, and Yikeri stations, the drift potential (DP) was below 200.00 vector units (VU). The wind energy environments in most areas could be classified as low-energy environments. The resultant drift direction differed at different stations and in different seasons, but the overall direction was mainly the southeast. The resultant drift potential (RDP)/DP ratio was greater than 0.30 in most parts of the study area, suggesting that the wind regimes mainly exhibited unimodal or bimodal characteristics. Differences between the thermodynamic properties and the unique landscape settings of lakes and sand dunes could alter the local circulation and intensify the complexity of the wind regimes. The wind regimes were weaker in the lake basins than on the top of sand dunes. Transverse dunes were the most dominant types of sand dunes in the study area, and the wind regimes at most stations were consistent with sand dune types. Wind was thus the main dynamic factor affecting the formation of sand dunes in the Badain Jaran Desert BJD. The results of this study are important for understanding the relationship between the wind regimes and aeolian landforms of the dune field in the deserts.     

Sand source and formation mechanism of riverine sand dunes: a case study in Xiangshui River,China

Riverine sand dunes develop as a result of fluvial-aeolian interactions. The primarily barchan dune chains along the Xiangshui River (a branch of the Xar Moron River in the western part of the Horqin Sandy Land of China) form a typical riverine dune field. We collected a series of samples from the riverine sand dunes parallel to the direction of the prevailing wind and investigated the sand sources and formation mechanisms of these dunes by determining the grain size, heavy mineral content and optically stimulated luminescence (OSL) of the samples. The sand of the near-river dunes was coarser than the sand of the dunes distant from the river, indicating that coarse sand of the valley mainly deposited on near-river dunes. The heavy mineral analysis suggested that wind-sand activity levels were intense on the upwind dunes, but relatively weak on the downwind dunes. This indicated that the sand sources for the near-river dunes were more abundant than those of the distant dunes. Our OSL analysis of samples suggested that the deposition rates on dunes near the river were greater than the deposition rates on dunes distant from the river. The development of dunes along the river indicated that the river played an important role in dune formation and development. In addition, airflow fluctuation and the formation of the waveform dunes had a type of feedback relationship. Grain size, heavy mineral and OSL analyses are widely used methods in wind-sand research. Sand dune grain size characteristics reflect the effects of airflow on the transport and separation of sand materials, as well as the physical characteristics of the sand sources. Heavy mineral characteristics are often used to investigate the relationships between sediments and sand sources. OSL indicates dune age, revealing formation of dunes. Therefore, it is useful to explore dune sand sources, as well as the mechanisms underlying dune formation, by determining grain size, heavy mineral content and OSL. This study investigated the sand sources of riverine dunes and provided new information about riverine dune formation and development.     

黄土耕作坡面微地形面积高程积分计算及特征研究

面积高程积分(Hypsometric Integral,HI)是定量表征地形发育阶段及侵蚀趋势的重要指标。通过90mm/h雨强下4个典型坡度的人工模拟分段降雨试验,在三维激光扫描的基础上,利用点云数据生成DEM,对微地形坡面HI值的3种计算方法及其变化特征进行了分析,并根据细沟河网格网的HI值进行了验证。结果表明:1)HI方法可用于微地形坡面侵蚀发育的定量表征,HI值介于0.50-0.59之间。在不同坡度条件下,细沟出现之前坡面侵蚀量逐渐增加且HI总体呈现递减趋势,而细沟出现后侵蚀量在细沟中有所堆积且HI值有一定回增。2)河网格网HI值介于0.45±0.11之间。随着坡度的增加,HI值总体上表现出增加的趋势,潜在侵蚀能力有增大的趋势且侵蚀量和坡度之间存在一定的转折关系。3)对比3种不同HI计算精度来看,坡面HI与格网HI之间的RMSE和SAE值差别并不明显,但总体均表现为积分曲线法的计算精度要略优于体积比例法和起伏比法。研究结果对于丰富微地形尺度下HI的计算,深入认识坡面侵蚀发育过程及其机理具有重要的参考价值。     

Coastal environment of the past millennium recorded by a coastal dune in Fujian,China

Coastal dune is a common aeolian geomorphology in a sandy coast,which records the evolution process of the aeolian landscape system and reflects the complex interaction among land surface,atmosphere and ocean.Coast is a sensitive area to global climate change.Restricted by chronology,most previous researches in China focused only on the cause of formation of coastal dunes.In recent years,the development of optically stimulated luminescence (OSL) dating provides a good method and acts as a carrier for coastal dunes to paleoclimate and paleoenvironmental studies.In this study,we selected an aeolian dune at the Anshan archaeological site,Fujian,China as the research object based on field observations.For determining their sedimentary stages and the primary influencing factors,we used the OSL dating method to construct a chronological framework for the aeolian dune.In addition,the sizes of grains were analyzed for identifying factors influencing the winter monsoon during the Medieval Warm Period (MWP) and the Little Ice Age (LIA) in this area.The results showed that the deposition of the aeolian dune was closely related to variations in the winter monsoon intensity.The changes of the winter monsoon were similar to the tendency of the East Asian winter monsoon,although there were several sub-fluctuations.From an overall perspective,the winter monsoon was strengthened during the MWP (1050–1300) .The results of a power spectrum analysis showed that the intensity of the East Asian winter monsoon is correlated with sunspot activity.     

Morphological characteristics and dynamic changes of seif dunes in the eastern margin of the Kumtagh Desert,China

The seif dune field over the gravel desert surface in the eastern margin of the Kumtagh Desert is a valuable experimental site for the observation of dune formation and dynamics. We used high-resolution remote sensing and station observation approaches, combined with wind and grain size data, to study the characteristics of the aeolian environment and the morphologies of and dynamic changes in seif dunes. We observed the ratio of the resultant drift potential (RDP) to the drift potential (DP), which was 0.37, associated with an obtuse bimodal wind regime. The drift potentials in the west-northwest (WNW) and east-northeast (ENE) directions were dominant, and the angle between the two primary DP directions was 135.00°. The dune orientations ranged from 168.75°-213.75°, which were parallel to the resultant drift direction (186.15°). The dune lengths ranged from 51.68 to 1932.11 m with a mean value of 344.91 m. The spacings of the dunes ranged from 32.34 to 319.77 m with a mean value of 93.39 m. The mean grain size of the sediments became finer, and the sorting became better from upwind tail to downwind tip, which indicated that the sediment of the seif dunes in the study region may be transported from northward to southward. The rate of increase in the length, the mean longitudinal migration rate of the dune tail, and the mean longitudinal extension rate of the dune tip (also called elongation rate) were 4.93, 4.63, and 9.55 m/a, respectively. The mean lateral migration vector of the seif dunes was approximately 0.11 m/a towards the west (-0.11 m/a), while the mean amplitude of lateral migration was 0.53 m/a, ignoring the direction of lateral migration. We found that the seif dune field formed first beside seasonal rivers, which can provide sediment, and then expanded downwind.     

麻扎塔格山对其南北侧风沙地貌的影响

麻扎塔格山位于塔克拉玛干沙漠腹地的和田河以西,北纬38°30′—38°40′,东经79°43′—80°48′,东西长120公里,南北宽2—4公里,高出山南平原200—300米。它的西侧是与麻扎塔格山结构、构造相似的古董山、罗斯塔格山,这一几乎连续的隆起把和田河西部的沙漠分为南北两部分。麻扎塔格山是由中上石炭系、二迭系和老第三系石灰岩、红色砂岩所组成。在该地区出露的老第三系乌拉根——卡拉塔尔组地层,中下部浅灰黄色钙质砂泥岩中夹有介壳层,含有贝氏牡蛎化石,在齐姆根组和阿尔塔什组的灰绿色泥岩、白云岩地层中含有双     

Geomorphologic patterns of dune networks in the Tengger Desert,China

Dune networks are widely distributed in the world's deserts,which include primary ridges and secondary ridges.However,they have not been sufficiently studied in a systematic manner and their origins and spatial and morphological characteristics remain unclear.To provide information on the geomorphology of dune networks,we analyze the software geomorphologic patterns of the dune networks in China's Tengger Desert using matrix and laboratory to process remote-sensing images.Based on analysis of image features and their layout in a topographic map,we identify two types of dune networks (square and rectangular dune networks) with different size and morphological structures in the Tengger Desert.Four important geomorphic pattern parameters,ridge length,spacing,orientation and defect density,are analyzed.The length of primary ridges of dune networks decreases from northwest of the desert to the southeast,resulting an increasing spacing and a transition from rectangular dune networks to square dune networks.Wind regime and sediment supply are responsible for the variation in pattern parameters.We use the spacing and defect density data to estimate the construction time of dune networks and found that the dune networks in the Tengger Desert formed since about 1.3 ka BP.     

绿洲荒漠化及其评价指标体系的初步探讨

针对目前荒漠化评价指标体系中存在的问题，在大量前人工作的基础上，选取位于极端干旱区的民勤绿洲作为研究样区，在对绿洲荒漠化特点及其发生的自然与人为原因分析的基础上，对绿洲沙质荒漠化发生的边界范围，荒漠化评价指标选取原则等问题进行了探讨，最后从灌丛沙堆发育程度，土壤、植被、人为因素，地貌形态及其发育程度等5个方面，提出了一套以地面工作为基础的绿洲沙质荒漠化评价指标体系。