青藏高原地区总辐射超太阳常数的观测研究

为了研究青藏高原地区 (以拉萨站为代表 )太阳总辐射的变化情况 ,分别使用常规观测站资料和自动观测站资料。常规观测资料使用的是逐日太阳最大总辐射以及出现太阳最大总辐射的时刻。 1993年开始实施的中日亚洲季风研究计划 ,太阳总辐射是每隔 2 0 min采集一次。基于上述资料研究发现有青藏高原太阳总辐射大于太阳常数的反常现象。并对这种反常现象进行了统计 ,得到了一些有意义的结果 ,最后在非局域力学平衡 (NLTE)假设下 ,对出现这种现象提出了可能的解释。     

近20年来黄土高原地区的经济增长时空分异特征

 经济不均衡增长是区域发展的一种常态。分析区域经济增长时空差异及成因,对于认识和加快落后地区的经济发展具有重要的意义。本研究在GIS技术的支持下,对黄土高原地区近20年来以县市为单元的经济增长时空分异特征进行了系统的分析。主要结论有:改革开放以来,黄土高原地区的GDP水平呈现出持续的快速增长态势。近20年来,陕北和内蒙古鄂尔多斯地区增长最为迅速;人均GDP的空间分布整体上呈现出"两高一低"的带状分布格局,且这种格局明显地受到极化增长的扰动和重塑;经济增长表现出显著的极化增长特征,且经济增长极的极化作用与增长极之间地位的调整是同时进行的;与常态化的城市产业集聚推动型经济相比,机遇性的资源开发拉动型经济对人均GDP的拉动速度更快,但可持续性较差。未来,黄土高原地区应走以中心城市带动为主,以能矿产资源开发拉动为辅,两者相互促进,共同带动整个区域经济更快、更好、更可持续地发展的道路。     

近20年黄土高原土地利用/覆被变化特征分析

本文根据黄土高原地区20世纪80年代末、2000年、2008年3期土地利用/覆被空间数据集,计算2个时段（20世纪80年代末-2000年,2000-2008年）土地利用/覆被转类方向及其幅度、土地利用/覆被转类指数、土地利用/覆被状况指数及其变化率,分析黄土高原地区自20世纪80年代末以来土地利用/覆被时空变化特征以及宏观生态状况的变化趋势。结果显示：黄土高原地区近20年来平均土地利用/覆被状况指数为24.07,其中土石山区生态系统综合功能最好,其次为河谷平原区,最差的为农灌区。20世纪80年代末-2000年,黄土高原地区主要土地利用/覆被转类是森林和草地转为耕地,生态级别由高级向低级转移,2000-2008年主要土地利用/覆被转类是耕地转为林地和草地,低覆盖草地转为中高覆盖草地,生态级别由低级向高级转移。近20年来黄土高原地区地覆被状况指数变化以及土地利用/覆被转类指数表明,该区域的宏观生态状况总体上经历了转差（20世纪80年代末-2000年土地利用/覆被转类指数为-1.08）,后转好（2000-2008年土地利用/覆被转类指数为2.66）2个过程。这一变化过程前期受区域气候变化以及人口增长共同驱动,后期则叠加了生态工程的影响。     

Distributed modeling of extraterrestrial solar radiation over the rugged terrains of Pakistan

In Pakistan,the solar analogue has been addressed but its surface geographical parameterization has given least attention.Inappropriate density of stations and their spatial coverage particularly in difficult peripheral national territories,little or no solar radiation data,non-satisfactory sunshine hours data,and low quality of ground observed cloud cover data create a situation in which the spatial modeling of Extraterrestrial Solar Radiation(ESR) and its ground parameterization got sufficient scope.The D...     

Red Clay Sediment in the Central Chinese Loess Plateau and Its Implication for the Uplift of the Tibetan Plateau

Introduction A set of reddish clay-silt-sized sediments named red clay underlying the Quaternary loess-paleosol sequence widely distribute in the Chinese Loess Plateau. The thickness of the red clay sediments ranges from decades of meters to over 100 m (Evan et al.1991,Mo and Derbyshire 1991, SUN et al. 1997&1998, DING et al. 1999, GUO et al. 2001, QIANG et al. 2001). Previous studies show that not only loess-paleosol (e.g.LIU et al.1985,AN et al.1990,DING et al.1992),but also red …     

Spatial-temporal pattern and formation mechanism of county urbanization on the Chinese Loess Plateau

Urbanization is a comprehensive and complex socioeconomic phenomenon that plays an influential role in promoting global socioeconomic development. The Loess Plateau region is an important part of the China's ecological security pattern, and occupies an important position in the implementation of China's new-type urbanization strategy and the realization of the urban dream. The characteristics of the staged changes and regional differentiation of urbanization in the area from 1990 to 2018 were studied with focus on regions and subregions by selecting 341 county-level administrative units on the Chinese Loess Plateau as the research area, and employing partition analysis and geographic detector methods. This revealed the formation mechanism of the spatial differentiation pattern of urbanization on the Loess Plateau. We found that the urbanization of the Loess Plateau,previously in a slow growth phase, entered the accelerated development phase, presenting a macro pattern of high rates of urbanization in central and eastern areas and low rates in western areas. The formation of the regional differentiation patterns of urbanization on the Loess Plateau were the combined results of natural geographical and socioeconomic factors. Among these factors, the interaction of any two factors had a stronger impact on regional urbanization patterns than a single factor, which was specifically manifested as nonlinear or bi-factor enhancement effects. The findings of this paper may provide a theoretical reference and scientific basis for the scientific promotion of healthy urbanization on the Chinese Loess Plateau and the ecologically fragile areas of developing countries around the world.     

Soil erosion differences in paired grassland and forestland catchments on the Chinese Loess Plateau

In this study, two adjacent gauged catchments on the Chinese Loess Plateau were selected, in which one catchment was afforested and one was restored with natural vegetation in 1954. The distributions of soil erosion rates were estimated between 2010 and 2020 with a high spatial resolution of 2 m in the paired catchments based on the Revised Universal Soil Loss Equation model(RUSLE) and Geographic Information Systems(GIS). The results showed that the simulated soil erosion rates in 2010-2020 aver...     

Collapse behavior and microstructural evolution of loess soils from the Loess Plateau of China

Loess soils are characterized by metastable microstructure, high porosity and water-sensitivity. These soils have always been problematic soils and attracted attention from researchers all over the world. In the present study, three loess soils extracted at various depths from the Loess Plateau of China, i.e. Malan (Q₃), upper Lishi (Q₂²) and lower Lishi (Q₂¹) loess soils, were studied. Single oedometer-collapse tests were performed on intact loess specimens to investigate the collapse behavior of three loess soils. The microstructure and chemical composition of each loess before and after collapse test were characterized using scanning electron microscopy (i.e. SEM) and energy dispersive spectroscopy (i.e. EDS) techniques. The microstructural evolution due to wetting collapse was interpreted qualitatively and quantitatively in terms of the pore morphology properties. The results suggest that: ① the collapse potential of each loess may rise again after a round of rise and drop, which could be failure of the new-developed stable structure under quite high vertical pressure. It implies that loess may collapse even if it has collapsed. ② Q₃, Q₂² and Q₂¹ loess have different types of microstructure, namely, granule, aggregate and matrix type of microstructure, respectively. ③ The microstructural evolution due to loading and wetting is observed from a granule type to an aggregate type and finally to a matrix type of structure. The variations in distributions of pore morphology properties indicate that collapse leads to a transformation of large-sized pores into small-sized pores, re-orientation and remolding of soil pores due to particle rearrangement. ④ A porous structure is essential for loess collapse; however, the non-water-stability of bonding agents promotes the occurrence of collapse under the coupling effect of loading and wetting.     

基于DEM的黄土地貌类型提取与制图——以黄土高原丘陵沟壑实验样区为例

以陕北绥德县刘家沟流域为实验样区 ,从地貌成因、形态和土地利用角度出发 ,分析了黄土高原丘陵沟壑区 3种典型地貌类型的区域特征 ;以不同地貌类型的区域特征为基础 ,在地理信息系统平台软件 Arc View的支持下 ,利用数字高程模型 (DEM)自动提取黄土丘陵区 3种基本地貌类型的方法和技术。研究分析结果证明 :利用 DEM自动提取地貌类型是一种快速、高效的技术方法 ,对指导退耕还林、防治水土流失和进行土地利用动态监测都具有重要意义。     

HUMAN IMPACTS ON THE ECOLOGICAL ENVIRONMENT AND MODERN URBAN CLIMATE CHANGE IN THE LOESS PLATEAU

The influence of human activities on environment and climate change is the most conspicuous problem of the Loess Plateau, and it may be divided into two aspects: firstly, the excessive utilization of land by the human race causes the destruction of vegetation, and consequently large expanse of land is under desertification and the characteristics of the ground surface and the water and heat exchange on the ground surface have changed; secondly, the use of coal by industries produces a huge amount of carbon dioxide and trace elements, which enter into the atmosphere to cause air pollution.Data of 1951-1990 are collected from 69 meteorological stations on the Loess Plateau. After analysis, the decadal variations of temperature and rainfall in the last 40 years are obtained as follows: (1) In the arid zone of the north- west of the Loess Plateau, the increase in temperature is the largest. For the past 40 years, the annual mean temperature has increased 0.7-1.0 ℃ . In the semiarid zone of the middle part     

Vegetation Restoration in Response to Climatic and Anthropogenic Changes in the Loess Plateau,China

A thorough understanding of the vegetation succession in relation to both climatic changes and anthropogenic activities is vital for the formulation of adaptation strategies that address potential ecosystem challenges. Various climatic factors such as temperature, precipitation, and solar radiation, as well as anthropogenic factors such as ecological engineering and population migration, will affect the conditions for vegetation. However, the relationships among various factors remain unclear and the response of vegetation to climate change and anthropogenic activities in the Loess Plateau of China has not been well established. This study investigated the spatio-temporal characteristics and relationships between vegetation coverage and climatic factors in the Loess Plateau for the period of 1985–2015. Further analysis separated the anthropogenic and climatic factors on vegetation succession based on residual analysis. The results showed that the normalized difference vegetation index(NDVI) followed a significant upward trend with annual change rates of 0.15% during 1985–2015. The trend of human-induced NDVI increase was consistent with the spatial distribution of increasing forest areas in the eastern part of the Loess Plateau. Eco-restoration projects were the main driving factors that promoted vegetation coverage on the Loess Plateau. Furthermore, these results demonstrated that migrants to cities in the Loess Plateau could relieve ecological pressures and promote vegetation restoration. Therefore, the government should strive to increase population mobility and restore vegetation to sustain this particularly fragile ecological environment.     

黄土高原沟谷地貌发育演化研究进展与展望

黄土沟谷是黄土地貌中最有活力、最具变化、最富特色的对象单元,黄土高原千沟万壑的地貌形态以及触目惊心的侵蚀状态也让区域内沟谷地貌的形成、发育及演化问题成为研究中焦点及前沿性科学问题。近年来,诸多学者采用地学测年法、特征表达法、监测模拟法力图实现对黄土沟谷发育演化进程中“过去-现代-未来”的科学认知。这些研究在相当程度上丰富了黄土沟谷发育过程的认知。本文梳理了黄土高原沟谷地貌演化相关研究的现状,并从黄土高原地貌演化、黄土沟谷发育、基于DEM的沟谷信息提取与表达等研究进行了系统的回顾、梳理与分析。此外,本文提出“黄土沟道剖面群组”概念与方法,试图从新的视角审视黄土沟谷地貌发育演化过程。沟道剖面在黄土沟谷发育演化进程中传递物质能量和累积地形动力,并通过径流节点的串联实现剖面群的连接与组合,形成独特的剖面“群组”模式;该沟道剖面群组是集黄土沟谷地貌特征与过程于一体的综合信息集成体,其三维空间结构是对黄土沟谷地貌发育演化的高度抽象与映射,并可望进一步丰富黄土高原数字地形分析理论与方法体系,为黄土高原黄土地貌成因机理与空间分异格局带来创新的认识。     

Distribution,failure risk and reinforcement necessity of check-dams on the Loess Plateau: a review

Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau.Based on the data of check-dams from 1950 to 2014,our study roundly analyzed the regional distribution,function and the problems of check-dams on the Loess Plateau.A total of 17,094 check-dams with a storage capacity of over 100,000 m³ and an average density of 0.027 counts km^-2 were installed on the Loess Plateau.Check-dams’densities varied greatly in the Qinghai Province,Gansu Province,Ningxia Hui Autonomous Region,Inner Mongolia Autonomous Region,Shaanxi Province,Shanxi Province and Henan Province.The highest density of check-dams reached 0.088 counts km^-2 in Shaanxi Province,whereas the lowest density of check-dams was only 0.005 counts km^-2 in Qinghai Province.However,after decades of operation,3025 large check-dams and 2257 medium check dams are dangerous and have security risks,which are seriously threatening downstream safety.The dangerous rate of checkdams is high.Specifically,the check-dams in Shanxi and Qinghai Province have the highest dangerous rates,with both exceeding 53%.Therefore,there is an urgent need for carrying out reinforcement of the dangerous check-dams.The results are helpful to policymakers to extend and develop check-dams.     

Characteristics and influencing factors of proximity distance index on the northern Shaanxi Loess Plateau in China

Topographic feature points and lines are the framework of topography, and their spatial distance relationship is an breakthrough in the study of topographical geometry, internal structure and development level. Proximity distance(PD) is an indicator to describe the distance between the gully source point(GSP) and the watershed boundary. In the upstream catchment area, PDs can be expressed by the streamline proximity distance(SPD), as well as by the horizontal proximity distance(HPD) and the vertical proximity distance(VPD) in the horizontal and vertical dimensions, respectively. The series of indicators(e.g., SPD, HPD and VPD) are important for quantifying the geomorphological development process of a loess basin because of the headward erosion of loess gullies. In this study, the digital elevation model data with 5 m resolution and a digital topographic analysis method are used for the statistical analyses of the SPD, VPD and HPD in 50 sample areas of 6 geomorphic types in the Loess Plateau of northern Shaanxi. The spatial characteristics and the influencing factors are also analysed. Results show that: 1) Central tendencies for the HPDs and the VPDs for the whole study area and the six typical loess landforms are evident. 2) Spatial patterns of the HPDs and the VPDs exhibit evident trends and zonal distributions over the whole study area. 3) The HPDs have a strong positive correlation with gully density(GD) and hypsometric integral. The VPDs also correlates with GD to an extent. Vegetation cover, mean annual precipitation and loess thickness have stronger effects on the VPD than on the HPD.     

Glacier extent changes and possible causes in the Hala Lake Basin of Qinghai-Tibet Plateau

Glacier is a common sensitivity indicator of environmental and global climate change.Examining the relationship between glacier area and climate change will help reveal glacier change mechanisms and future trends. Glacier changes are also of great significance to the regulation of regional water resources. This study selected the Hala Lake Basin in the northeastern Qinhai-Tibet Plateau as a study area, and examined the relationships between the temporal and spatial change of glaciers in the northeastern Qinghai-Tibet Plateau and climate change based on remote sensing imagery,climatological data, and topographic data during the past 30 years. Results showed that glacier area in the Hala Lake basin fluctuated and decreased from106.24 km~2 in 1986 to 78.84 km~2 in 2015, with a decreasing rate of 0.94 km~2·yr~(-1). The number of glacier patches, mean patch area, and largest patch index all decreased from 1986 to 2015, while the splitting index increased from 1986 to 2015,indicating that the landscape fragmentation of glacier in the Hala Lake Basin was increasing significantly during the study period. Glacier area change was mainly concentrated in the slopes 25° with an altitude of 4500-5000 m, and the retreating rate of glacier of sunny slope was obviously higher than that of shady slope. Geometric center of glacier in the basin moved from southwest to northeast towards high altitude. Results of the response of glacier extent to climate change showed that temperature was the dominant factor affecting glacier area dynamic change in the Hala Lake Basin. It is predicted that in future several years, the glacier area will decrease and fragment continually as a result of global warming on the Tibetan Plateau.     

Stability analysis unit and spatial distribution pattern of the terrain texture in the northern Shaanxi Loess Plateau

Terrain texture analysis is an important method of digital terrain analysis in quantitative geomorphological research and in the exploration of the spatial heterogeneity and autocorrelation of terrain features. However, a major issue often neglected in previous studies is the calculation unit of the terrain texture, that is, the stability analysis unit. As the test size increases, the derived terrain textures become increasingly similar so that their differences can be ignored. The test size of terrain texture is defined as the stability analysis unit. This study randomly selected 48 areas within the Loess Plateau in northern Shaanxi in China as the study sites and used the gray level co-occurrence matrix to calculate the terrain texture. The stability analysis unit of the terrain texture was then extracted, and its spatial distribution pattern in the Loess Plateau was studiedusing spatial interpolation method. Four terrain texture metrics, i.e., homogeneity, energy, correlation, and contrast, were extracted on the basis of the stability analysis unit, and the spatial variation patterns of these parameters were studied. Results showed that the spatial distribution pattern and the terrain texture metrics reflected a trend of high–low–high from north to south, which correlated with the spatial distribution of the landforms at the Loess Plateau. In addition, the terrain texture measures was significantly correlated with the terrain factors of gully density and slope, and this relationship showed that terrain texture measures based on the stability analysis unit could reflect the basic characteristics of terrain morphology. The stability analysis unit provided a reasonable analytical scale for terrain texture analysis and could be used as a measure of the regional topography to accurately describe basic terrain characteristics.     

黄土高原丘陵沟壑区切沟侵蚀与地形关系分析——以纸坊沟流域为例

沟蚀是土壤侵蚀研究的主要内容之一,地形地貌是沟蚀的一个重要影响因子。本文以安塞纸坊沟流域作为研究区域,选择土地利用方式、土壤类型、坡度坡长因子、平面曲率、坡向和地形湿度指数6个因子,通过因子内切沟所占比重/整个研究区切沟所占比重计算各个因子的权重值,通过空间叠加分析土壤侵蚀敏感性,并通过重分类的方法把土壤侵蚀敏感性分为基本无侵蚀、轻度侵蚀、中度侵蚀、强度侵蚀、剧烈侵蚀5个等级,来研究切沟侵蚀与地形的关系。结果表明：切沟多发生在坡度坡长较大、地表湿度较高的林草地区域和更容易发生侵蚀的黄绵土区域,并且多分布在阴坡的凹面;对比分析切沟侵蚀和土壤侵蚀敏感性,切沟大多分布在中等侵蚀敏感性以上的区域,约占总切沟的90%;实验权重值对验证区冲沟的响应精度为82.43%（中度侵蚀及其以后阶段）,与实际值90.53%相差不大,说明此种方法对黄土丘陵沟壑区具有一定适用性,对黄土丘陵沟壑区水土保持工作有重要意义。     

黄土高原地貌形态图谱三维符号指标体系与应用

长期以来,地貌学界和制图学界一般是采用文字、地图和图像等方式来描述黄土高原独特的地貌形态,故往往不够形象,缺乏系统性。采用地学信息图谱和三维可视化的方法,对挖掘揭示黄土高原地貌形态特征规律是一个有效的方法。黄土高原地貌形态图谱三维符号的指标体系,是将地貌学家和制图学家对黄土高原正负地貌类型的认知结果经过系统化、标准化和科学化的归纳和提炼,从中提取出的描述黄土高原地貌三维特征的参数集合。既是对黄土高原地貌形态图谱三维立体特征的充分概括,又是三维形式建模表达的参考和依据。根据黄土高原地貌类型的分类和侵蚀特征规律,该体系分为正地貌形态指标体系、负地貌形态指标体系和坡度一侵蚀特征谱系描述指标,采用定性和定量相结合的方法来制定指标体系的具体参数。最后通过实例来验证指标体系在构造三维符号时的应用。细致精确的描述单个地貌类型的三维形态,将有助于对黄土高原地貌特征的认识和研究,为水土保持和生态环境建设提供帮助,同时也为其他地貌类型的信息图谱研究提供借鉴。     

Vegetation Mapping for Regional Ecological Research and Management: A Case of the Loess Plateau in China

Vegetation maps are fundamental for regional-scale ecological research. However, information is often not sufficiently up to date for such research. The Loess Plateau is a key area for vegetation restoration projects and a suitable area for regional ecological research. To carry out regional vegetation mapping based on the principles of hierarchical classification, object-oriented methods, visual interpretation, and accuracy assessment, this study integrated land cover, high-resolution remote sensing images, background environmental data, bioclimate zoning data, and field survey data from the Loess Plateau. To further clarify the implications of vegetation mapping, we compared the deviation of the 2015 vegetation map of the Loess Plateau(VMLP) and the widely used vegetation map of China(VMC)(1 : 1 000 000) for the expressed vegetation information and the evaluation of ecosystem services. The results indicated that 1) the vegetation of the Loess Plateau could be divided into 9 vegetation type groups and 18 vegetation types with classification accuracies of 87.76% and 83.97%, respectively; 2) the distribution of vegetation had obvious zonal regularity; 3) a deviation of 29.56 × 10~4 km~2 occurred when the vegetation coverage area was quantified with the VMC; 4) the vegetation classification accuracy affected the ecosystem service assessment, the total water yield of the Loess Plateau calculated by the VMC and other required parameters was overestimated by 2.2 × 10~6 mm in 2015. Because vegetation mapping is a basic and important activity, that requires greater attention, this study provides supporting data for subsequent multivariate vegetation mapping and vegetation management for conservation and restoration.