中国沙漠化程度判定与分区初步研究   总被引：15，自引：2，他引：13  

董玉祥  陈克龙 《中国沙漠》1995,15(2):170-174

依据沙漠化发生发展的地域分异规律,遵循综合性、主导性和县域完整性原则,制定了包括沙漠化土地占地率等6个评价指标的沙漠化程度评价指标体系,建立了定量评价模型,利用最新数据对我国的沙漠化现有程度进行了程度判定与分区,共划分出8个轻度区、7个中度区和5个重度区。  相似文献   

中国降水分区   总被引：4，自引：0，他引：4       下载免费PDF全文

CHEN Li-Juan  CHEN De-Liang  WANG Hui-Jun  YAN Jing-Hui 《大气和海洋科学快报》2009,2(5):301-307

Precipitation regimes of China were mapped by using empirical orthogonal function (EOF) analysis with orthogonal rotation based on normalized monthly mean precipitation data at 400 stations from 1961 to 2006.The regional boundaries were defined with the maximum-loading approach.The results identified 13 consistent and contiguous precipitation regions with distinct regional variations in China that are expected to reflect dominant regional patterns focusing on seasonal and interannual precipitation variations.The precipitation regionalization is operationally useful for seasonal and interannual climate predictions.  相似文献   

主体功能区划可利用土地资源指标项及其算法   总被引：8，自引：4，他引：4  

徐勇  汤青  樊杰  刘若梅  周艺 《地理研究》2010,29(7):1222-1231

测算和评价可利用土地资源(即后备适宜建设用地潜力)是开展主体功能区划的关键基础工作之一。在重点阐述主体功能区划可利用土地资源指标项涵义、功能、重要因素参数选择以及算法和技术流程的基础上,借助GIS空间分析技术,利用数字地形高程图(DEM)、2000年TM遥感影像解译土地利用图、县级行政区划图和国土部门土地利用变更数据,测算和评价了2005年我国可利用土地资源的数量和空间分布特征。研究结果表明:2005年我国可用于建设用地的可利用土地资源面积约28.54×10⁴km²,占全国陆地国土总面积的3.01％;全国人均可利用土地资源面积为0.34亩/人,其空间分布的基本特点是高值区相对集中于东北、华北北部、西北以及黄河中游地区,低值区成片集中于青藏高原和中、东部人口密集地区。  相似文献   

Regional frequency analysis of daily rainfall extremes using L-moments approach     

《Atmósfera》2014,27(4):411-427

Daily extreme precipitation values are among environmental events with the most disastrous consequences for human society. Information on the magnitudes and frequencies of extreme precipitations is essential for sustainable water resources management, planning for weather-related emergencies, and design of hydraulic structures. In the present study, regional frequency analysis of maximum daily rainfalls was investigated for Golestan province located in the northeastern Iran. This study aimed to find appropriate regional frequency distributions for maximum daily rainfalls and predict the return values of extreme rainfall events (design rainfall depths) for the future. L-moment regionalization procedures coupled with an index rainfall method were applied to maximum rainfall records of 47 stations across the study area. Due to complex geographic and hydro-climatological characteristics of the region, an important research issue focused on breaking down the large area into homogeneous and coherent sub-regions. The study area was divided into five homogeneous regions, based on the cluster analysis of site characteristics and tests for the regional homogeneity. The goodness-of-fit results indicated that the best fitting distribution is different for individual homogeneous regions. The difference may be a result of the distinctive climatic and geographic conditions. The estimated regional quantiles and their accuracy measures produced by Monte Carlo simulations demonstrate that the estimation uncertainty as measured by the RMSE values and 90% error bounds is relatively low when return periods are less than 100 years. But, for higher return periods, rainfall estimates should be treated with caution. More station years, either from longer records or more stations in the regions, would be required for rainfall estimates above T=100 years. It was found from the analyses that, the index rainfall (at-site average maximum rainfall) can be estimated reasonably well as a function of mean annual precipitation in Golestan province. Index rainfalls combined with the regional growth curves, can be used to estimate design rainfalls at ungauged sites. Overall, it was found that cluster analysis together with the L-moments based regional frequency analysis technique could be applied successfully in deriving design rainfall estimates for northeastern Iran. The approach utilized in this study and the findings are of great scientific and practical merit, particularly for the purpose of planning for weather-related emergencies and design of hydraulic engineering structures.  相似文献   

中南地区矿山环境地质现状与恢复治理分区   总被引：1，自引：0，他引：1  

蔡锦辉  张帆  汪雄武  王晓地 《华南地质与矿产》2008,(2):49-57

通过对中南地区矿产开发情况的综合,阐明了该地区矿山开发中遇到的主要环境地质问题,并依据该地区矿山开发所引起的环境地质问题的严重程度,对地域进行了分级,提出了防治措施和对策建议。  相似文献   

The distribution of daily snow water equivalent in the central Italian Alps     

Daniele Bocchiola  Renzo Rosso 《Advances in water resources》2007

The statistical distribution of the daily Snow Water Equivalent (SWE) is investigated for a network of gauging stations in the Alpine part of Lombardia region, in the central Italian Alps. An event based data analysis is carried out using a 14 year long data set dating back to 1989. SWE is estimated when the new snow depth is greater than 6 cm. The SWE sample average in time is shown to be related to physiographic attributes of the gauging area, thus not being homogeneous in space. The values of SWE scaled by their average, or index value, instead show well approximated homogeneity of the second order moment, or coefficient of variation, in space. This suggests the use of a regional approach for frequency estimation of SWE. The frequency of occurrence of the normalized values of SWE is evaluated and tentatively accommodated by four probability distributions, often adopted in statistical modeling of hydrological variables. The Lognormal distribution shows the best performance. Single site distribution fitting is then carried out using the regional distribution, providing satisfactory results.  相似文献   

分层分区分景相结合的区域土地利用/覆盖分类方法——以浙江钱塘江流域分类为例   总被引：2，自引：0，他引：2  

张丽苏  吴嘉平 《国土资源遥感》2007,18(3):74-77

在土地利用/覆盖研究中，对于范围广、地域差别大的地区，仅用同一标准对遥感图像进行分类往往难以得到理想的效果。 本文以浙江省钱塘江流域为例，通过对Landsat TM数据各波段组合，首先提取水层和山层信息，然后采用掩模法提取平原丘陵层信 息，并根据地形地貌和土地利用现状的差异，将平原丘陵层划分为6个区，当所划分区域内各景的影像时相不一致时，再对该区进 行分景处理。最后，分别对每层、每区和每景图像进行训练样本的选择和监督分类。试验结果表明，结合分层、分区和分景的监督 分类方法是一种适合于较大区域土地利用/土地覆盖分类的有效方法。  相似文献   

Quantification and regionalization of groundwater–surface water interaction along an alluvial stream     

Jesper H. Langhoff  Keld R. Rasmussen  Steen Christensen   《Journal of Hydrology》2006,320(3-4):342-358

In the present study, groundwater seepage to an alluvial stream and two tributary streams was examined at nine field sites using hydrological, geophysical, and geomorphological observations. The data indicate that seepage enters the streams in the following ways: (i) directly through the streambed; (ii) as nearly superficial flow from diffuse discharge areas on the flood plains or; (iii) as a combination of (i) and (ii). At about 40% of the sites more than 50% of seepage flows through the streambed. Moreover, it was found that the ratio C, defined as the width of the wet zone of the flood plain divided by the effective width of the stream, can be used as an indicator of the percentage of water entering the stream directly through the streambed. When C is small streambed seepage is large, while when C is large streambed seepage is small and ground water enters the stream mainly as nearly superficial or over-bank flow from the wet zone.  相似文献   

区域开发与区域划分：中国古代的历史经验   总被引：5，自引：1，他引：5  

陈述彭  曾杉 《地理科学》1997,17(2):97-104

中国人很早以前就有区域发异的概念，由此产生的中持续发展思维成功地运用到三角洲的开发和三角洲文明的形成之中。在以海岸带为基线，面向内陆和面向海洋的区域开发与区域交往的漫长历程中，古代留下众多历史启示。古往今来，区域划分一直是中国区域开发的重要组成部分。５０００年文明成功的经验与失败的教训，锤炼出区域划分的目标：寻求区域内部的向心力和亲和力，保持中央集权与地方分权的最佳临界状态，分级处理模糊边界。  相似文献   

Efficient regionalization techniques for socio‐economic geographical units using minimum spanning trees     

R. M. AssunÇão  M. C. Neves  C. Da Costa Freitas 《International journal of geographical information science》2013,27(7):797-811

Regionalization is a classification procedure applied to spatial objects with an areal representation, which groups them into homogeneous contiguous regions. This paper presents an efficient method for regionalization. The first step creates a connectivity graph that captures the neighbourhood relationship between the spatial objects. The cost of each edge in the graph is inversely proportional to the similarity between the regions it joins. We summarize the neighbourhood structure by a minimum spanning tree (MST), which is a connected tree with no circuits. We partition the MST by successive removal of edges that link dissimilar regions. The result is the division of the spatial objects into connected regions that have maximum internal homogeneity. Since the MST partitioning problem is NP‐hard, we propose a heuristic to speed up the tree partitioning significantly. Our results show that our proposed method combines performance and quality, and it is a good alternative to other regionalization methods found in the literature.  相似文献