等高线自动综合研究热点及趋势可视化分析

该文基于文献计量方法,从刊文量、文献共被引及高突现关键词等方面对该领域研究热点及趋势进行可视化分析.结果表明:①基于地形地貌结构化特征的等高线综合是永恒的研究主题;②数学方法始终为等高线综合研究提供有效的研究方法与手段;③已有算法的改进、算法效率及综合结果精度的提高将成为未来研究主要趋势之一;④GeoAI、大数据技术为未来等高线综合的研究提供了新契机、新的思路及发展方向.     

河系几何相似性的层次度量方法

已有的线群目标几何相似性度量方法主要基于数理统计的思想,通过统计整体变化信息计算几何相似性,缺少对局域特征的表达,并不适用于具有高度分形特征的河系。为此,本文将河系几何特征划分为3层次的信息特征：单条河流的形状特征、局部区域的结构特征、全局范围的分布特征。首先,结合角链码法与Hausdorff距离计算单条河流的形状相似度;然后,根据 “二八定律”确定局部特征区域,通过坐标系转换计算M： N的河系局域结构相似度;最后综合整体描述子得到全局分布相似度,并在该基础上,构建差异指标进行河系多尺度相似性计算与综合质量评价。实验表明,该方法的计算结果优于均值指标法,能有效应用于制图综合的质量评价。     

Exploring spatiotemporal patterns and physical controls of soil moisture at various spatial scales

Soil moisture variability of various spatial scales is analyzed based on empirical orthogonal function (EOF) method using soil moisture datasets with various spatial resolutions: 1 km eco-hydrological model simulation, 0.25° passive microwave (Advanced Microwave Scanning Radiometer for the Earth Observing System, AMSR-E) dataset, and 0.5° land surface model simulation from Climate Predictor Center (CPC). All three datasets generate EOFs that explain similar variances with those generated from in situ observations from agro-meteorological network. Using AMSR-E product and eco-hydrological model simulation, it is found that the primary spatial pattern of soil moisture obtained from watershed scale has a strong connection to topographic attributes, followed by soil texture and rainfall variability, as suggested by the correlation between the primary EOF mode (EOF1) of soil moisture and landscape attributes. However, the EOF analysis of both AMSR-E and CPC datasets at regional scale reaches the conclusion that soil texture indices, such as sand and clay content, is of higher importance to soil moisture EOF1 spatial pattern (explaining 61 % variance) than topography is. Furthermore, correlation between soil moisture EOF1 and soil property is higher in spring than in autumn, which indicates that soil water-holding and drainage capabilities are more important under dry conditions. At national scale, the combined effects of topographic feature and soil property are clearly exhibited in EOF1. The study results reveal that different emphases should be placed on accurate acquisition of landscape attributes for soil moisture estimation according to various spatial scales.     

Impacts of climate change on crop evapotranspiration with ensemble GCM projections in the North China Plain

As one of the key grain-producing regions in China, the agricultural system in the North China Plain (NCP) is vulnerable to climate change due to its limited water resources and strong dependence on irrigation for crop production. Exploring the impacts of climate change on crop evapotranspiration (ET) is of importance for water management and agricultural sustainability. The VIP (Vegetation Interface Processes) process-based ecosystem model and WRF (Weather Research and Forecasting) modeling system are applied to quantify ET responses of a wheat-maize cropping system to climate change. The ensemble projections of six General Circulation Models (GCMs) under the B2 and A2 scenarios in the 2050s over the NCP are used to account for the uncertainty of the projections. The thermal time requirements (TTR) of crops are assumed to remain constant under air warming conditions. It is found that in this case the length of the crop growth period will be shortened, which will result in the reduction of crop water consumption and possible crop productivity loss. Spatially, the changes of ET during the growth periods (ET_g) for wheat range from ?7 to 0 % with the average being ?1.5?±?1.2 % under the B2 scenario, and from ?8 to 2 % with the average being ?2.7?±?1.3 % under the A2 scenario/consistently, changes of ET_g for maize are from ?10 to 8 %, with the average being ?0.4?±?4.9 %, under the B2 scenario and from ?8 to 8 %, with the average being ?1.2?±?4.1 %, under the A2 scenario. Numerical analysis is also done on the condition that the length of the crop growth periods remains stable under the warming condition via breeding new crop varieties. In this case, TTR will be higher and the crop water requirements will increase, with the enhancement of the productivity. It is suggested that the options for adaptation to climate change include no action and accepting crop loss associated with the reduction in ET_g, or breeding new cultivars that would maintain or increase crop productivity and result in an increase in ET_g. In the latter case, attention should be paid to developing improved water conservation techniques to help compensate for the increased ET_g.     

中心城区广场公园绿地可达性研究

城市广场公园绿地的可达性是间接反映其布局是否合理的重要指标。本文运用多中心性模型测度了武汉市中心城区公共交通网络中心性,研究了武汉市中心城区公共交通网络和广场公园绿地空间分布规律以及空间结构;并利用邻近度和中间性两个指标,进一步分析了武汉市中心城区广场公园绿地的空间可达性。结果表明武汉市中心城区广场公园绿地具有以下特点:1)整体分布呈现较强的集聚性,同时区域差异明显;2)邻近度与"距离"呈线性负相关,从中心城区的中心到边缘,广场公园绿地中间性整体呈逐渐下降的趋势;3)位于中心城区中心的广场公园绿地空间可达性最佳,其覆盖区域交通网络中心性较高,可达时间相对较短,位于人口分布中心周围的广场公园绿地可达性较好,且可达性由城区中心向城区边缘逐渐递减。     

Analyzing regional economic impact and resilience: a case study on electricity outages caused by the 2008 snowstorms in southern China

When we think about the loss caused by natural disasters, we generally think about the direct economic loss. Although the direct economic loss is often obvious, the subsequent indirect economic loss can also be quite substantial. This research is a case study about the indirect economic impact of the Hunan electricity disruptions resulting from the 2008 snowstorms in southern China. Utilizing the computable general equilibrium model, this study shows that the indirect economic loss in Hunan Province resulting from electricity supply disruptions is estimated at USD 372 million over a 3-month recovery period. We also compare our results with other studies that use input–output models and discuss how the total regional economic resilience can mitigate economic losses through market substitutions and price changes.     

广东干湿气候的特征

提出一种月、季干湿气候指数，并用于广东各地干湿气候的分析，结果表明，广东以４－９月为湿季，１０月到翌年１月为干季，２－３月为干转湿的过渡期，干季短而湿季长，干湿季节的互换呈纬向自北向南推南，３－４月呈北湿南干，９月呈北干南湿，干湿季的转换时间与自然季节的转换基本相符。     

面状群(组)目标空间方向关系的形式化描述与计算

通过对各种空间方向关系形式化描述模型进行分析阐述,针对面状群(组)目标间方向关系的特点,本文提出了利用方向Voronoi图模型来计算面状群(组)目标之间的空间方向关系.该模型通过计算获得各个主方向上Voronoi边的长度值与方向Voronoi边法线总长度值的百分比,得到群(组)目标之间方向关系的定量表达;借助矩阵形式化描述获得源目标群相对于参考目标群方向关系的定性描述.实验表明,该模型方案具有可行性,能够对面状群(组)目标间的方向关系进行精确的描述.