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利用2007～2010年6～9月四川加密自动气象站雨量监测资料,分析了小时雨量特征,并结合其间的泥石流、滑坡地质灾害个例,对泥石流、滑坡发生时的降雨特点进行了分析。结果表明,1500m以下小时平均雨强较大时段出现在1～7时,1500m以上小时雨强较大时段出现在夜间10时至次日8时,短历时强降雨是诱发泥石流的关键因素,而滑坡的发生受降水的累计和滞后效应影响。海拔1500m以下,发生泥石流、滑坡一般需要50mm的降水,1500～3500m海拔,6小时降水有15～20mm,就有可能引发泥石流、滑坡,而在3500m以上,6小时降水有10～15mm即可。 相似文献
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基于2005~2007年汛期成都区域气象中心的中尺度区域集合预报产品和德国、日本数值预报模式的降水产品,针对四川暴雨构建样本资料,采用支持向量机方法(Support Vector Machines,简称SVM)建立暴雨预警模型,开展暴雨预警预报试验,并将建立的模型应用于2008年汛期四川省逐日暴雨有无预报。检验结果表明,基于区域中尺度集合预报产品建立的SVM暴雨预警模型,对暴雨定点预报有较强的指示作用,暴雨预警指数为0.2。 相似文献
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利用西南地区2004、2005年夏季的实况温度对G rapes模式输出的2m温度预报产品进行检验,结果表明,不管是单日预报误差还是月平均预报误差,都没有随预报时效的延长而增大,对四川盆地大部分地区,模式预报温度偏高,对重庆、云南、贵州及川西高原南部的温度预报,基本上表现为14时偏高,02时偏低,对川西高原北部和西藏则表现为预报温度偏低。分析表明,模式中对高原地形处理的不真实是温度预报产生误差的重要原因之一,利用回归分析方法能对模式温度预报进行有效的订正。检验分析结果为进一步改进模式,提高要素预报产品质量提供了一定的依据。 相似文献
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1988～1998年北半球积雪时空变化特征分析 总被引：17，自引：0，他引：17
利用NOAA提供的北半球近10年(1988～1998)逐周雪盖观测资料，通过引入年或季节累积雪盖周数作为对雪量累积情况的定量衡量，对北半球雪盖变化时空特征进行了分析。结果表明:近10年来，北半球积雪年际变化的关键区位于青藏高原、蒙古高原、欧洲阿尔卑斯山脉及北美中西部，其中青藏高原是北半球积雪异常变化最强烈的区域。青藏高原和欧亚大陆其他地区积雪变化的关联表现为两种不同的时空变化型，第一种型表现为青藏高原地区和其他地区(如欧洲、俄罗斯远东地区)积雪的同位相趋势性增多；第二种型表现为青藏高原地区和中亚地区积雪变化同位相，而和蒙古高原－我国东北地区积雪变化反位相的年际振荡。 相似文献
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本文在简要介绍山西省地下水动态观测历史及现状的基础上,分析了省内地下水流向、动态变化特性,归纳了山西省地下水动态的基本特点,最后提出了加强地下水动态观测工作的四点结论及建议. 相似文献
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从"四地"期刊载文审视中国农业与乡村地理学研究发展特征 总被引：1，自引：0，他引：1
基于中国学术期刊出版总库所提供的《地理学报》《地理科学》《地理研究》《地理科学进展》（简称“四地”期刊）创刊以来至2020年12月间的农业与乡村地理学论文数据,采用Citespace可视化科学文献计量方法,对566篇文献的主题、引文和关键词等特征进行可视化分析。系统梳理了农业与乡村地理学术论文所反映的主题脉络、知识演进、历史热点、研究机构发展和发文作者分析。这些分析充分体现出了中国农业与乡村地理学研究的发展历程、目前的主要研究议题与未来的发展趋势。研究结果显示,农业地理、聚落与古村落、土地利用及其发展模式、乡村居民点及其空间格局、城乡一体化、新农村建设、乡村重构、乡村振兴和城乡融合发展等主要研究议题是不同时期的研究聚焦点。从研究热度看大致经历了由以农业地理研究为主,转向农业地理与乡村聚落地理并驾齐驱,再到城乡融合与乡村振兴研究3个阶段。其研究发展过程呈现出3大转向：① 由单一的农业地理和乡村聚落地理转向综合的农业与乡村地理学研究;② 从单一的农业生产要素、社会经济要素格局研究转向区域城乡人地系统融合的过程、机制和影响研究;③ 由传统的调研统计、田野观测、数字模拟技术方法转向大数据、多源时空监测模拟和农业地理工程实践。乡村转型-城乡融合-乡村振兴-高质量发展将成为未来城乡发展的大逻辑、新常态,也是未来农业与乡村地理学研究的重点和方向。主要研究议题方面有乡村地域类型、乡村功能转型、乡村空间重构、乡村聚落重构、乡村人居环境质量、乡村发展的新因素及其作用机制、乡村弹性与可持续性发展、乡村产业结构调整与升级、城乡基础设施与服务统筹规划建设等。学科发展应注重综合研究,深化对农业与乡村发展新驱动力的认识,切实加强乡村地理学研究的理论与方法创新,借以更好地服务于国家乡村振兴战略。 相似文献
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Paleogeographic evolution of the Lower Yangtze region and the break of the “platform-slope-basin” pattern during the Late Ordovician 总被引：1，自引：0，他引：1
Wide distribution of the black shales and diversification of the graptolite fauna in South China during the Late Ordovician resulted from its unique paleogeographic pattern, which was significantly affected by the paleogeographic evolution of the Lower Yangtze region. In the study, 120 Upper Ordovician sections from the Lower Yangtze region were collected, and a unified biostratigraphic framework has been applied to these sections to establish a reliable stratigraphic subdivision and correlation. Under the unified time framework, we delineate the distribution area of each lithostratigraphic unit, outline the boundary between the sea and land, and reconstruct the paleogeographic pattern for each graptolite zone. The result indicates that, with the uplift and expansion of the ‘Jiangnan Oldland' in the beginning of the late Katian, the oldland extended into the Yangtze Sea gradually from south to north, which finally separate the Jiangnan Slope and the Yangtze Platform. Consequently,the longstanding paleogeographic pattern of "platform-slope-basin" in South China was broken. The paleogeographic change led to sedimentary differentiation among the two sides of the ‘Jiangnan Oldland' during the Late Ordovician. This event also led to the closure of the eastern exit of the Upper Yangtze Sea, and formed a semi-closed, limited and stagnant environment for the development of the organic-rich black shales during the Late Ordovician. The major controlling factors of these paleogeographic changes in the Lower Yangtze region were not consistent from the Katian to the Hirnantian. In the late Katian, the sedimentary differentiation between the east and west sides mostly resulted from regional tectonic movement-the Kwangsian Orogeny.However, during the Hirnantian, the whole Yangtze region became shallower, which was mostly influenced by the concentration of the Gondwana ice sheet and the consequent global sea level drop. 相似文献
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作为深时数字地球项目的底层框架,全球古地理重建模型包括地质历史时期板块的位置和运动轨迹以及地表特征两方面的内容。过去数十年里,基于不同方法、不同资料的全球古地理重建模型不断涌现。综合古地磁学、古生物学、沉积学、地球物理、地球化学以及地球动力学领域的知识与资料解释古地理,并建立起数字化、可修改、随时间演变的模型是当前常见的方法。文章介绍了国内外全球古地理重建模型的构建方法,并比较了六种主流的重建模型(PaleoMap、PLATES、UNIL、GOLONKA、GMAP和EarthByte),旨在为国内相关领域研究提供参考。文章还介绍了数字化全球重建古地理模型在古气候、板块构造驱动力以及盆地演化方面的应用及知识发现。通过对现存模型的介绍,提出展望,希望在深时数字地球计划的框架下整合国内外优秀科学家,重新设计并建立真正统一的四维古地理重建模型。 相似文献
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LUO Ya YANG Shengtian ZHAO Changsen LIU Xiaoyan LIU Changming WU Linna ZHAO Haigen ZHANG Yichi 《地理学报》2014,24(5):802-814
In areas with topographic heterogeneity, land use change is spatially variable and influenced by climate, soil properties, and topography. To better understand this variability in the high-sediment region of the Loess Plateau in which soil loss is most severe and sediment diameter is larger than in other regions of the plateau, this study builds some indicators to identify the characteristics of land use change and then analyze the spatial variability as it is affected by climate, soil property, and topography. We build two indicators, a land use change intensity index and a vegetation change index, to characterize the intensity of land use change, and the degree of vegetation restoration, respectively. Based on a subsection mean method, the two indicators are then used to assess the spatial variability of land use change affected by climatic, edaphic, and topographic elements. The results indicate that: 1) Land use changed significantly in the period 1998-2010. The total area experiencing land use change was 42,302 km2, accounting for 22.57% of the study area. High-coverage grassland, other woodland, and forest increased significantly, while low-coverage grassland and farmland decreased in 2010 compared with 1998. 2) Land use change occurred primarily west of the Yellow River, between 35 and 38 degrees north latitude. The four transformation types, including (a) low-coverage grassland to medium-coverage grassland, (b) medium-coverage grassland to high-coverage grassland, (c) farmland to other woodland, and (d) farmland to medium-coverage grassland, were the primary types of land use change, together constituting 60% of the area experiencing land use change. 3) The spatial variability of land use change was significantly affected by properties of dryness/wetness, soil conditions and slope gradient. In general, land use changed dramatically in semi-arid regions, remained relatively stable in arid regions, changed significantly in clay-rich soil, remained relatively stable in clay-poor soil, changed dramatically in steeper slopes, and remained relatively stable in tablelands and low-lying regions. The increase in vegetation coincided with increasing changes in land use for each physical element. These findings allow for an evaluation of the effect of the Grain to Green Program, and are applicable to the design of soil and water conservation projects on the Loess Plateau of China. 相似文献