基于遥感与GIS的中国湖泊形态分析

基于2010年Landsat TM/ETM数据,结合Google Earth影像和其他资料,采用面向对象的分类方法,以30 m的分割尺度对图像进行分割,并通过比值指数、归一化差值水体指数及谱间关系等指数来提取水体信息,将水体分为河渠、湖泊及水库坑塘3类,并对分类结果进行精度验证,最终得到中国湖泊空间分布信息;以此为基础,计算出反映湖泊形态的景观指数(如形状指数、近圆形指数及分维数等),并结合湖泊的面积和湖泊岸线长度来说明湖泊的基本状况及其形状的复杂程度。结果表明:利用面向对象分类方法可以得到较高的分类精度,3种类型水体分类的总精度为93%,湖泊分类精度达到90%以上;在中国内陆,面积大于1.0 km2的自然湖泊2 477个,总面积约77 934.72 km2;在5个湖区中,青藏高原湖区的湖泊面积最大,占湖泊总面积的54.34%,其形状指数和分维数均值为最小,湖泊形态比较简单;东部平原湖区降雨充沛,水系发达,其形状指数和分维数均值最大,湖泊岸线更加曲折,形态复杂多变;通过分析得出,形状指数与分维数有明显的相关性(R2=0.95),湖泊岸线分维数值越高,其形状指数越大,岸线越复杂。     

数学形态学在遥感影像云层识别中的应用

针对传统遥感影像质量评价中云层覆盖量无法定量评价的问题,文章提出采用利用边缘信息的阈值分割结合数学形态学方法来提取遥感影像云层覆盖范围。利用边缘信息的阈值分割方法能够有效利用影像自身信息来改善分割结果,再结合形态学方法,进而能消除道路、房屋等大部分噪声信息,最终实现遥感影像上不同特征云层覆盖范围的自动提取。基于浙江全省高分辨率遥感影像的实验结果表明:该方法能够快速有效地识别出遥感影像上云层覆盖范围,研究结果对于遥感影像云层覆盖的自动评价具有参考价值。     

基于三维计盒法的城市空间形态分维计算和分析

将城市形态分形维数的二维盒维数方法扩展到三维空间,提出了一种三维盒维数计算方法;并且针对以往城市分形研究中人工判定无尺度区不精确的问题,借鉴了二阶导数的方法进行分形无尺度区的自动识别;以扬州市中心城区2003年与2012年两期数据为例,详细介绍了城市三维空间形态分维计盒法的计算过程。实验结果显示,通过二阶导数方法能够有效的自动识别无尺度区;2003年与2012年数据无尺度区线性拟合确定系数R2均在0.996以上,扬州市三维空间形态具有明确的分形特征;2012年较2003年三维分维值的增加表明扬州市城市三维空间利用总体上趋于有效与紧凑。     

A method for delineating a hierarchically networked structure of urban landscape

We developed a new approach combining statistical and graphical methods to build a hierarchically networked structure for understanding spatial characteristics of urban landscapes at multiple scales. Natural breaks optimization algorithm is applied to determine the optimal number of urban land hierarchies and assign discrete patches into ordered sub-groups according to a selected geometric or functional attribute. Patches contained in a sub-group are linked to the patches in the next sub-group according to the spatial relationships between the patch centroids and Voronoi cells. The conceptual foundations and technical details of this approach are elaborated in the case study of building a hierarchically networked structure of urban built-up patches in Beijing. This approach can be applied to quantify landscape patterns of other land uses to facilitate assessments of interconnection between various types of land uses at varied hierarchical levels (spatial scales) and to evaluate ecological service functions of urban built infrastructures.     

Heat-flow regimes and the hydrate stability zone of a transient,thermogenic, fault-controlled hydrate system (Woolsey Mound northern Gulf of Mexico)

This study aims to constrain the base of the hydrates stability field in structurally complexsites using the case of Woolsey Mound, a fault-controlled, transient, thermogenic hydrates system, in Mississippi Canyon Block 118, northern Gulf of Mexico. We have computed the base of the hydrates stability field integrating results from a recent heat-flow survey, designed to investigate geothermal anomalies along fault zones which exhibit different fluid flux regimes. An advanced “compositional” simulator was used to model hydrate formation and dissociation at Woolsey Mound and addresses the following hypotheses:

• 1.Migrating thermogenic fluids alter thermal conditions of the Hydrate Stability Zone (HSZ), so heat-flow reflects fault activity;
• 2.Gas hydrate formation and dissociation vary temporally at active faults, temporarily sealing conduits for migration of thermogenic fluids;
• 3.High salinity and inclusion of thermogenic gases with higher molecular weight than methane produce opposite effects on the depth to the bottom of the hydrate stability zone.

Applications of results include identifying and quantifying hydrate deposits in shallow sediments using an interdisciplinary approach that includes multiple resolution seismic data evaluation, geological and geochemical groundtruthing and heat-flow analyses as a proxy for activity along faults.     

2012年登陆我国热带气旋的气候特征分析

利用1981—2012年热带气旋数据资料,统计分析了2012年登陆我国热带气旋的特征;并且利用美国国家环境预报中心(NCEP)再分析数据和美国国家海洋大气管理局(NOAA)的avhrr卫星数据,分析了其原因。结果表明,2012年登陆热带气旋登陆地点偏北是由当年夏季西北太平洋副热带高压(以下简称"副高")的脊线位置偏北,热带季风槽位置偏北等因素所造成的。登陆热带气旋强度偏强和北太平洋(30°N、160°—170°E)区域海温表现出很好的正相关关系,与东太平洋(20°N、120°W)区域海温呈现了负相关关系。     

Gully-head morphology and implications for gully development on abandoned fields in a semi-arid environment,Sierra de Gata,southeast Spain

In this paper we examine whether gully-head morphology can be used as an indicator for gully development and, hence, for sediment production. A survey was conducted at five hillslopes in the Sierra de Gata where different types of channel heads occur close to each other. The survey included measurements of morphologic and pedologic properties, ground surface, channel and catchment characteristics of every gully head present (n = 59). On the basis of the observed morphologies, the heads were subdivided into four types: gradual, transitional (a short inclined section), abrupt and rilled-abrupt. The analyses showed that it is possible to explain the differences of gully heads and the role of some environmental factors on the basis of their morphologies, at least for the gradual and the abrupt types. The results suggested that steep headcuts (abrupt) were formed from secondary headcuts in the channel, which migrated upstream. The abrupt headcuts were always formed in more than one soil layer of which one was a resistant (stony) layer. However, shear strength measurements (at saturation) showed that the top layer was not always the most resistant one. Width–depth relationships indicated that gradual type headcuts were controlled by fluvial processes and abrupt headcuts by a combination of fluvial and mass-wasting processes. Gradual types occurred more downslope than the abrupt types suggesting that the incisions started by fluvial processes and migrated upwards when knickpoints developed in the channel. The rilled-abrupt types are still actively retreating. Thus, the abrupt types correspond to slower retreat rates. Abrupt gully heads may deteriorate into transitional types when plunge-pool erosion becomes less effective. The conceptual model is supported by data from ephemeral gullies in two other study areas (Sierra de la Torrecilla, Spain, and Alentejo, Portugal). Copyright © 1999 John Wiley & Sons, Ltd.     

Mountain ordering: A method for classifying mountains based on their morphometry

A new method for classifying mountain morphology, ‘mountain ordering,’ is proposed, and quantitative expressions for various morphological parameters of two ordered mountains in northern Japan were obtained using this method. Mountain order was defined in terms of the closed contour lines on a topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation; they are identified as m + 1th-order mountains, where m represents the order of the enclosed, lower-order mountains. The geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters. The relationships between mountain order and these morphological parameters follow a form similar to that of Horton's laws, and permit the calculation of the ratios of number, area and height; these parameters are sufficient to express the magnitude of a mountain's dissection. The size–frequency distribution for area and height shows self-similarity for ordered mountains, and determines their fractal dimensions. Furthermore, the relationship between area and height, which has the form of a power function, describes the relief structure of ordered mountains. Copyright © 1999 John Wiley & Sons, Ltd.     

一次弱对流引发局地特大暴雨天气的诊断分析

对2003年8月28-29日宁陕特大暴雨过程诊断分析结果表明：特大暴雨发生在低层辐合、高层辐合,不利于强对流发展的弱对流环境中。低层850～700hPa低涡倒槽为特大暴雨提供了辐合上升运动和充沛的水汽条件。850hPa几股来自不同方向、性质不同的气流相汇在宁陕上空,强水汽辐合是特大暴雨形成的主要原因。     

我国矿物晶体形貌学四十年的回顾与展望

矿物晶体形貌学在我校的创建和发展基本上是我国这一学科沿革的缩影。彭志忠教授1959～1965年开创了《晶体测量》的教学、科研和实验室建设,填补了我国矿物学中一个分支学科的空白。后来中断了。1982年以来得以恢复并引入微形貌学的内容,从而不仅建成了较完善的现代《矿物晶体形貌学》学科,亦促进了我国矿物学的全面发展。