青藏高原冬季积雪年代际变化及对中国夏季降水的影响   总被引：5，自引：1，他引：4       下载免费PDF全文

宋燕  张菁  李智方  赵平 《高原气象》2011,30(4):843-851

通过对1961-2006年青藏高原原始测站资料的筛选、剔除和插补等处理,得到了一套具有51站连续的、长序列的积雪观测资料。利用国家气候中心整理的1951-2006年中国160站月降水和月平均气温资料,分析了青藏高原冬、春季积雪年代际变化特征与中国夏季降水和气温的关系,并研究了全球变暖影响下青藏高原积雪对中国大陆对流层温...  相似文献   

International wood trade and forest change: A global analysis     

Thomas Kastner  Karl-Heinz ErbSanderine Nonhebel 《Global Environmental Change》2011,21(3):947-956

Throughout history, humans have transformed natural forests into agricultural land, settlement areas and managed forests. Studies on the dynamics of forest change are one of the mainstays in land change science. The forest transition theory offers a powerful tool to analyze changes in human interference with forests. At the national level, a range of factors have been found to influence a country's forest change. The role of international wood product trade has, however, rarely been studied based on empirical data. We offer a global assessment of how this trade helps shape observed forest change, by relating forest stock change to net trade of wood products for the period 1997-2007 and by localizing the origin of wood consumed in a given nation. For many nations, traded wood products have a relevant impact on the course of ongoing forest transitions. We develop a general typology of how wood product trade can influence forest change and place various nations within this framework. We find that many wealthy nations with returning forests seem to accelerate this return by importing wood products. These imports appear to be provided by two main types of wood exporters: (a) by wealthy countries with low population densities and stable forests and (b) by relatively poor countries with declining forests, employing increasing population and welfare levels. We discuss these findings in the light of general theories on land use transitions and forest change and conclude by highlighting implications for national forest policies and global environmental governance, aiming at reducing negative impacts of wood products and enhancing the positive role they can play in replacing more fossil fuel intensive products.  相似文献   

Living it up: Super-rich enclave and transnational elite urbanism in Singapore   总被引：2，自引：0，他引：2  

Choon-Piew Pow 《Geoforum》2011,42(3):382-393

Notwithstanding the burgeoning scholarship on enclave urbanism, urban gating has often been pigeonholed as an intra-urban development that is somewhat ‘epiphenomenal’ to wider global processes. Overlooked in the literature is how gated communities as globally-oriented spaces are intertwined with the transnational lifeworlds of its elite inhabitants. As key sites where transnational super-rich elites organize their consumption and reproduce their purportedly global lifestyle, gated communities are now emerging as a new ‘meta-geographical form’ that circulates in and around rapidly globalizing cities. Drawing on the case study of Sentosa Cove, an exclusive waterfront gated community in Singapore catering to ‘high net-worth’ residents, this paper critically examines how elite localities and transnationalism are being socially and spatially reproduced in the city-state. To this end, the paper makes a distinct contribution by bringing to bear critical transnationalism perspectives in the understanding of urban gating and the privileged geographies of the global super-rich.  相似文献   

Application of particle swarm optimization on self-potential data   总被引：1，自引：0，他引：1  

Ertan Pek?en  Türker Yas  A. Yekta Kayman  Co?kun Özkan 《Journal of Applied Geophysics》2011,75(2):305-318

Particle swarm optimization (PSO) is a global search method, which can be used for quantitative interpretation of self-potential data in geophysics. At the result of this process, parameters of a source model, e.g., the electrical dipole moment, the depth of the source, the distance from the origin, the polarization angle and regional coefficients are estimated. This study investigates the results and interpretation of a detailed numerical data of some simple body responses, contaminated and field data. The method is applied to three field examples from Turkey and the results are compared with the previous works. The statistics of particle swarm optimization and the corresponding model parameters are analyzed with respect to the number of generation. We also present the oscillations of the model parameters at the vicinity of the low misfit area. Further, we show how the model parameters and absolute frequencies are related to the total number of PSO iterations. Gaussian noise shifts the low misfit area region from the correct parameter values proportional to the level of errors, which directly affects the result of the PSO method. These effects also give some ambiguity of the model parameters. However, the statistical analyses help to decrease these ambiguities in order to find the correct values. Thus, the findings suggest that PSO can be used for quantitative interpretation of self-potential data.  相似文献   

Changes in dissolved silica mobilization into river systems draining North America until the period 2081–2100     

Nils Moosdorf  Jens Hartmann  Ronny Lauerwald 《Journal of Geochemical Exploration》2011

Dissolved silica (DSi) is an important control on algae abundance and species composition both in freshwater and marine ecosystems. Although continental and global budgets for DSi exist, understanding of the spatial variability of DSi cycles needs to be improved on those scales. In this study, an empirical model of DSi mobilization into river systems is extrapolated on a 1.4 km² grid to North America. To analyze changes in DSi mobilization patterns, DSi mobilization is estimated regionally for present day runoff and a runoff projection ensemble for the period 2081–2100. The model predicts present day annual DSi fluxes for the monitored area within 6% of the calculated fluxes. Possible biases by processes not directly represented by applied geodata are discussed (e.g. land use and ecosystem influences) and found to be only minor on the regional scale. Uncertainty of the results is discussed based on a literature review. The projected DSi-mobilization rates at high latitudes for the present day conditions may be overestimated. However, the projected change rate for the period 2081–2100 might even be underestimated, due to e.g. increased thawing in certain permafrost regions, which was not included in the model.  相似文献   

Limit equilibrium method based on an approximate lower bound method with a variable factor of safety that can consider residual strength     

Y.M. Cheng  D.Z. Li  L. Li  Y.J. Sun  R. Baker  Y. Yang 《Computers and Geotechnics》2011

In this paper, the factor of safety for a prescribed slip surface will be determined from an equivalent lower bound method (extremum principle), which can satisfy all equilibrium conditions without an interslice force function. This approach will give an overall factor of safety close to that from the classical methods for normal problems, while the thrust line, the local factor of safety for individual slice/block and the progressive yielding phenomenon can be estimated, which will be useful for some special cases. The force and moment equilibrium of every slice will be satisfied, while the location of the thrust line will always be acceptable in the present formulation. To solve the difficult optimisation problem, an innovative coupled particle swarm/harmony search algorithm is proposed in this paper, and a practical engineering problem for which the factor of safety is close to 1.0 is used to illustrate the consideration of the residual strength in the limit equilibrium slope stability analysis.  相似文献   

国土资源移动执法监察管理信息系统设计与实现     

陈欣  欧孝奇  田燕 《国土资源信息化》2011,(5):42-45

在国土资源执法监察信息化建设的背景下,通过对市、县级国土资源执法监察业务的分析与梳理,构建了动态巡查和卫片执法监察的业务模型和业务流程,完成了移动执法监察管理信息系统的设计与开发。本文对系统的总体架构、系统功能、系统特点和应用情况作了简要介绍。  相似文献   

Impact of Spin-up Forcing on Vegetation States Simulated by a Dynamic Global Vegetation Model Coupled with a Land Surface Model     

LI Fang  ZENG Xiaodong  SONG Xiang  TIAN Dongxiao  SHAO Pu  ZHANG Dongling 《大气科学进展》2011,28(4):775-788

A dynamic global vegetation model (DGVM) coupled with a land surface model (LSM) is generally initialized using a spin-up process to derive a physically-consistent initial condition. Spin-up forcing, which is the atmospheric forcing used to drive the coupled model to equilibrium solutions in the spin-up process, varies across earlier studies. In the present study, the impact of the spin-up forcing in the initialization stage on the fractional coverages (FCs) of plant functional type (PFT) in the subsequent simulation stage are assessed in seven classic climate regions by a modified Community Land Model’s Dynamic Global Vegetation Model (CLM-DGVM). Results show that the impact of spin-up forcing is considerable in all regions except the tropical rainforest climate region (TR) and the wet temperate climate region (WM). In the tropical monsoon climate region (TM), the TR and TM transition region (TR-TM), the dry temperate climate region (DM), the highland climate region (H), and the boreal forest climate region (BF), where FCs are affected by climate non-negligibly, the discrepancies in initial FCs, which represent long-term cumulative response of vegetation to different climate anomalies, are large. Moreover, the large discrepancies in initial FCs usually decay slowly because there are trees or shrubs in the five regions. The intrinsic growth timescales of FCs for tree PFTs and shrub PFTs are long, and the variation of FCs of tree PFTs or shrub PFTs can affect that of grass PFTs.  相似文献   

Conflicts over industrial tree plantations in the South: Who, how and why?     

Julien-Franois Gerber 《Global Environmental Change》2011,21(1):165-176

Industrial tree plantations for wood, palm oil and rubber production are among the fastest growing monocultures and are currently being promoted as carbon sinks and energy producers. Such plantations are causing a large number of conflicts between companies and local populations, mostly in the tropics and subtropics. Within a political ecology framework, the present paper investigates the nature of such conflicts as related to the alleged impacts of the plantations, the protesters involved, and the modalities of the conflicts with a special emphasis on their outcomes. Relying on the most comprehensive literature review to date, corresponding to 58 conflict cases, I find that the prominent cause of resistance is related to corporate control over land resulting in displacements and the end of local uses of ecosystems as they are replaced by monocultures. Resistance includes the “weapons of the weak” and ranges from dialogue to direct confrontation and from local to international. It often involves NGOs, especially for legal issues. Demonstrations, lawsuits, road blockades and tree uprooting have been reported in several countries. Authorities have responded by repression in about half of the cases analysed, while popular struggles have been able to stop plantations in about one fifth, mainly through winning lawsuits or massive social unrest. While these movements can be regarded as classical land conflicts, they usually also have an ecological content, corresponding to forms of the “environmentalism of the poor”. The documented large number of such conflicts suggests that policies promoting large-scale tree plantations should be reappraised.  相似文献   

香港国家地质公园粮船湾组火山岩岩石学研究   总被引：2，自引：0，他引：2       下载免费PDF全文

邢光福吴振扬陶奎元伍世良  陈荣 姜杨 李龙明  余明刚 《中国地质》2011,38(4):1079-1093

在香港国家地质公园西贡火山岩园区,核心地质景观是白垩纪粮船湾组(Kkh)火山岩优美的六方形石柱(柱状节理),它们的岩石类型长期存在熔岩和火山碎屑岩之争。笔者等经野外调查和薄片岩石学研究,确认粮船湾组火山岩实属一种特殊的熔岩——流纹质碎斑熔岩,以普遍的柱状节理、斑晶具有碎斑结构和珠边结构、基质发育霏细结构和流动构造为特征;它们不仅代表了香港地区中生代最晚期火山喷发的产物,而且构成了西贡破火山机构的中央侵出相岩穹。推断粮船湾组火山岩石柱是地球上已知面积最大的流纹质碎斑熔岩石柱群(～150 km2),目前所见的火山岩石柱仅是长期剥蚀后的残余部分。  相似文献