Editorial     

《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2013,7(1):1-2

The assessment of rock-fall hazards is subject to significant uncertainty, which is not fully considered in general practice and research. This paper reviews and classifies the various sources of the uncertainty. Taking a generic framework for risk assessment as source, a probabilistic model is presented that consistently combines the different types of uncertainties, in order to obtain a unified estimate of rock-fall risk. An important aspect of the model is that it allows for incorporating all available information, including physical and empirical models, observations and expert knowledge, by means of Bayesian updating. Detailed formulations are developed for various types of information. Finally, two examples considering rock-fall risk on roads, with and without protection structures, illustrate the application of the probabilistic modeling framework to practical problems.  相似文献   

生态脆弱能源区人居环境与经济协调发展时空格局及演化机制——以晋陕蒙接壤区为例     

宋永永  薛东前  代兰海 《干旱区地理》2017,40(6):1328-1337

以晋陕蒙接壤区为例,运用综合指数法、协调发展度模型和PCA模型方法,构建协调发展变化模型,借助GIS和SPSS技术,研究2000-2015年生态脆弱能源区人居环境与经济协调发展时空特征,揭示人居环境与经济系统时空协调演进机制。结果表明：2000年以来,晋陕蒙接壤区人居环境与经济系统协调发展度长期处于勉强协调发展类型;县域人居环境与经济系统协调发展度由“北高南低”演化为“中部高周边低”的空间分异特征;榆阳区、府谷县、横山县、神木县、东胜区、准格尔旗、伊金霍洛旗的人居环境与经济系统协调发展度显著提升,河曲县、保德县、偏关县、兴县、达拉特旗和托克托县的协调发展度出现下降态势;人居环境与经济系统时空协调演进是居住环境因子、产业结构因子、基础设施因子、公共服务设施因子和政府宏观政策调控因子等多重动力因子综合驱动的结果。据此提出推进区域人居环境与经济系统向优质协调发展类型演进的对策建议。  相似文献   

近30多年江淮流域极端气温指数的时空变化分析:站点观测和再分析的对比     

吴晶璐  朱红芳  宗培书  惠品宏  汤剑平 《气象科学》2018,38(4):464-476

利用1979—2011年江淮流域的区域站点、NCEP/DOE和ERA-Interim再分析资料中的逐日最高、最低气温资料集,对比分析了近33 a江淮流域极端气温指数的时空变化特征,对再分析资料的再现能力进行检验和评估。结果表明:(1)近33 a来大部分极端气温指数及其趋势系数的空间分布都表现出南北向梯度分布特征,而极端最高、最低气温的极值区分布在长江三角洲地区;(2)夏日指数、作物生产指数、极端最高、极端最低、暖期长度指数和高百分位指数在年际变化中均有上升趋势,而且多次出现异常低值和异常高值;近10多年来,极端气温频率指数和百分位指数的年际变化趋势有所减缓;(3)月最高气温在近30 a中不断被突破,最低气温不断上升,而且高温天气日数也在不断增加,但低温日数逐渐减少;(4)再分析资料能较合理地再现大部分极端指数的时空变化和线性趋势特征,ERA-Interim比NCEP/DOE具有更好的再现能力。  相似文献   

Large-scale patterns in the distribution of planktonic and micronektonic biomass in the north-east Atlantic     

Ange  M. V.; Hargreaves  P. M. 《ICES Journal of Marine Science》1992,49(4):403-411

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An analysis of uncertainty in non-equilibrium and equilibrium geothermobarometry     

J. R. ASHWORTH  V. S. SHEPLEV  V. V. KHLESTOV  V. A. ANANYEV 《Journal of Metamorphic Geology》2004,22(9):811-824

In statistically optimised P–T estimation, the contributions to overall uncertainty from different sources are represented by ellipses. One source, for a diffusion‐controlled reaction at non‐equilibrium, is diffusion modelling of the reaction texture. This modelling is used to estimate ratios, Q, between free‐energy differences, ΔG, of reactions among mineral end‐members, to replace the equilibrium condition ΔG = 0. The associated uncertainty is compared with those already inherent in the equilibrium case (from end‐member data, activity models and mineral compositions). A compact matrix formulation is introduced for activity coefficients, and their partial derivatives governing error propagation. The non‐equilibrium example studied is a corona reaction with the assemblage Grt–Opx–Cpx–Pl–Qtz. Two garnet compositions are used, from opposite sides of the corona. In one of them, affected by post‐reaction Fe, Mg exchange with pyroxene, the problem of reconstructing the original composition is overcome by direct use of ratios between chemical‐potential differences, given by the diffusion modelling. The number of geothermobarometers in the optimisation is limited by near‐degeneracies. Their weightings are affected by strong correlations among Q ratios. Uncertainty from diffusion modelling is not large in comparison with other sources. Overall precision is limited mainly by uncertainties in activity models. Hypothetical equilibrium P–T are also estimated for both garnet compositions. By this approach, departure from equilibrium can be measured, with statistical uncertainties. For the example, the result for difference from equilibrium pressure is 1.2 ± 0.7 kbar.  相似文献   

On the information content of forest transpiration measurements for identifying canopy conductance model parameters     

S. C. Dekker  W. Bouten  F. C. Bosveld 《水文研究》2001,15(14):2821-2832

Generally, forest transpiration models contain model parameters that cannot be measured independently and therefore are tuned to fit the model results to measurements. Only unique parameter estimates with high accuracy can be used for extrapolation in time or space. However, parameter identification problems may occur as a result of the properties of the data set. Time‐series of environmental conditions, which control the forest transpiration, may contain periods with redundant or coupled information, so called collinearity, and other combinations of conditions may be measured only with difficulty or incompletely. The aim of this study is to select environmental conditions that yield a unique parameter set of a canopy conductance model. The parameter identification method based on localization of information (PIMLI) was used to calculate the information content of every individual artificial transpiration measurement. It is concluded that every measurement has its own information with respect to a parameter. Independent criteria were assessed to localize the environmental conditions, which contain measurements with most information. These measurements were used in separate subdata sets to identify the parameters. The selected measurements do not overlap and the accuracies of the parameter estimates are maximized. Measurements that were not selected do not contain additional information that can be used to further maximize the parameter accuracy. Thereupon, the independent criteria were used to select eddy correlation measurements and parameters were identified with only the selected measurements. It is concluded that, for this forest and data set, PIMLI identifies a unique parameter set with high accuracy, whereas conventional calibrations on subdata sets give non‐unique parameter estimates. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Seasonal Sensitivity on COBEL-ISBA Local Forecast System for Fog and Low Clouds     

Stevie Roquelaure  Thierry Bergot 《Pure and Applied Geophysics》2007,164(6-7):1283-1301

Skillful low visibility forecasts are essential for air-traffic managers to effectively regulate traffic and to optimize air-traffic control at international airports. For this purpose, the COBEL-ISBA local numerical forecast system has been implemented at Paris CDG international airport. This local approach is robust owing to the assimilation of detailed local observations. However, even with dedicated observations and initialization, uncertainties remain in both initial conditions and mesoscale forcings. The goal of the research presented here is to address the sensitivity of COBEL-ISBA forecast to initial conditions and mesoscale forcings during the winter season 2002–2003. The main sources of uncertainty of COBEL-ISBA input parameters have been estimated and the evaluation of parameter uncertainty on the forecasts has been studied. A budget strategy is applied during the winter season to quantify COBEL-ISBA sensitivity. This study is the first step toward building a local ensemble prediction system based on COBEL-ISBA. The conclusions of this work point out the potential for COBEL-ISBA ensemble forecasting and quantify sources of uncertainty that lead to dispersion.  相似文献   

城市热岛时空特征及其影响因素   总被引：3，自引：11，他引：3       下载免费PDF全文

肖荣波  欧阳志云  李伟峰  张兆明  王效科 《气象科学》2007,27(2):230-236

城市热岛强度呈周期性和非周期性交叉性时间变化,水平分布呈现单中心式、多中心、条状、辐射状、格网状等多种格局形式,同时具有明显的立体空间分布特征。城市热岛的形成原因及影响因素诸多,主要归纳为人为热量释放、下垫面性质和结构、植被减少、大气污染、城市格局、天气状况等。  相似文献   

气候变化国家评估报告(Ⅱ):气候变化的影响与适应   总被引：10，自引：1，他引：10  

林而达  许吟隆  吴绍洪  Ju Hui  Ma Shiming 《气候变化研究进展》2007,3(Z1):6-11

Significant and various impacts of climate change have been observed in China, showing both positive and adverse effects, dominantly the latter, in different sectors and regions. It is very likely that future climate change would cause significant adverse impacts on the ecosystems, agriculture, water resources, and coastal zones in China. Adoption of adaptive measures to climate change can alleviate the adverse impact, therefore such measures should be incorporated into the medium-and long-term national economic and social development plans. Because China has done relatively limited research on impact assessment and our understanding of climate change is incomplete, the current impact assessment methodologies used and results obtained contain many uncertainties. To reduce the uncertainties and develop effective and practical climate change adaptive measures in China, it is necessary to emphasize regional case studies on adaptive measures, enlarge the scope of climate change research, and strengthen the assessment of the impacts resulted from extreme weather/climate events.  相似文献   

数值预报发展的新方向——集合数值预报   总被引：5，自引：1，他引：5  

王太微  陈德辉 《气象研究与应用》2007,28(1):6-12

数值预报走过了百年的历史(V.Bjerknes,1904)[1],取得了了不起的成就,预报准确率有了很大的提高。但是,考虑到大气的非线性作用以及初值和模式造成的数值预报不确定性,要提高传统的单一确定性预报的技巧越来越难。基于大气初值的敏感性试验,Lorenz提出了数值预报发展的新方向——集合数值预报。通过介绍集合数值预报的基本思想和方法;并针对初值和模式的不确定性,概述现有集合数值预报成员的产生方法及国内外的研究进展;同时解释怎样检验集合预报的结果的论述,如何从众多的集合预报产品中提炼有用的信息及预报产品的释用。  相似文献