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81.
Dirk Böhme 《Limnologica》2011,41(2):80-89
Induced by a brine discharge study for a submerse gas storage cavern project, a suitable methodology for rapid impact assessment had to be found. In this paper a simple stochastic, stationary model is described for assessment of intensity and temporal variability of chloride pollution at the regional scale of the rivershed. Chloride concentration is used as a proxy of salinity. It is assumed to be the result of deterministic process (flow-dependent) and stochastic variation (estimated for boundary conditions and tributaries by an additive error term based on PERT distribution). This approach is suited to conduct Monte Carlo simulations in order to calculate long-time means and percentiles of the prospective in-stream chloride concentration (exposure model). The biocoenoses exposed to this pollution has to be evaluated in terms of chloride tolerance. Herefore Maximum Field Distributions (MFD) of relevant species (aquatic macrophytes, macroinvertebrates, fish) were compiled and merged to Species Sensitivity Distributions (SSDs). Critical aspects of MFD data quality are discussed. Chloride model simulations representing different discharge scenarios provide exposure parameters (e.g. 90th percentile) that can be compared with SSD-derived protection levels (e.g. maximum loss of 10% of taxa) to quantify and evaluate possible adverse effects as well as potential recolonisation in case of load removal. Crosslinks to conservation issues are relevant in the selection and position of rare or protected species in the SSD. As an analysis of the German legal framework and technical guidelines revealed lack of guidance and best practices for such assessment and impact evaluation, recent experience highlights serious needs in applied research. 相似文献
82.
SPT-N-based methods have been adopted for liquefaction assessment of soils during earthquakes for decades. However, there has not been a consistent way of assessing the accuracy and applicability of these methods. The Chi-chi earthquake of 1999, which has been the most serious ground shaking in Taiwan within the century, caused extensive liquefactions in mid-west alluvial deposits of the island. This paper assesses the prediction accuracy of several SPT-N-based methods using liquefaction and non-liquefaction incidents observed during the earthquake. A sensitivity study on commonly adopted parameters shows that the SPT blow count and peak ground acceleration are most sensitive in computing liquefaction potential. By comparing the error in predicting liquefaction and non-liquefaction incidents, this study concludes that Tokimatsu and Yoshimi’s method is more accurate than the other methods. However, the differences between prediction errors of various methods are minimal, indicating all of the methods examined are applicable for the 1999 earthquake in Taiwan. 相似文献
83.
84.
Eugen Rusu 《Ocean Engineering》2011,38(16):1763-1781
An evaluation of two state of the art phase averaged wave models for the transformation scale, SWAN and STWAVE, is carried out in the present work. The target area is the Obidos Bay located in the central part of the Portuguese continental nearshore. The wave input for the two models is provided by an offshore buoy. In order to compare the nearshore outputs of the wave models against in-situ measurements, a directional buoy and an ADCP, operating in intermediate water depth, are used. The wave parameters considered for comparisons are significant wave height, peak period and wave direction. Sensitivity analyses studies and evaluations in the spectral and geographical spaces concerning the results of the two models are also carried out in both intermediate and shallow water. The present study provides some information on the performances of the two wave models in different forcing conditions as well as on their sensitivity in relationship with various input parameters and some physical processes. STWAVE appears to be faster and more robust than SWAN, which on the other hand has more options and flexibility. In statistical terms the results are comparable. 相似文献
85.
横断山区近代气候变化的研究 总被引:6,自引:1,他引:5
横断山地处我国西南的藏东、川西和滇西北一带,境内地形复杂,平均海拔在3000米以上。长期以来,由于资料短缺,对该地区历史时期气候变化研究甚少。经实地考察,作者获取若干树木年轮标本,辅以其它类型资料,对该地区最近数百年来的温度、降水变化及气候类型演替,予以初步分析。并论及气候变化的振幅与周期性。 相似文献
86.
87.
Using field data from Agnico-Eagle’s Meliadine gold project located in Nunavut Territory in northern Canada, a coupled DFN–DEM approach was used to evaluate the rock mass mechanical properties at REV. Variability in the structural data gathered on site and the variability associated with the stochastic modeling process have an impact on discrete fracture model (DFN) properties. Through a sensitivity analysis, this paper assesses the influence of a variation in the DFN model input parameters’ values on the rock mass peak properties – uniaxial compressive strength, Young modulus and Poisson ratio. The results not only highlight the possibilities associated with DFN–DEM modeling in characterizing rock mass properties at the engineering scale, they also provide a systematic way to assess the critical structural parameters controlling the rock mass properties. 相似文献
88.
CoLM 模拟土壤温度和湿度最敏感参数的研究 总被引:2,自引:2,他引:0
合理的参数估计是提高陆面模式模拟能力的关键,而其过高的维数极大地增加了合理估计的难度。参数的敏感性分析,旨在针对目标变量找出最敏感的参数,从而实现在有限计算机资源条件下,对参数进行合理估计。本文以Common Land Model(CoLM)为研究对象,利用Morris 方法定性地从40 个参数中筛选出影响土壤温度和土壤湿度的敏感参数,并通过Sobol' 方法从敏感性顺序和各敏感参数的累积贡献率两个方面,对Morris 方法分析结果进行验证。在此基础上,本研究还利用Sobol' 方法对已筛选的参数做定量敏感性分析,最终确定参数的主效应、交互效应和总效应。研究结果表明,Morris 方法可以基于少量样本实现复杂的陆面模式的参数筛选,而Sobol' 方法的结果又从定量的角度描述了每个敏感参数对模型响应的影响程度,并且两种方法结论一致。 相似文献
89.
高纬度强对流与对流层上层水汽变化关系的数值模拟研究 总被引:2,自引:2,他引:0
应用WRF中尺度模式模拟了发生在黑龙江省西南部的一次区域性暴雨过程,通过云微物理参数化方案的敏感性试验,分析了对流云体中水汽垂直输送特征.结果表明:强对流活动使对流层上层局地水汽平均增加10倍以上,对流活动对于水汽的垂直输送以及对高层水汽含量的改变具有非常显著的作用.云微物理参数化方案,对于整个对流层水汽通量密度变化趋势有较好的表现.在不同方案中,0.5 ~9 km水汽通量密度及24 h总水汽垂直输送量,随高度变化差异较大.这是由平均垂直速度对不同方案敏感性造成的,不同的参数化方案,水汽通量最大值间最多相差可达27.9%.在不同的方案中,对流层上层加湿作用持续时间和对流层上层平均水汽混合比的最大值较敏感:对流活动可造成模拟区域对流层上层增湿持续16 ~20 h不等;对流层上层平均水汽混合比的最大值差异明显,最大可达15.8%.进行24 h平均后,上述物理量对方案的敏感性可减小到8.3%.所以,云微物理方案的不确定性对于暴雨过程的时间尺度是不可忽视的. 相似文献
90.
This work demonstrates how available knowledge can be used to build more transparent and refutable computer models of groundwater systems. The Death Valley regional groundwater flow system, which surrounds a proposed site for a high level nuclear waste repository of the United States of America, and the Nevada National Security Site (NNSS), where nuclear weapons were tested, is used to explore model adequacy, identify parameters important to (and informed by) observations, and identify existing old and potential new observations important to predictions. Model development is pursued using a set of fundamental questions addressed with carefully designed metrics. Critical methods include using a hydrogeologic model, managing model nonlinearity by designing models that are robust while maintaining realism, using error-based weighting to combine disparate types of data, and identifying important and unimportant parameters and observations and optimizing parameter values with computationally frugal schemes. The frugal schemes employed in this study require relatively few (10–1000 s), parallelizable model runs. This is beneficial because models able to approximate the complex site geology defensibly tend to have high computational cost. The issue of model defensibility is particularly important given the contentious political issues involved. 相似文献