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161.
Carly Hansen Javad Shafiei Shiva Spencer McDonald April Nabors 《Journal of the American Water Resources Association》2019,55(4):964-975
Streamflow monitoring in the Colorado River Basin (CRB) is essential to ensure diverse needs are met, especially during periods of drought or low flow. Existing stream gage networks, however, provide a limited record of past and current streamflow. Modeled streamflow products with more complete spatial and temporal coverage (including the National Water Model [NWM]), have primarily focused on flooding, rather than sustained drought or low flow conditions. Objectives of this study are to (1) evaluate historical performance of the NWM streamflow estimates (particularly with respect to droughts and seasonal low flows) and (2) identify characteristics relevant to model inputs and suitability for future applications. Comparisons of retrospective flows from the NWM to observed flows from the United States Geological Survey stream gage network over 22 years in the CRB reveal a tendency for underestimating low flow frequency, locations with low flows, and the number of years with low flows. We found model performance to be more accurate for the Upper CRB and at sites with higher precipitation, snow percent, baseflow index, and elevations. Underestimation of low flows and variable model performance has important implications for future applications: inaccurate evaluations of historical low flows and droughts, and less reliable performance outside of specific watershed/stream conditions. This highlights characteristics on which to focus future model development efforts. 相似文献
162.
中国资源型城市房价时空变化与影响因素分析 总被引:1,自引:0,他引:1
基于禧泰数据库的全国城市二手房价监测数据,利用描述统计和GIS空间分析方法详细分析了2011—2018年126个中国资源型城市房价时空变化特征,并采用空间杜宾模型进一步揭示了其影响因素。研究结果表明:(1)2011年和2018年中国资源型城市平均房价分别为4105元/m2和5675元/m2,再生型城市、成熟型城市、成长型城市和衰退型城市的平均房价依次递减;(2)2011—2018年中国资源型城市平均房价呈现出波动上升的态势,房价增长率为38.2%,远低于全国城市平均房价增长幅度55.3%,且不同类型资源型城市房价的增长幅度有所差异,以成熟型和再生型城市的房价增幅相对较大;(3)中国资源型城市房价和变化存在显著的空间集聚特征,房价热点区主要集中在东部地区和中部地区城市,房价冷点区主要以东北地区和西部地区城市为主;(4)空间杜宾模型显示,人均GDP、人均住房开发投资、多样化指数、专业化指数和工业废水排放强度是影响中国资源型城市房价空间差异的主要因素。 相似文献
163.
闽三角地区碳排放时空差异及影响因素研究 总被引:1,自引:0,他引:1
以闽三角地区为研究对象,以2005~2017年为研究期,构建城市尺度的碳排放清单,应用对数平均迪氏指数分解方法从时间维度的纵向比较和典型年份城市横向比较两个维度开展了驱动因素的分解分析及评价,探讨了闽三角碳排放变化影响因素的时空差异.结果显示:研究期内闽三角CO2排放增长较快,从2005年的74.08Mt增加到2017年169.48Mt,增幅为128.75%.其中,泉州贡献最大,占比为67.93%.碳排放变化趋势分析来看,产业结构和经济增长为导致闽三角地区碳排放量增长的主要因素,累计贡献度分别为30.38%和12.21%,能源结构为抑制碳排放的重要影响因素,累计贡献度为-45.76%.时空差异上看,能源结构效应在研究期内均表现为抑制效应,最大贡献率为52.95%;而产业结构效应均表现为促进效应,最大贡献率为33.85%.在研究期内,漳州市碳减排力度最大,最大净减排148.27Mt.而泉州市经济增长和产业结构效应贡献率较大,未来仍具有较大的减排空间.厦门市经济增长和产业结构效应贡献率均低于参考值,且在研究期内变动幅度较小,碳减排压力较低.研究结果深化了闽三角地区碳排放的时空格局及影响因素的科学认识,为闽三角地区及相似城市群的减排治理提供了有益借鉴. 相似文献
164.
Shouliang Huo Chunzi M Beidou Xi Yali Zhang Fengchang Wu Hongliang Liu 《环境科学学报(英文版)》2018,30(5):54-66
Nutrient criteria provide a scientific foundation for the comprehensive evaluation, prevention,control and management of water eutrophication. In this review, the literature was examined to systematically evaluate the benefits, drawbacks, and applications of statistical analysis,paleolimnological reconstruction, stressor-response model, and model inference approaches for nutrient criteria determination. The developments and challenges in the determination of nutrient criteria in lakes and reservoirs are presented. Reference lakes can reflect the original states of lakes, but reference sites are often unavailable. Using the paleolimnological reconstruction method, it is often difficult to reconstruct the historical nutrient conditions of shallow lakes in which the sediments are easily disturbed. The model inference approach requires sufficient data to identify the appropriate equations and characterize a waterbody or group of waterbodies, thereby increasing the difficulty of establishing nutrient criteria. The stressor-response model is a potential development direction for nutrient criteria determination, and the mechanisms of stressor-response models should be studied further. Based on studies of the relationships among water ecological criteria, eutrophication, nutrient criteria and plankton, methods for determining nutrient criteria should be closely integrated with water management requirements. 相似文献
165.
IntroductionThe evaluation of head protection systems needs proper knowledge of the head impact conditions in terms of impact speed and angle, as well as a realistic estimation of brain tolerance limits. In current bicycle helmet test procedures, both of these aspects should be improved. Method: The present paper suggests a bicycle helmet evaluation methodology based on realistic impact conditions and consideration of tissue level brain injury risk, in addition to well known headform kinematic parameters. The method is then applied to a set of 32 existing helmets, leading to a total of 576 experimental impact tests followed by 576 numerical simulations of the brain response. Results: It is shown that the most critical impacts are the linear-lateral ones as well as the oblique impact leading to rotation around the vertical axis (ZRot), leading both to around 50% risks of moderate neurological injuries. Based on this test method, the study enables us to compare the protection capability of a given helmet and eventually to compare helmets via a dedicated rating system. 相似文献
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从大气环境、噪声与土壤环境、水环境和生态、安全与可持续4个方面构建页岩气开发环境影响指标体系,并建立基于熵权法和云模型评价法的页岩气环境影响评价模型。针对四川省某国家级页岩气示范区进行实证分析,结果表明:该地区页岩气开发环境影响处于中等程度。页岩气开发对水环境影响最大,其次是对大气环境的影响,再次是对噪声与土壤环境,对生态、安全与可持续方面影响相对最小。该模型的评价结果与页岩气开发环境影响现状相符,最后根据评价结果提出相关政策建议。 相似文献
170.
Statistical prediction is a tool and aim in ecology and wildlife management and conservation. A prediction may either be supported by or contradicted by observations of an unknown set of observations. A contradiction occurs if the prediction is not included within the range of the unknown observations, i.e. the prediction misses the cloud of observations completely. Mixed-effects models, frequently used for statistical assessment of clustered data, carry information needed for calculating the probability of such contradictions. Here we present a new versatile statistic, the probability of contradiction (P (Contra)), that describes how often we would anticipate a new cluster of observations contradicting our predictions. Some benefits of P (Contra) are: (1) easy to calculate and intuitive interpretation, (2) comparability between datasets, (3) inclusion of residual correlation, (4) summary of the multitude of information from mixed models into one statistics, and (5) applicable to local mixed-effect models. 相似文献