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771.
The urban environment has been dramatically changed by artificial constructions. How the modified urban geometry affects the urban climate and therefore human thermal comfort has become a primary concern for urban planners. The present study takes a simulation approach to analyze the influence of urban geometry on the urban climate and maps this climatic understanding from a quantitative perspective. A geographical building database is used to characterize two widely discussed aspects: urban heat island effect (UHI) and wind dynamics. The parameters of the sky view factor (SVF) and the frontal area density (FAD) are simulated using ArcGIS-embedded computer programs to link urban geometry with the UHI and wind dynamic conditions. The simulated results are synergized and classified to evaluate different urban climatic conditions based on thermal comfort consideration. A climatic map is then generated implementing the classification. The climatic map shows reasonable agreement with thermal comfort understanding, as indicated by the biometeorological index of the physiological equivalent temperature (PET) obtained in an earlier study. The proposed climate mapping approach can provide both quantitative and visual evaluation of the urban environment for urban planners with climatic concerns. The map could be used as a decision support tool in planning and policy-making processes. An urban area in Hong Kong is used as a case study. 相似文献
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北京一次冬季回流暴雪天气过程的数值分析 总被引:6,自引:0,他引:6
回流天气是华北地区冬、春、秋季节产生降雨(雪)的主要天气类型,预报员常常因对回流天气系统结构特征认识不足和诊断失误而导致预报的失败,是降雨(雪)预报的难点和重点。利用北京地区高分辨率快速循环同化中尺度数值预报系统(BJ-RUC)对2010年1月2—3日一次典型的回流暴雪天气过程进行模拟,分析数值模式的模拟能力,研究各层主要影响系统结构特征及形成暴雪的关键性条件,探讨典型回流暴雪天气过程的形成机理。主要结论为:数值模式对此次暴雪过程的近地面回流冷空气、中低层低值系统及变化特征、主要降雪时段和降雪量模拟效果较好,对降雪落区的模拟存在一定偏差。低层回流偏东风遇到地形后引起垂直运动主要在低层800 hPa以下,所产生的降雪量不大,而其与上游850~700 hPa低涡系统发展东移其前部的上升运动汇合所形成的大范围、深厚、强烈的上升运动是产生明显降雪的关键性条件。上游低涡系统前部西南暖湿气流相对应的大湿度区移近是产生较强降雪的重要条件。持续的低层回流冷空气湿度较大,对于低层大气起到水汽输送的作用。回流冷空气使低层大气维持长时间的水汽输送并与其上层东移的大湿度区相结合,增加湿层厚度,有利于降雪持续而形成较强降雪。降雪开始时间和降雪强度的变化与对流层中下转偏南风的时间和偏南风风速增大有关。 相似文献
774.
Papastergiou P Mouchtouri VA Rachiotis G Pinaka O Katsiaflaka A Hadjichristodoulou C 《Marine pollution bulletin》2011,62(3):590-595
Our aim was to examine the health effects on bathers from exposure to recreational seawater on three beaches with different microbiology quality and bather density through a cohort study. An initial questionnaire and a 10 day follow up were used. Univariate and backward logistic regression analyses were used to asses the risk of developing symptoms or diseases among the bathers. In total, 3805 bathers were included in the study and 149 samples were collected from the three beaches. Despite all the beaches being characterized of high quality the levels of bacterial indicators differed among them. Health effects among bathers were not associated with bacterial indicators. A statistically significant increased risk for symptoms related to respiratory illness, gastroenteritis, medical consultation and use of medication was observed among bathers at the higher bather density beaches. Beach bather numbers should always be taken into account when considering a risk assessment approach. 相似文献
775.
Subramani Saravanan Govindan Nagarajan Radhakrishnan Ramanujam Santhanam Sampath 《洁净——土壤、空气、水》2011,39(6):515-521
The main objective of this work is to investigate the factors influencing the NOx control of a stationary diesel engine fuelled with crude rice bran oil blend with lesser effect on smoke density and brake thermal efficiency (BTE). Fuel injection timing, percentage of EGR, and fuel injection pressure are chosen as the factors for the objective and NOx emission, smoke density, and BTE are considered as the response variables. To critically analyze the effects of the chosen factors on the objective three levels were chosen in each factor and the experiments were designed by following the design of experiments method. Taguchi's L9 orthogonal array was used to conduct the tests with different combination of factor levels. Through analysis of variance (ANOVA) method, the most influencing factors and also the significance of each factor affecting each response variable were found out. Response graph was drawn for each response variable to determine the optimum combination of factor levels in achieving the objective and the obtained combination was confirmed experimentally. 相似文献
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对拟建设的新疆且末地磁台进行场址勘选,采取十字剖面测量和密跨度测量方法进行地磁场总强度F测量,对测量结果进行初步分析.分析结果表明,且末地磁台的地质条件、磁场梯度分布和背景噪声环境等地磁观测环境条件,符合国家地磁台建设规范的要求,适宜地磁基准台站建设. 相似文献
779.
弹性各向异性介质岩石体波相速度计算 总被引:1,自引:0,他引:1
蔡晓刚 《地震地磁观测与研究》2011,32(6):80-89
综述弹性波相速度计算的若干严格数值方法和近似解析方法,对数值算例及对不同方法作了比较.结果显示,不同数值方法得到结果一致,其适用于计算任意复杂各向异性介质岩石的相速度,但不便从物理意义的角度去分析物理参数对速度的影响;而近似解析解虽然精确程度各有不同,但是便于从物理意义的角度去进行速度分析,并在此基础上解析求取群速度这... 相似文献
780.
Study on Probability Distributions of Multi-Timescale Aerosol Optical
Depth Using AERONET Data
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The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF. 相似文献