基于信息熵理论的黄土高原小流域雨量站网优化

地面雨量站是降水数据最直接的来源,合理的雨量站点密度与空间布局能准确反映流域面雨量,对于构建流域水文模型至关重要.以黄土高原岔巴沟流域为研究对象,采用2001—2010年流域内11个地面雨量站的日、周、15 d时间尺度降雨量序列,以信息熵理论为基础,基于最大信息最小冗余准则(MIMR),分析11个地面雨量站之间降雨的信...     

森林植被变化对潜山流域径流量的影响

采用流域自身对比法,利用潜山流域水文站实测的44 a降雨量—径流量数据,定量分析了该流域降雨量—径流量变化关系.选择1987年、1999年和2007年3个典型年份,结合植被覆盖度分级图,定量分析研究了大别山地区潜山流域森林植被变化对该区域森林水源涵养关系的影响.研究发现,2007年低植被覆盖区比1987年减少56%,中植被覆盖区比1987年增加12%,高植被覆盖区比1987年增加24%,2007年平均降雨量较1987年减少52%,而平均径流量较1987年减少69%,表明森林覆盖率提高能减少径流,显著降低径流系数,增强流域抗洪能力,使得森林水源涵养能力得到提升.     

义乌降水气候分析中的面雨量计算及其应用比较

用区域面雨量的泰森多边形法计算方法,并与算术平均法和气象站单站资料在气候变化分析中的应用进行比较,发现泰森多边形法与算术平均法计算的面雨量差别较小,而与气象站单站资料比较,其差异相当明显;认为某单站降水资料不能代表该区域降水量,在降水气候分析或某区域降水量趋势预报中,用泰森多边形法计算的面雨量比算术平均法更科学、简便、合理．     

双超模型在半湿润地区的应用

中国北方多属半干旱、半湿润地区,其降雨径流的形成过程较为复杂,既有蓄满产流,又有超渗产流,针对这种产流现象,分析其物理机制,在前人研究的基础上,探讨了适用于超渗产生地表径流、超持产生壤中流的＂双超＂产流模型和汇流模型,并将其应用于文峪河流域,进行了洪水模拟应用,研究结果表明,洪水过程的模拟预测结果与实测结果基本吻合;对于不同年份降雨的洪水模拟,除少数敏感的模型参数外,其它模型参数几乎不变,说明该模型弹性较好,因此该模型在这类地区具有较强的适用性和实用性。     

降雨输入对青龙河流域HSPF模型模拟结果的影响

为评价降雨输入对青龙河流域BASINs/HSPF模型模拟结果的影响,改善HSPF模型模拟精度,应用趋势成分建模、周期成分建模、相依随机建模和独立随机建模（白噪声）等随机建模程序和蒙特卡洛计算机模拟方法,获得200组降雨随机模拟序列,分别作为青龙河流域BASINs/HSPF模型的输入,以Nash-Sutcliffe效率系数（E_NS）作为模型模拟效果的评价标准,获得如下结论:采用趋势成分、周期成分与ARMA建模以及正态随机模拟获得降雨随机模拟序列是量化降雨输入随机性的可行方法;在模型参数优化的条件下,降雨随机模拟序列HSPF模拟E_NS值的变化区间为[71.09%,74.96%],波动幅度达3.87%,表明降雨输入随机性对于HSPF模拟结果具有显著影响;当考虑每年的日降雨量极大值时,E_NS值变化区间为[75.35%,78.81%],波动幅度达3.46%,且结果均优于没有考虑降雨极大值点的降雨随机模拟序列,表明降雨时间序列的极大值点对于HSPF模拟效果具有显著影响;随着降雨时间序列中所考虑极大值点数量的逐渐增多,HSPF模拟效果出现下降趋势,表明HSPF模拟应特别关注若干最大极值点的影响;降雨输入的不确定性是HSPF模型模拟结果不确定性的重要来源,改善HSPF模拟效果需要考虑降雨时间序列随机性和极值点因素的影响.本研究可为量化降雨输入对HSPF模型模拟的影响以及HSPF模拟的降雨情景优选提供借鉴.     

雨雪天气下特高压交流单回试验线段电晕损失实测分析

为了研究特高压交流输电线路在雨天、雪天气象条件下的电晕损失特性,基于我国特高压交流试验基地单回试验线段展开实测研究,采用研制的光电数字化输电线路电晕损失监测系统,实现了试验线段电晕损失全天候条件下实时在线测量,根据监测结果分析不同降雨率及大雪气象条件下电晕损失。研究结果表明,正常运行电压下,特高压交流单回试验线段雨天单相单位长度电晕损失约为20～60 W/m,在大雪气象条件下,根据监测结果,特高压交流单回试验线段单位长度电晕损失最大值为:边相达到53.54 W/m,中相达到62.95 W/m,与等值降雨率推算结果较为符合。电晕损失随降雨率增大呈非线性增长,在大雨条件下逐渐趋于饱和,并初步获得8×LGJ-500/35分裂导线降雨率与电晕损失拟合模型。该试验获得的特高压交流单回试验线段电晕损失实测结果,为特高压交流输电线路导线选型设计及运行经济性衡量提供了参考。     

基于ECMWF和WRF的嘉陵江流域面雨量预报精度评估

将降雨数值预报产品运用到水文预报中已经逐渐成为提高洪水作业预报的预见期的重要手段。为充分了解ECMWF(European Centre for Medium Range Weather Forecasts)和WRF(Weather Research and Forecasting model)2种数值天气预报产品对嘉陵江研究区面雨量预报的预报精度和误差分布,且为增强洪水预报精度的稳健性提供科学支持,采用TS评分、空报率、漏报率、正确率等指标,对嘉陵江地区7个气象分区内的2016年汛期面雨量预报结果进行了检验,分析了不同分区内各检验指标与预报时效的关系。结果表明:ECMWF数值预报产品和WRF数值预报产品均可用于该地区晴雨预报,且2种产品的预报精度随降水等级的增大呈增大趋势,随预报时效的增加呈减小趋势。综合而言,ECMWF数值预报产品对嘉陵江研究区的预报效果更好。     

Climate Change and Future Long-Term Trends of Rainfall at North-East of Iraq

Iraq is facing water shortage problem despite the presence of the Tigris and Euphrates Rivers. In this research, long rainfall trends up to the year 2099 were studied in Sulaimani city northeast Iraq to give an idea about future prospects. The medium high （A2） and medium low B2 scenarios have been used for purpose of this study as they are more likely than others scenarios, that beside the fact that no climate modeling canter has performed GCM （global climate model） simulations for more than a few emissions scenarios （HadCM3 has only these two scenarios） otherwise pattern scaling can be used for generating different scenarios which entail a huge uncertainty. The results indicate that the average annual rainfall shows a significant downward trend for both A2 and B2 scenarios. In addition, winter projects increase/decrease in the daily rainfall statistics of wet days, the spring season show very slight drop and no change for both scenarios. However, both summer and autumn shows a significant reduction in maximum rainfall value especially in 2080s while the other statistics remain nearly the same. The extremes events are to decrease slightly in 2080s with highest decrease associated with A2 scenario. This is due to the fact that rainfall under scenario A2 is more significant than under scenario B2. The return period of a certain rainfall will increase in the future when a present storm of 20 year could occur once every 43 year in the 2080s. An increase in the frequency of extreme rainfall depends on several factors such as the return period, season of the year, the period considered as well as the emission scenario used.     

Evaluation and optimisation of receiver height in a compound parabolic collector with low acceptance angle

This research presents the method of finding an optimised location of a tubular receiver for a compound parabolic collector (CPC) with 6° acceptance angle. Due to low acceptance angle, reflected rays concentrate below the focus of a parabola. Graphical ray tracing (GRT) approach is implemented to execute the optical analysis with and without manufacturing error in the collector. It is performed on collector–receiver combinations by varying receiver height below the focus and they are compared on the basis of utilised area and projection ratios. The ideal cases of collector–receiver combinations which contribute high utilisation and projection ratio are selected and verified with the camera target method (CTM) performed on the actual set-up. It is built for water heater application to validate the results obtained from GRT and CTM. The thermal performance of CPC at various receiver heights is compared by thermal efficiency and therefore the optimum receiver height is concluded.     

Proposal of a semi-probabilistic approach for storage facility design

Storage facilities are key devices in mitigating the urban drainage impact on receiving water bodies, but their design is still affected by high uncertainty. The analytical-probabilistic approach has recently raised interest, because the facility performances are directly related to probability. Starting from statistically independent storm events, distributions of the meteorological variables must be fitted. Rainfall series, recorded in three Italian raingauges, were examined for appraising two main concerns: the choice of proper probability distributions for rainfall volume and the sample sensitivity with respect to the analysis criterion. The analytical derivation of the model is then finally discussed.