The statistical analyses of flares detected in B band photometry of UV Ceti type stars

In this study, we present the unpublished flare data collected from 222 flares detected in the B band observations of five stars and the results derived by statistical analysis and modeling of these data. Six basic properties have been found with a statistical analysis method applied to all models and analyses for the flares detected in the B band observation of UV Ceti type stars. We have also compared the U and B bands with the analysis results. This comparison allowed us to evaluate the methods used in the analyses. The analyses provided the following results. (1) The flares were separated into two types, fast and slow flares. (2) The mean values of the equivalent durations of the slow and the fast flares differ by a factor of 16.2 ± 3.7. (3) Regardless of the total flare duration, the maximum flare energy can reach a different Plateau level for each star. (4) The Plateau values of EV Lac and EQ Peg are higher than the others. (5) The minimum values of the total flare duration increase toward the later spectral types. This value is called the Half-Life value in models. (6) Both the maximum flare rise times and the total flare duration obtained from the observed flares decrease toward the later spectral types.     

Finding the most appropriate precipitation probability distribution for stochastic weather generation and hydrological modelling in Nordic watersheds

Six precipitation probability distributions (exponential, Gamma, Weibull, skewed normal, mixed exponential and hybrid exponential/Pareto distributions) are evaluated on their ability to reproduce the statistics of the original observed time series. Each probability distribution is also indirectly assessed by looking at its ability to reproduce key hydrological variables after being used as inputs to a lumped hydrological model. Data from 24 weather stations and two watersheds (Chute‐du‐Diable and Yamaska watersheds) in the province of Quebec (Canada) were used for this assessment. Various indices or statistics, such as the mean, variance, frequency distribution and extreme values are used to quantify the performance in simulating the precipitation and discharge. Performance in reproducing key statistics of the precipitation time series is well correlated to the number of parameters of the distribution function, and the three‐parameter precipitation models outperform the other models, with the mixed exponential distribution being the best at simulating daily precipitation. The advantage of using more complex precipitation distributions is not as clear‐cut when the simulated time series are used to drive a hydrological model. Although the advantage of using functions with more parameters is not nearly as obvious, the mixed exponential distribution appears nonetheless as the best candidate for hydrological modelling. The implications of choosing a distribution function with respect to hydrological modelling and climate change impact studies are also discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

HadCM3模式下钱塘江流域设计暴雨估算

全球气候变化背景下,极端水文气象事件发生的频率和强度都受到了直接影响,研究气候变化对极端水文气象事件的影响对防灾减灾和工程设计等至关重要.采用了联合国政府间气候变化专门委员会(IPCC)第四次评估报告中给出的A1B、A2和B1三种温室气体排放情景,选用大气环流模式Had-CM3,利用随机天气发生器LARS-WG生成逐日气象资料,结合P-Ⅲ型曲线和线性矩方法分析计算了钱塘江流域21世纪中叶的设计暴雨情况.结果表明:LARS-WG天气发生器在钱塘江流域有较好的模拟效果;在A1B和B1情景下,钱塘江流域各站点不同重现期下的设计暴雨值基本呈增大趋势,其中A1B情景下杭州站百年一遇的设计暴雨值为209.14mm,比基准期增大11.0％.     

云南省地震与太阳活动的统计关系研究

地震与太阳活动的关系是研究活动性和地震预测中有意义的课题。作者选取云南省及周边地区1965～2006年2级以上地震为样本,使用时间序列分析方法和相关分析方法对地震与太阳黑子、耀斑的相关性进行了研究,得到中小地震为主的样本与太阳活动不相关、大地震与太阳活动存在弱相关性的结论。作者的结论与以往研究者的结论不同,原因在于以往的研究者使用大震强震为样本,样本数少,得到的结论存在不可避免的偶然性。因此在一个地方具备发生大地震的内在条件时,关注太阳活动也是十分必要的。     

华北北部地区地震与太阳活动关系的统计研究

使用时间序列分析和相关分析方法,分析华北北部地区1970～2006年地震与太阳黑子、耀斑的相关性,得到的结论是,太阳活动与以中小地震为主的地震样本不存在统计关系。这个结论与以往的研究不同,本文对此做了初步分析。     

中国天气发生器降水模拟参数的气候变化特征

利用中国672个站点1951-2007年的逐日降水资料,分1951-1978和1979-2007两个时段分析了中国天气发生器BCC/RCG-WG降水模拟参数的气候变化特征.结果表明,在气候变化背景条件下,我国各地干日到湿日的降水转移概率P(WD)和湿日到湿日的降水转移概率P(WW)除了西部部分地区有增大的趋势外,其余大部地区均有减小的趋势.相对于P(WW),全国各地P(WD)的减小幅度更大.日降水量GAMMA分布形态参数ALPHA除西北地区西部部分地区有减小趋势外,其余大部地区略有增大趋势,尺度参数BETA在全国各地基本都保持增大的趋势,其中西北地区西部等地增大趋势尤为明显.相对于BETA的变化幅度,ALPHA的减小幅度较小,基本在6%以内.     

黄河上游河曲地区对流云催化增雨的数值模拟研究

应用中国科学院大气物理研究所开发的三维对流云模式,对青藏高原河曲地区强对流云的催化增雨效果及催化云的动力特征、微物理机制进行了模拟研究.模拟结果显示:黄河上游河曲地区的对流云具备一定的催化潜力.如果催化时机、部位选择适当,降水总量增加有望达到30%～50%,催化所产生的动力效果比较显著.催化剂的加入使得云中凝华潜热释放量增加,上升气流加强,云顶升高,云水平尺度也有所加大,地面降水区域扩大,降水时间延长.由于云中冰晶大量生成,导致过冷云水、雨水减少,暖雨过程迅速减弱,云中霰和冻滴量增多,其融化过程加强引起的降水增加远远超过了暖雨量的减少,总的增雨效果比较显著.敏感性实验表明,催化高度对增雨效果的影响最为显著,高于某一催化高度,有可能产生增雨防雹的好效果;低于某一催化高度,则会在防雹的同时使地面降水减少.对流云早期催化的增雨效果较好.一定范围内催化剂量的变化对增雨量影响不大,小剂量催化也有可能达到较好的增雨效果.     

中国天气发生器的降水模拟

A stochastic model for daily precipitation simulation in China was developed based on the framework of a ‘Richardson-type‘ weather generator that is an important tool in studying impacts of weather/climate on a variety of systems including ecosystem and risk assessment. The purpose of this work is to develop a weather generator for applications in China. The focus is on precipitation simulation since determination of other weather variables such as temperature is dependent on precipitation simulation. A framework of first order Markov Chain with Gamma Distribution for daily precipitation is adopted in this work. Based on this framework, four parameters of precipitation simulation for each month at 672 stations all over China were determined using daily precipitation data from 1961 to 2000. Compared with previous works, our estimation for the parameters was made for more stations and longer observations, which makes the weather generator more applicable and reliable. Spatial distributions of the four parameters are analyzed in a regional climate context. The seasonal variations of these parameters at five stations representing regional differences are discussed.Based on the estimated monthly parameters at 672 stations, daily precipitations for any period can be simulated. A 30-year simulation was made and compared with observations during 1971-2000 in terms of annual and monthly statistics. The results are satisfactory, which demonstrates the usefulness of the weather generator.     

新型氢化物发生技术—可移动还原床氢化物发生器：Ⅱ.干扰及其应用

新型的氢化物发生技术－可移动还原床氢化物发生器可以实现微升级样品的测定而不需要对样品进行酸化和使用气－液分离器。应用ＭＲＢＨＧ－电感耦合等离子体发射光谱取得了同等质量的而不同形态的Ａｓ,Ｓｅ的相同信号强度,证明了在ＭＲＢＨＧ体系中氢化物元素之间的干扰得到消除,方法用于合金钢,富硒茶叶等实际样品的测定,标准加入的回收率在９３％－１１４％。     

XP-2型弦式通用频率计

该仪器是测压振弦式传感器的二次仪表,与振弦式传感器配合使用,已广泛地用于水利、电力、交通等部门建筑物的测量与安全监测,也在围垦工程的海堤施工和安全监测中获得应用。该仪器不仅能用于测量与安全监测,也能对各种型号的振弦式传感器进行调试标定,还能对直读式弦式频率计进行计量校验。