Flood estimation in Mahanadi river system,India using partial duration series

Flood frequency analysis is a pre-requisite for setting up and safeguarding of many hydraulic structures, such as dams, barrages, check-dams, culverts and urban drainage systems. In the flood frequency analysis, partial duration series (PDS) may be considered when dealing with values exceeding certain limits causing floods. In fact, the PDS is capable of getting more information about extreme events than the annual maximum series (AMS). Additionally, an assumption that, the magnitude of the extreme events of a PDS is best described by a generalized Pareto (GP) distribution. The present work investigates the at-site flood frequency analysis to find the average number of peaks (λ) for modelling the PDS on the basis of the PDS/GP assumption and variability in the GP parameters coupled with the quantile estimation with an increase in the value of average number of peaks (λ) each year in the Mahanadi river system, Odisha, India. Also, to verify the PDS/GP assumption we tested seven different frequency distributions (Exponential, Gumbel, logistics, generalized extreme value (GEV), Lognormal (LN), generalized logistics (GL) and Pearson Type 3). Extensive daily discharge data collected from 23 gauging sites were used for the analysis. The results indicate precision and stability of GP distribution parameters for λ?=?4 for almost all the discharge sites. The peak flood estimated for various return periods in the Mahanadi river system using GP distribution is endowed with high correlation statistics for this λ value.     

黄海水温与沙海蜇丰度年际变化的相关分析

近十年来,我国黄、东海沙海蜇的数量呈上下波动趋势,除2008、2010、2011、2013年为不暴发年外,其余年份均为暴发年或弱暴发年(本文界定沙海蜇平均丰度范围为2—10ind./100m2为暴发年,1—2ind./100m2为弱暴发年,0—1ind./100m2为不暴发年)。为研究沙海蜇数量年际变化的原因,本文借助同化的海洋模式结果,分析了2006—2013年南黄海沙海蜇平均丰度与表底层海水温度的关系、与不同温度持续时间的关系。研究结果发现,在海州湾附近,对于暴发年2007年和2009年,春季底层海水10—18°C持续时间为130天,比不暴发年2010年和2011年多近15天。在长江口区域,不暴发年2008年和2011年夏秋季底层海水18—25°C持续时间较长,约80天,比暴发年2007年多20天。在长江口、苏北近岸以及海州湾区域,春季底层海水10—18°C持续时间越长,南黄海水母丰度呈现越大的趋势;夏秋季底层海水18—25°C持续时间越长,第二年水母生物量则越大。结果支持和验证了春季底层10—18°C持续时间长有利于当年水母暴发及夏秋季底层18—25°C持续时间长有利于来年水母暴发的推论。本文通过分析沙海蜇丰度和温度变化的关系,可以为将来预测该水母数量提供基础。     

Different sperm allocation strategies in two populations of the semiterrestrial crab Neohelice granulata (Brachyura,Grapsoidea, Varunidae)

Sperm reserves are costly to produce and so the development of different sperm allocation strategies may be advantageous. Knowledge of sperm allocation strategies is important from an evolutionary perspective because they contribute to characterize mating systems. However, population differences in sperm allocation strategies of the same species have rarely been assessed. Here, we studied the male sperm allocation strategies in two different populations of Neohelice granulata in Mar Chiquita Lagoon (MCL) and San Antonio Oeste (SAO), Argentina. We found that the quantity of ejaculate transferred by N. granulata males depended on different factors such as male size and female receptivity duration, while it was independent of female size, at both study areas. Regarding the operational sex ratio factor, the amount of ejaculate transferred depended on it in MCL but not in SAO. Thus, N. granulata males may have the capacity to regulate the quantity of ejaculate transferred based on individual factors such as their own size and female receptivity duration, and population factors such as operational sex ratio, which varies in the two populations studied.     

近50年甘肃日照时数时空变化特征及突变分析

利用甘肃省26个气象站1961—2010年逐月日照时数资料,采用线性趋势分析、异常年份分析、Mann-Kendall和功率谱等方法,分析了日照时数的时空变化及突变特征.结果表明:50年来,甘肃年日照时数表现为缓慢的下降趋势,气候倾向率为-0.29 h·(10 a)^-1,1997年以来显著减少;夏、冬季日照时数呈下降趋势,春、秋季则呈增加趋势;年日照时数异常偏少年份主要出现在20世纪80年代,而异常偏多的年份多发生在20世纪90年代至今;甘肃年日照时数空间差异明显,分布趋势基本上呈由东南向西北逐渐增多形势.Mann-Kendall和Yamamoto突变检验表明,四季日照时数未发生显著突变.周期分析表明,甘肃年日照时数存在2 a的振荡周期,通过了90%置信度检验.     

Correlation between petrographic characteristics and failure duration in clastic rocks

Being the inherent attributes of rock, the petrographic characteristics such as mineral composition and microstructure are the constructive parameters which influence its bursting potential. In the laboratory, rock specimens with different petrographic characteristics are tested to study their rock strength and failure duration, and correspondingly, composition and microstructure of each rock specimen are analyzed in thin sections to determine the mineral composition, content, grain size, cement and contact modes between grains. The results show that the petrographic characteristics of clastic rock have an intrinsic influence on its strength and failure duration. With the increase of the rock detritus content (or quartz), the uniaxial compressive strength increases according to a logarithmic expression and the failure duration decreases according to a negative logarithmic expression. With increasing average size of detritus grains in rock, the stiffness and brittleness of rock strengthens. The uniaxial compressive strength of rock has a logarithmic variation with its average size of detritus grains and the failure duration decreases with its increasing average size of detritus grains according to a negative logarithmic expression.     

防火墙在陕西气象信息网络中的应用

本文利用ENSO事件资料，结合吕梁地区1957年至2000年汛期(6月至8月)降水资料，分析了ENSO事件影响年的汛期降水特征，得出了ENSO事件起始季节、强度、持续时间与吕梁汛期降水的关系是密切的。     

Comparative evaluation of Poisson partial duration models for mixed flood populations

Simple homogeneous formulations of two extreme value partial duration flood models are compared to more sophisticated compound formulations in terms of asymptotic performance of quantile estimates. The compound model formulations were developed to model flood series resulting from mixed climatological processes. It was found that only in the case of marked nonhomogeneity in the data samples did the compound formulation of the models offer significant advantages in terms of variance of quantile estimates. However, the estimates from the homogeneous model were significantly biased in the negative direction. This negative bias of quantile estimates from the simple model was even more pronounced when the more sophisticated Weibull model was used as the base.     

Microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory observation of near-fault high-frequency strong motion

High-frequency velocities are measured during stick-slip motion in the immediate vicinity of a fault in a granite sample to reveal the microscopic process taking place in the breakdown zone defined in the slip-weakening model. It is found that 1) the onset time of the observed strong motion approximately coincides with the local rupture onset time, 2) the observed near-fault high-frequency strong-motion duration is approximately proportional to the local breakdown time, and 3) the power spectra of strong motions exhibit significant amplitudes at frequencies above the value off _max, wheref _max is a cut-off frequency relevant to rupturing the breakdown zone. These observations suggest that the high-frequency motion would be due to the incoherent brittle microfracture whose characteristic scale is much shorter than the breakdown zone size. We present a stochastic fault model to synthesize the near-fault high-frequency velocity waveforms. In the model, a number of small circular subfaults are distributed randomly on the fault and the rupture onset time of an individual subfault is assumed to be random. The main features of the observed velocity waveforms are well explained by this numerical modeling. It is concluded that approximately half of the total energy of high-frequency elastic waves observed at a point is radiated from the propagating breakdown zone. We emphasize the importance of the observation of near-fault high-frequency strong motions for large shallow earthquakes.     

辽宁省及邻近地区较大地震震级的测定方法

本文使用１９８６年至１９９１年期间沈阳遥测地震台网记录到的１４５３次地震的持续时间资料（２．０≤Ｍ＿Ｌ≤６．１级、５ｋｍ＜△＜１０００ｋｍ），求得了辽宁省及其邻近地区多台多幅度持时震级的经验公式，结果表明，这种震级误差小，应用范围为Ｍ＿Ｌ≤６．０级，解决了限幅地震无法计算震级的难题．     

PARTITION OF SEASON BASED ON MULTIELEMENTS AND THE DECADAL CHANGE OF SEASON DURATION IN CHINA

Using the multielements similarity measurement method and 1950–2017 NCEP/NCAR gridded daily reanalysis datasets, we analyzed season duration in China during 1950–2016, and we defined the element with maximum absolute sensitivity as the key impact element at each point using the sensitivity analysis method. The decadal change of season duration and its key impact element before and after 1980 were studied. The results indicated obvious meridional and zonal differences in the distribution of season duration for the 67-year average, and that the key impact element has the same distribution characteristics as season duration. In addition, complementary relationships were found between the durations of spring and summer, autumn and winter, and the cold and warm seasons. Of those, the complementary relationship between the durations of spring and summer was strongest and the regions of complementarity were numerous. The complementary regions of autumn and winter durations were found mainly in western China. In the cold and warm seasons, the complementary regions were widespread and the complementary relationship was generally weak. Comparison of the periods before and after 1980 revealed an east–west difference in the interdecadal variation of season duration. Interdecadal variation in spring and summer was found concentrated in northern and western regions, while that in autumn and winter was concentrated in the western region. Areas of significant interdecadal variation of the key elements were found concentrated in northern and western regions, corresponding well with the areas of significant interdecadal variation of season duration.