重庆地面最高气温与最大风速年极值的渐近分布

利用重庆1951-1990年间地面最高气温和1956-1990年间地面最大风速年极值的记录,采用韦伯分布和耿贝尔分布分别对其渐近分布进行拟合.通过统计推断,找出重庆地面最高气温和地面最大风速年极值遵循的最佳渐近分布--韦伯分布.     

Rainfall flood hazard at nuclear power plants in India

Flood hazard evaluation is an important input for Nuclear Power Plants external events safety studies. In the present study, flood hazard at various nuclear sites in India due to rainfall has been evaluated. Hazard estimation is a statistical procedure by which rainfall intensity versus occurrence frequency is estimated from historical records of rainfall data and extrapolated with asymptotic extreme value distribution. Rainfall data needed for flood hazard assessment are daily annual maximum rainfall (24?h data). The observed data points have been fitted using Gumbel, power law and exponential distribution, and return period has been estimated. To study the stationarity of rainfall data, a moving window estimate of the parameters has been performed. The rainfall pattern is stationary in both coastal and inland regions over the period of observation. The coastal regions show intense rainfall and higher variability than inland regions. Based on the plant layout, catchment area and drainage capacity, the prototype fast breeder reactor (PFBR) site is unlikely to be flooded.     

用Gumbel极值分布推算气候极值的方法

介绍了用Gumbel极值分布理论推算气候极值的矩法、Thomas曲线公式和最小二乘法。并计算多年一遇的年最高气温、年最大均风速、年最大日降雨量和年最大波高。指出,变率小的要素极值再现期短;变率大的要素极值再现期长;Thomas曲线公式的计算结果较其它两种方法接近历史实况,且计算简便。     

Seismic hazard assessment using intensity point data

The influence of the attenuation model used in seismic hazard assessment in terms of intensity and acceleration is studied. For two sites in central Italy, the catalogue of the actual observed intensities during the last three centuries has been recovered. In the study region, the data collected during a recent seismic sequence give the basis for relating intensity and acceleration. The results show the importance of establishing statistical relationships among the used quantities, based on a representative set of data.     

Extreme Earthquake and Earthquake Perceptibility Study in Greece and its Surrounding Area

The sample interval for the selection of extreme magnitudes plays an important part in the quality of Gumbel model fitting. A short sample interval can produce many observations, which is helpful in obtaining a reliably fitting model. However a short sample interval can bring many dummy ``observations', a condition which adversely biases the fitting. The short sample interval also increases the chance to introduce non-independent observations as well, which violates a basic requirement of the Gumbel model. On the other hand, a large time interval not only reduces the number of observations, but also enlarges the observation error. Thus, for Greece, the most suitable parameters of the third Gumbel extreme model are obtained by using a sample interval which produces minimum error. In consideration of the reliability of the seismic data, earthquakes with magnitude M 5.5 in Greece and its surrounding region after 1900 are used mainly in the present paper. In order to obtain well resolved contour maps with smooth changes a 2°× 2° cell with half-degree overlap strategy was used to scan the region. The most expected largest earthquake for the next fifty, one hundred and two hundred years are estimated for each cell. Likewise, the events with magnitude at a probability of 90\% of non-exceedance over the next fifty, one hundred and two hundred years are estimated for each cell. In parallel to this procedure we also analyze the 67 shallow seismic zones outlined by Papazachos and his colleagues and detail individual zone results where these are obtained. The most perceptible earthquake magnitude for the range of intensities I = {VI}, VII and VIII are also calculated. All results show that the areas around the Hellenic Arc and the Cephalonia Transform Fault for Greece have comparatively high frequency of destructive earthquakes accompanied by a high occurrence probability of moderate earthquakes (M 5.5).     

珠江三角洲地区风暴潮重现期及增水与环境要素的关系

珠江三角洲地区是我国海岸中台风暴潮最严重的区域之一,受全球变暖和海平面上升影响,该地区风暴潮增水重现值将出现显著的变化。本文采用耿贝尔方法和皮尔逊Ⅲ型分布法,分别计算了珠江三角洲地区11个潮位站的最大增水值的重现期,并对计算结果进行了比较,绘制了风暴潮增水重现值分布曲线。结果表明大部分潮位站的耿贝尔分布曲线与经验频率点吻合程度较好,少数潮位站的皮尔逊Ⅲ型分布曲线与经验频率点吻合程度较好,两种方法结合起来效果最佳;分析了该地区风暴潮重现期的基本特征;最后总结了风暴潮与台风路径、天文潮以及地形之间的关系。该计算结果将为政府规划设计部门决策提供参考,对风暴潮预报、海岸工程设计和估计风暴潮造成的损失提供科学依据。     

Statistics of extremes and estimation of extreme rainfall: II. Empirical investigation of long rainfall records / Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: II. Recherche empirique sur de longues séries de précipitations

Abstract

Abstract In the first part of this study, theoretical analyses showed that the Gumbel distribution is quite unlikely to apply to hydrological extremes and that the extreme value distribution of type II (EV2) is a more consistent choice. Based on these theoretical analyses, an extensive empirical investigation is performed using a collection of 169 of the longest available rainfall records worldwide, each having 100–154 years of data. This verifies the theoretical results. In addition, it shows that the shape parameter of the EV2 distribution is constant for all examined geographical zones (Europe and North America), with value κ = 0.15. This simplifies the fitting and the general mathematical handling of the distribution, which become as simple as those of the Gumbel distribution.     

Spatial mapping of earthquake hazard parameters in the Hindukush–Pamir Himalaya and adjacent regions: Implication for future seismic hazard

The study deals spatial mapping of earthquake hazard parameters like annual and 100-years mode along with their 90% probability of not being exceeded (NBE) in the Hindukush–Pamir Himalaya and adjoining regions. For this purpose, we applied a straightforward and most robust method known as Gumbel’s third asymptotic distribution of extreme values (GIII). A homogeneous and complete earthquake catalogue during the period 1900–2010 with magnitude M_W ⩾ 4.0 is utilized to estimate these earthquake hazard parameters. An equal grid point mesh, of 1° longitude X 1° latitude, is chosen to produce detailed earthquake hazard maps. This performance allows analysis of the localized seismicity parameters and representation of their regional variations as contour maps. The estimated result of annual mode with 90% probability of NBE is expected to exceed the values of M_W 6.0 in the Sulaiman–Kirthar ranges of Pakistan and northwestern part of the Nepal and surroundings in the examined region. The 100-years mode with 90% probability of NBE is expected to exceed the value of M_W 8.0 in the Hindukush–Pamir Himalaya with Caucasus mountain belt, the Sulaiman–Kirthar ranges of Pakistan, northwestern part of the Nepal and surroundings, the Kangra–Himanchal Pradesh and Kashmir of India. The estimated high values of earthquake hazard parameters are mostly correlated with the main tectonic regimes of the examined region. The spatial variations of earthquake hazard parameters reveal that the examined region exhibits more complexity and has high crustal heterogeneity. The spatial maps provide a brief atlas of the earthquake hazard in the region.     

On the Characteristics of Heavy Multiple-Day Snowfalls in the Eastern Alps

Based on the daily fresh-snowrecordings of a set of 81 stations of the AustrianHydrographic Service, covering a 19-year period,various aspects of extraordinarily long-lasting severesnowfalls are investigated. Starting from an exactdefinition of periods of Heavy Snowfall Events (HSE),some of the discussed items include the annual andseasonal frequencies of intense snowfall episodes, thelocation and migration paths of the storm centers andthe volume of snow dropped by the individual storms.Another part of the study, designed to visualize thebig variability of snow-related parameters over Alpineterrain, determines for all involved sites maximalobserved and theoretical extreme fresh-snowaccumulations for periods of variable length. Heavythree-day snowfall events are analyzed with specialregard of the resulting avalanche threat.     

我国东部极端降水时空分布及其概率特征

利用我国105°E以东地区210个测站近50年(1953—2002年)逐日降水资料,在REOF客观分区的基础上,确定各分区的极端降水最佳采样期为1~2日。进而研究了日极端降水量的气候特征。采用具有优良特性的L-矩参数估计方法对我国东部极端降水拟合Gumbel分布。结果表明,L-矩参数估计方法的拟合优度比其它方法有进一步提高,近50年来,极端降水趋势虽无明显变化,但其时空差异较大。符合Gumbel分布的极端降水重现期的地理空间分布,大致特征是,东南大、西北小,两湖盆地、黄海海湾及辽东半岛也有高值区。