Regional extreme‐dry‐spell frequency analysis using the L‐moments method in the middle reaches of the Yellow River Basin,China

In this research, the regional extreme‐dry‐spell frequency in the middle reaches of the Yellow River Basin (YRB) is studied by the L‐moments method. The research area has been divided into three subregions (regions 1, 2 and 3), which have been identified as homogenous regions. The results of a goodness‐of‐fit test indicate that a generalized normal distribution is the optimal regional model for regions 1 and 2 whereas a generalized Pareto distribution is the optimal regional model for region 3. The return period analysis figures out that the maximum length‐of‐dry‐spell (MxDS) values increase from south to north in the southern part and increase from northeast to southwest in the northern part of the middle reaches of the YRB under different return periods. The increments of quantiles of dry spell under different return levels indicate that drought risk in region 1 is higher than that in regions 2 and 3. The analysis of the occurrence day of MxDS shows that MxDS mostly occurred during winter of 1998 and spring of 1999 in most stations during the considered period. By comparing summer MxDS events, it can be found that mean MxDS values have slightly increased in regions 1 and 2 during the last five decades. The maximum mean MxDS values appeared in the 2000s for regions 1 and 2 and in the 1990s for region 3. The atmospheric circulation shows that the positive anomaly centre in the west of North China, negative anomaly centre in the east of North China and the strong western Pacific subtropical high led to the decrease of precipitation in North China during the summer of 1997. Copyright © 2013 John Wiley & Sons, Ltd.     

Global ionospheric electron density estimation based on multisource TEC data assimilation

GPS Solutions - We developed a parameterized ionospheric electron density model based on the IRI-2012 model by spherical harmonic expansions in the horizontal and empirical orthogonal functions in...     

柘林水库修河流域降水时空分布特征与旱涝研究

根据1953—1983年降水资料,分析了柘林水库修河流域降水时空分布特征和旱涝规律。降水主要集中在6月中、下旬,有时可推迟到7月中旬,此时暴雨频数高,强度大,历时长,是柘林水库洪水运行管理的关键时期。为此,需要了解梅雨晚期发生的大暴雨的形成条件和时空分布,以及梅雨期旱涝情况和采用预报的风险程度。本文在这方面进行了一些综合性分析,特别是对5,6月旱涝年份的统计规律、环流特征作了较详细的气候学对比研究。     

关于数字水准仪i角指标限差的探讨

通过对数字水准仪在构造和测量原理上与光学水准仪具有不同特点的分析,给出了数字水准仪i角的含义和数字水准仪i角指标限差的量化表述,供仪器使用者和检修人员参考。     

主成分监督分类及其在水质特征遥感图像识别中的应用

建立了一种水域水质状况图像识别的主成分监督分类方法,首先通过ＴＭ水域图像数据的主成分分析,将原有各波段图谱的显著且独立的信息集中在数目尽可能少的合成图象中,再依据不同类型水体的光谱特征,分析各主成分图像的构成及其环境生态学含义,由此对整个研究区域内存在的不同标志类型及其分布特征有所了解,在此基础上,选定训练样本集,从而人有清楚的环境生态意义的标志类型,应用监督法得到较好的识别分类结果,分析表明,这     

SASW法在粉土液化判别中的应用

文章介绍了面波法(SASW法)的基本原理与测试方法,并将该方法用于判别黄河三角洲饱和粉土的液化势.通过标准贯入试验结果与瑞雷波法判别结果的对比,说明以剪切波速为土性指标的液化判别方法是一个很有前景的方法,但由于资料太少,建议继续收集液化调查资料,以发展出一个有充分根据的液化判别方法.     

Deep-seated structure and gold content of Russia and China contiguous territories

On the contiguous territories of southeastern Russia and northeastern China, many gold-bearing areas are conjugate in space with the gradient zones of the gravity field. Large gold-ore districts, defining in many respects the metallogenic signature of the region, are located on the joints of differently oriented gradient zones. In the best-studied districts, the Precambrian protrusions, staged distribution of magmatic chambers ( by vertical) above the Mohorovicic discontinuity and restriction to the peripheral parts of intrusive massifs have been recognized. Different-type gold deposits in the studied ore-placer districts and nodes are often located on the areas of joint of the granitoid massifs and subvolcanic bodieswith depressions. Availability of areals of metasomatic alterations of rocks, placers, and ore occurrences of precious metals on such but poorly studied areas can serve as the basis for the revision and detailed forecasting-prospecting works to develop the mineral-raw material base of the region for precious metals.     

地震作用下多层剪切型组合结构的合理综合阻尼比取值探讨

对于组合结构,提出了一种新的基于单元瑞利阻尼模型的应变能振型阻尼比,并证明了其在特定整体阻尼矩阵下与强迫解耦法的等价性;推导了具有明确理论依据的综合阻尼比计算公式,并基于相应的应变能振型阻尼比得出了结构的刚度综合阻尼比和瑞利综合阻尼比。分别采用复振型分解法和振型分解法对算例结构进行了地震荷载作用下的弹性时程分析,结果表明,瑞利综合阻尼比对于以剪切变形为主的多层组合结构具有良好的计算精度和适用性。     

Effects of initial soil water content and saturated hydraulic conductivity variability on small watershed runoff simulation using LISEM

Abstract

Soil water content (θ) and saturated hydraulic conductivity (K_s) vary in space. The objective of this study was to examine the effects of initial soil water content (θ_i) and K_s variability on runoff simulations using the LImburg Soil Erosion Model (LISEM) in a small watershed in the Chinese Loess Plateau, based on model parameters derived from intensive measurements. The results showed that the total discharge (TD) and peak discharge (PD) were underestimated when the variability of θ_i and K_s was partially considered or completely ignored compared with those when the variability was fully considered. Time to peak (TP) was less affected by the spatial variability compared to TD and PD. Except for TP in some cases, significant differences were found in all hydrological variables (TD, PD and TP) between the cases in which spatial variability of θ_i or K_s was fully considered and those in which spatial variability was partially considered or completely ignored. Furthermore, runoff simulations were affected more strongly by K_s variability than by θ_i variability. The degree of spatial variability influences on runoff simulations was related to the rainfall pattern and θ_i. Greater rainfall depth and instantaneous rainfall intensity corresponded to a smaller influence of the spatial variability. Stronger effects of the θ_i variability on runoff simulation were found in wetter soils, while stronger effects of the K_s variability were found in drier soils. For accurate runoff simulation, the θ_i variability can be completely ignored in cases of a 1-h duration storm with a return period greater than 10 years, while K_s variability should be fully considered even in the case of a 1-h duration storm with a return period of 20 years.

Editor D. Koutsoyiannis; Associate editor A. Fiori     

http://www.sciencedirect.com/science/article/pii/S1674987111001150

The Erlangmiao granite intrusion is located in the eastern part of the East Qinling Orogen.The granite contains almost 99 vol.％ felsic minerals with accessory garnet,muscovite,biotite,zircon,and Fe-Ti ...