Uncertainty assessment in river flow projections for Ethiopia’s Upper Awash Basin using multiple GCMs and hydrological models

ABSTRACT

Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios for the period 2071–2100. Hydrological models vary in their spatial distribution and process representations of unsaturated and saturated zones. Very good performance is achieved for 1975–1999 (NSE: 0.65–0.8; r: 0.79–0.93). GCM-related uncertainty dominates variability in projections of high and mean discharges (mean: –34% to +55% for RCP4.5, – 2% to +195% for RCP8.5). Although GCMs dominate uncertainty in projected low flows, inter-hydrological model uncertainty is considerable (RCP4.5: –60% to +228%, RCP8.5: –86% to +337%). Analysis of variance uncertainty attribution reveals that GCM-related uncertainty occupies, on average, 68% of total uncertainty for median and high flows and hydrological models no more than 1%. For low flows, hydrological model uncertainty occupies, on average, 18% of total uncertainty; GCM-related uncertainty remains substantial (average: 28%).     

Aragonite crystallization from strained calcite at reduced pressures and its bearing on aragonite in low-grade metamorphism

Aragonite, the dense form of CaCO₃, grew hydrothermally at 100–300° C and dry at 300–400° C at very low pressures from calcite strained by grinding. Nearly complete inversion to aragonite occurred in some runs with Ca-Mg chloride solutions at 0–2.4 kb and 100–200° C on strained calcite having a (10¯14) reflection with a half-width of 0.48° 2 Cu K. A little aragonite grew dry at one atm. from the ground calcite at 300–400° C in a few hrs. Simultaneous shear during recrystallization of calcite in a rotating squeezer resulted in significant aragonite at 300–400° C several kb. below the stability field. No inversion occurred in any ground calcite when previously annealed in CO₂ at 500° C for a few hrs. Thermochemical data show that at least 200 cal/mole of strain energy can be produced in calcite by mild deformation. This much stored energy would lower the pressure requirements of aragonite, relative to the strained calcite by more than 3 kb, and our observation that aragonite growth was faster than strain recovery of calcite indicates that aragonite can grow in nature at reduced pressures from strained calcite.Some experiments were also carried out on highly magnesian calcites with the thought that aragonite might also form at the expense of this metastable material. No aragonite was produced, but the possibility that this mechanism could be operative in nature cannot be discounted.The microtexture of aragonitic deformed marbles from NW Washington (prehnite-pumpellyite facies rocks, courtesy of J. A. Vance) as well as electron probe microanalysis of these rocks indicates that aragonite selectively replaced highly strained calcite. The calcite-aragonite transition is thus a questionable indicator of high-pressure in certain metamorphic rocks.     

小波变换及其在影像表示中的应用和其方向选择性算法的改进

小波理论是研究多分辨率信号处理的理论,目前被公认为有前途的新理论。金字塔结构的影像处理、影像理解,现代GIS处理多比例尺的要求以及地形、场论中的逼近均需有关这一理论的支持。本文利用小波变换分解原始影像以实现影像的小波表示,并发展为任意方向的小波变换、逆变换,利用它检测航片中建筑物及其阴影的公共边缘。这种表示方式可为某些影像特征或识别目标提供较为经济的分辨率,该表示方式使影像中具有一定层次的结构更易于发现和利用。实验结果证明了此方法是有效的。     

Self-Affine Fractals and the Fractal Dimension of Fractured Rock Profiles

The measured profiles of laboratory fractured rocks should be self-affine fractal.The scaling properties of these profiles are described by two parameters-the fractal dimension D and the crossover length tc The D values of eight profiles are calculated by the ruler method and by the standard deviation method respectively.It is shown that if tc is far greater than the sampling step tc two methods yield the same results,although if it is far smaller than r,the D by the standard method will be about 1.20,while D by the ruler method will very close to 1.0,because two fractal dimensions,local and global,exist on two sides of tc In order to obtain the local fractal dimension which may be close to that of the standard deviation method,the ruler method must be modified.We propose a way to estimate the tc and to modify the ruler method.Finally,a profile having given D is generated in terms of the principle of non-integer order differential,through which the above two methods are verified and lead to the same res     

陕西灞源地区金矿远景区统计预测

近年来经初步工作在陕西灞源地区查明、发现小型金矿床、矿点共31处，本文根据矿点本身的各种特征，用模糊综合评判法对矿点矿化强度进行了评价和排序，以此为基础建立单元含矿性变列，筛选出成矿环境变量16个，用逻辑信息法在区内圈出金矿远景区A类40km^-2，B类46km^-2.为本区金矿进一步勘查工作部署提供了依据。     

Ce-anomalous lavas from Rabaul caldera,Papua New Guinea

REE abundances for a suite of Rabaul caldera lavas ranging from basalt to dacite are reported. Three of the lavas contain negative Ce anomalies. These ‘anomalous’ lavas are older and have a geochemistry different from the younger lavas which form the main Rabaul caldera. The consistent geochemical differences between the two groups of lavas suggest that the Ce anomaly is inherited from the source material from which the magmas were derived and is not due to differences in crystallization or fractionation paths. Ocean floor lavas containing zeolite assemblages have been shown to possess a Ce anomaly and it is concluded that those lavas having a Ce anomaly were derived from lithosphere which had been depleted in Ce during weathering and hydrothermal processes.     

Undersaturated lavas from Ambittle Island,Papua New Guinea

Ambittle is part of a gently arcuate chain of Quaternary volcanic islands east of the Bismarck Archipelago. Lavas include basanities, tephrites, ankaramitic lavas and trachyte. Phenocrysts of olivine, clinopyroxene and plagioclase are found in bauonite along with hauyne. Olivine and less commonly hauyne are absent from tephrite while amphibole and biotite are common. Nodules in the lavas are composed of phenocryst phases and are thought to represent crystal clots or cumulates. Low Ti, high Al, low Ni and Cr and high Sr, Rb mark these lavas as being very different from basanites of intra-continental regions. Suggested parallels are shoshonitic lavas from the Aeolian Islands and feldspathoidal lavas from Indonesia. Although the structure in the region of Ambittle is not well known it seems likely that the magmas were linked to tectonic processes along a subducting plate margin. The presence of basalts of transitional affinity in other islands of the chain suggests a petrochemical link with the undersaturated types. Derivation of undersaturated lavas form partial melts formed in the mantle only seems possible if ol + cpx are fractionated at moderate pressures in order to enrich residual liquids in Al. If the undersaturated lavas are related to a parental transitional tholeiite magma then fractionation processes alone are insufficient to explain their composition and processes of volatile differentiation may have occurred.     

A Probabilistic Displacement-based Vulnerability Assessment Procedure for Earthquake Loss Estimation

Earthquake loss estimation studies require predictions to be made of the proportion of a building class falling within discrete damage bands from a specified earthquake demand. These predictions should be made using methods that incorporate both computational efficiency and accuracy such that studies on regional or national levels can be effectively carried out, even when the triggering of multiple earthquake scenarios, as opposed to the use of probabilistic hazard maps and uniform hazard spectra, is employed to realistically assess seismic demand and its consequences on the built environment. Earthquake actions should be represented by a parameter that shows good correlation to damage and that accounts for the relationship between the frequency content of the ground motion and the fundamental period of the building; hence recent proposals to use displacement response spectra. A rational method is proposed herein that defines the capacity of a building class by relating its deformation potential to its fundamental period of vibration at different limit states and comparing this with a displacement response spectrum. The uncertainty in the geometrical, material and limit state properties of a building class is considered and the first-order reliability method, FORM, is used to produce an approximate joint probability density function (JPDF) of displacement capacity and period. The JPDF of capacity may be used in conjunction with the lognormal cumulative distribution function of demand in the classical reliability formula to calculate the probability of failing a given limit state. Vulnerability curves may be produced which, although not directly used in the methodology, serve to illustrate the conceptual soundness of the method and make comparisons with other methods.