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101.
Comparison of SDSM and LARS-WG for simulation and downscaling of extreme precipitation events in a watershed 总被引:12,自引:6,他引:6
Muhammad Zia Hashmi Asaad Y. Shamseldin Bruce W. Melville 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):475-484
Future climate projections of Global Climate Models (GCMs) under different emission scenarios are usually used for developing
climate change mitigation and adaptation strategies. However, the existing GCMs have only limited ability to simulate the
complex and local climate features, such as precipitation. Furthermore, the outputs provided by GCMs are too coarse to be
useful in hydrologic impact assessment models, as these models require information at much finer scales. Therefore, downscaling
of GCM outputs is usually employed to provide fine-resolution information required for impact models. Among the downscaling
techniques based on statistical principles, multiple regression and weather generator are considered to be more popular, as
they are computationally less demanding than the other downscaling techniques. In the present study, the performances of a
multiple regression model (called SDSM) and a weather generator (called LARS-WG) are evaluated in terms of their ability to
simulate the frequency of extreme precipitation events of current climate and downscaling of future extreme events. Areal
average daily precipitation data of the Clutha watershed located in South Island, New Zealand, are used as baseline data in
the analysis. Precipitation frequency analysis is performed by fitting the Generalized Extreme Value (GEV) distribution to
the observed, the SDSM simulated/downscaled, and the LARS-WG simulated/downscaled annual maximum (AM) series. The computations
are performed for five return periods: 10-, 20-, 40-, 50- and 100-year. The present results illustrate that both models have
similar and good ability to simulate the extreme precipitation events and, thus, can be adopted with confidence for climate
change impact studies of this nature. 相似文献
102.
For mineral resource assessment, techniques based on fuzzy logic are attractive because they are capable of incorporating uncertainty associated with measured variables and can also quantify the uncertainty of the estimated grade, tonnage etc. The fuzzy grade estimation model is independent of the distribution of data, avoiding assumptions and constraints made during advanced geostatistical simulation, e.g., the turning bands method. Initially, fuzzy modelling classifies the data using all the component variables in the data set. We adopt a novel approach by taking into account the spatial irregularity of mineralisation patterns using the Gustafson–Kessel classification algorithm. The uncertainty at the point of estimation was derived through antecedent memberships in the input space (i.e., spatial coordinates) and transformed onto the output space (i.e., grades) through consequent membership at the point of estimation. Rather than probabilistic confidence intervals, this uncertainty was expressed in terms of fuzzy memberships, which indicated the occurrence of mixtures of different mineralogical phases at the point of estimation. Data from different sources (other than grades) could also be utilised during estimation. Application of the proposed technique on a real data set gave results that were comparable to those obtained from a turning bands simulation. 相似文献
103.
Mohammad Wasim Mohammad Arif Sajid Iqbal Muhammad Daud 《Geostandards and Geoanalytical Research》2013,37(1):87-93
The International Atomic Energy Agency (IAEA) organised a proficiency test (PT), IAEA‐CU‐2010‐02, for the determination of elements in sewage sludge. The PT sample was analysed by semi‐absolute standardless k0‐instrumental neutron activation analysis (k0‐INAA). Results for seven elements (As, Co, Cr, Fe, Hg, Se, Zn) were submitted to the IAEA by our laboratory. All of our results were scored ‘acceptable’ by the ‘result evaluation criteria’ adopted by the IAEA. The same analytical methodology produced quantitative results for twenty‐six additional elements. In total, thirty‐six elements were determined with uncertainty varying from 4 to 11%. This paper presents the provisional mass fractions of twenty‐six additional elements (Ag, Al, Br, Ca, Ce, Cl, Dy, Eu, Ga, Hf, I, K, La, Mg, Mn, Na, Rb, Sb, Sc, Sm, Ta, Tb, Th, V, U, W) not reported by the IAEA. The analytical methodology was discussed with important sources of spectral, nuclear and fission‐product interferences. It was shown that the important components of uncertainties were the k0 factor, Q0 factor, detector efficiency, mass and counting statistics. The methodology was validated by analysing the IAEA‐S7 reference material. 相似文献
104.
Muhammad Raza Mohamad Pauzi Zakaria Nor Rasidah Hashim Un Hyuk Yim Narayanan Kannan Sung Yong Ha 《Environmental Earth Sciences》2013,70(6):2425-2436
This is a comprehensive study of the composition, origin and sources of specific polycyclic aromatic hydrocarbons (PAHs) in sediments of mangrove estuary in the western part of Peninsular Malaysia. Mangrove sediments were analyzed for 17 PAHs by gas chromatography–mass spectrometry. Total PAH concentrations in the sediments ranged from 20 to 112 ng/g on a dry-weight basis. High molecular weight PAHs were abundant in the sediments. Parent PAH ratios revealed that pyrogenic input has important contribution to the sedimentary PAHs. Ratios of alkylated PAHs indicate that the sedimentary PAHs were influenced by petrogenic PAHs, which implies that petrogenic input has contribution to the sedimentary PAHs but that it is not a major factor in distribution of PAHs within the estuary. Combustion-derived PAHs show a positive and very strong correlation with total PAHs (R 2 = 0.926, p < 0.05). Total methylphenanthrenes show very weak correlation with total PAHs (R 2 = 0.0928, p < 0.05). The PAH concentrations were found to increase with distance from the upstream of the estuary to the coastal area of the Straits of Malacca. For the assessment of sediment contamination using biological thresholds, none of the individual studied PAH compounds exceeded the values of the effect range low–effect range median guideline and the threshold effects level–probable effects level guideline. This study demonstrates that the sediments of the mangrove ecosystem facing the Straits of Malacca and Sumatra are influenced by anthropogenic PAH inputs as a result of human activities such as biomass burning, vehicle emissions and boating activities. 相似文献
105.
Riaz Hossain Khan Muhammad Qumrul Hassan Mohammad Saiful Islam 《Environmental Earth Sciences》2013,69(8):2499-2512
Water quality and hydrochemistry of Shariatpur district were evaluated in terms of hydrochemical composition and some important physico-chemical parameters. The groundwater of the study area is good for drinking, domestic as well as for irrigation purposes. Among the major ions, shallow tube well waters give higher concentration of Ca2+ which ranges from 24 to 260 mg/L. The deep tubewell waters show higher concentration of Na+ which varies from 74 to 582 mg/L during dry season. Among the trace elements most of the shallow aquifer samples show higher concentration of Fe2+, Mn2+ and As. Concentration of Fe2+ varies from 0.655 to 18.8 mg/L, and Mn2+ from trace to 0.868 mg/L during dry period. Hydrochemical analyses reveal significant seasonal variation in water quality of shallow aquifer. Both the shallow aquifer and the surface water of the study area are predominantly of Ca–Mg–HCO3 type, while the deep aquifer water is mainly of Na–K–Cl–SO4 type with slight inclination to Ca–Mg–HCO3 type. The study area is suitable for groundwater development if comprehensive and holistic approaches towards water resource management are taken into consideration. 相似文献
106.
Muhammad Irfan Aziz Akbar Mubashir Aziz Ammad Hassan Khan 《Geotechnical and Geological Engineering》2013,31(2):729-738
Rapid urbanization and expansion of metropolitans in the developing world is pressing the need of tall structures with multiple basements. In several such projects, open land is available around excavation site and unsupported deep excavations by maintaining appropriate side slopes offer economical solution. In this research, subsoil stratigraphy of Lahore district was established to be comprising of a top clay stratum 1.5–8 m thick, followed by a sand layer. Considering subsoil data from several geotechnical investigation reports, the effect of four key parameters viz., cohesion of clay layer, friction angle of sand layer, thickness of clay layer at the top and slope inclination of underlying sand layer on safety factor of open excavations was studied. Six hundred twenty-five slope stability analyses were conducted by considering different geometries and soil properties. Based on the results of these analyses, a regression model was suggested to estimate safety factor of open excavations in similar stratigraphy which would be useful in feasibility studies and preliminary design of deep excavations. It was established that the clay layer cohesion was the most dominant contributor to safety factor. 相似文献
107.
In this work, we consider the framework of non-linear electrodynamics in Bianchi type I universe model composed of matter and electromagnetic field. We deal with electric and magnetic universe separately. In this scenario, we calculate the electric and magnetic fields and their corresponding matter densities using two particular types of interaction terms. We also check the validity of generalized second law of thermodynamics in both universe models enclosed by apparent horizon. It turns out that this law holds on the apparent horizon for a particular range depending upon the parameters. Finally, we discuss the deceleration and statefinder parameters to check the viability of these models. 相似文献
108.
Thermodynamics of a large family of black holes from electrovacuum solutions of Einstein’s equations is studied. This family includes rotating and non-accelerating black holes with NUT charge, and rotating and accelerating black holes. The surface gravity, Hawking temperature and the area laws for these black holes are presented. The first law of thermodynamics is also given. An interesting outcome of our analysis is the restriction obtained on the magnitude of acceleration for these black holes. 相似文献
109.
Garrelt Mellema Léon V. E. Koopmans Filipe A. Abdalla Gianni Bernardi Benedetta Ciardi Soobash Daiboo A. G. de Bruyn Kanan K. Datta Heino Falcke Andrea Ferrara Ilian T. Iliev Fabio Iocco Vibor Jelić Hannes Jensen Ronniy Joseph Panos Labroupoulos Avery Meiksin Andrei Mesinger André R. Offringa V. N. Pandey Jonathan R. Pritchard Mario G. Santos Dominik J. Schwarz Benoit Semelin Harish Vedantham Sarod Yatawatta Saleem Zaroubi 《Experimental Astronomy》2013,36(1-2):235-318
The Square Kilometre Array (SKA) will have a low frequency component (SKA-low) which has as one of its main science goals the study of the redshifted 21 cm line from the earliest phases of star and galaxy formation in the Universe. This 21 cm signal provides a new and unique window both on the time of the formation of the first stars and accreting black holes and the subsequent period of substantial ionization of the intergalactic medium. The signal will teach us fundamental new things about the earliest phases of structure formation, cosmology and even has the potential to lead to the discovery of new physical phenomena. Here we present a white paper with an overview of the science questions that SKA-low can address, how we plan to tackle these questions and what this implies for the basic design of the telescope. 相似文献
110.
Sonja Maultzsch Ramin Nawab Sung Yuh Muhammad Idrees Bernard Frignet 《Geophysical Prospecting》2009,57(2):263-274
We present the analysis of a multi-azimuth vertical seismic profiling data set that has been acquired in a tight gas field with the objective of characterizing fracture distributions using seismic anisotropy. We investigate different measurements of anisotropy, which are shear-wave splitting, P-wave traveltime anisotropy and azimuthal amplitude variation with offset. We find that for our field case shear-wave splitting is the most robust measure of azimuthal anisotropy, which is clearly observed over two distinct intervals in the target. We compare the results of the vertical seismic profiling analysis with other borehole data from the same well. Cross-dipole sonic and Formation MicroImager data from the reservoir section suggest that no open fractures intersect the well or are present within half a metre of the borehole wall. Furthermore, a detailed dispersion analysis of the sonic scanner data provides no indication of stress-induced seismic anisotropy along the logged borehole section. We therefore explain the azimuthal anisotropy measured in the vertical seismic profiling data with a model that contains discrete fracture corridors, which do not intersect the well itself but lie within the vertical seismic profiling investigation radius. We show that such a model can reproduce some basic characteristics of azimuthal anisotropy observed in the vertical seismic profiling data. The model is also consistent with well test data that suggest the presence of a fracture corridor away from the well. With this study we demonstrate the necessity of integrating different data types that investigate different scales of rock volume and can provide complementary information for understanding the characteristics of fracture networks in the subsurface. 相似文献