Fitting optimum order of Markov chain models for daily rainfall occurrences in Peninsular Malaysia     

Sayang Mohd Deni  Abdul Aziz Jemain  Kamarulzaman Ibrahim 《Theoretical and Applied Climatology》2009,97(1-2):109-121

The analysis of the daily rainfall occurrence behavior is becoming more important, particularly in water-related sectors. Many studies have identified a more comprehensive pattern of the daily rainfall behavior based on the Markov chain models. One of the aims in fitting the Markov chain models of various orders to the daily rainfall occurrence is to determine the optimum order. In this study, the optimum order of the Markov chain models for a 5-day sequence will be examined in each of the 18 rainfall stations in Peninsular Malaysia, which have been selected based on the availability of the data, using the Akaike’s (AIC) and Bayesian information criteria (BIC). The identification of the most appropriate order in describing the distribution of the wet (dry) spells for each of the rainfall stations is obtained using the Kolmogorov-Smirnov goodness-of-fit test. It is found that the optimum order varies according to the levels of threshold used (e.g., either 0.1 or 10.0 mm), the locations of the region and the types of monsoon seasons. At most stations, the Markov chain models of a higher order are found to be optimum for rainfall occurrence during the northeast monsoon season for both levels of threshold. However, it is generally found that regardless of the monsoon seasons, the first-order model is optimum for the northwestern and eastern regions of the peninsula when the level of thresholds of 10.0 mm is considered. The analysis indicates that the first order of the Markov chain model is found to be most appropriate for describing the distribution of wet spells, whereas the higher-order models are found to be adequate for the dry spells in most of the rainfall stations for both threshold levels and monsoon seasons.  相似文献   

The best fitting distribution of annual maximum rainfall in Peninsular Malaysia based on methods of L-moment and LQ-moment   总被引：1，自引：1，他引：0  

Wan Zawiah Wan Zin  Abdul Aziz Jemain  Kamarulzaman Ibrahim 《Theoretical and Applied Climatology》2009,98(3-4):337-350

This paper discusses patterns of annual and monthly precipitation variability at seven weather stations in east central Europe (1851–2007). Precipitation patterns were compared to three simple regional indices of atmospheric circulation, i.e., western circulation, southern circulation and the cyclonicity (C) index and a relationship between precipitation and the North Atlantic Oscillation index was identified. Correlations of the monthly records and multiple regression, using a principal components’ analysis, helped determine the statistical significance of the dependence of precipitation on the circulation indices. The Mann–Kendall test revealed no trend to change in any of the precipitation series, but a certain spatial regularity could be discerned in the phase of the annual periodic component. A common feature of the variability in central European annual precipitation is the dry period identified in the 1980s and the first half of the 1990s. In the northern part of the region, above-average precipitation was noted from the 1960s through to the mid-1970s as a result of the frequent prevalence of depressions. South of the divide, the wettest period was recorded at the turn of 1930s/1940s. After a number of very wet years in the last decade of the twentieth century and the beginning of the twenty-first century, precipitation began to fall at all of the region’s weather stations. The C index is the strongest circulation-linked factor influencing precipitation in central Europe and it accounts for more than 40% of the variance in spatially averaged wintertime precipitation.  相似文献   

Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya,India     

Abdul Matin  Sweety Mazumdar 《Journal of Earth System Science》2009,118(4):379-390

Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso- to micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse.  相似文献   

Astrophysical parameters of ten poorly studied open star clusters     

Ashraf Latif Tadross  Reda El-Bendary  Anas Osman  Nader Ismail  Abdel Aziz Bakry 《天体物理学报》2012,(1):75-83

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Cosmic energy equation for extended structures and its application to gravitational galaxy clustering     

Abdul Wahid  Ajaz Ahmad 《Astrophysics and Space Science》2012,341(2):611-616

Cosmic energy equation represents the law of conservation of energy in the region expanding with time as the universe expands. It gives the evolution of kinetic and correlation potential energy with time in a cluster expanding as the universe expands. To understand the clustering of galaxies under the influence of gravitational force, cosmic energy equation is of great help. We use cosmic energy equation for extended structures (galaxies with halos) to analyse the gravitational galaxy clustering in different ways. We try to understand the influence of expansion on the clustering by deriving the relation between correlation parameter b _V and scale factor R. We also derive the relation between the peculiar kinetic energy K and correlation parameter to know that when peculiar kinetic energy dominates over the kinetic energy of galaxies due to expansion. Besides, the evolution of specific heat and energy provides the information regarding the different states of clustering.  相似文献   

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir,Borneo:Implications for reservoir characterization and flow simulation     

Numair A.Siddiqui  Mu.Ramkumar  Abdul Hadi A.Rahman  Manoj J.Mathew  M.Santosh  Chow W.Sum  David Menier 《地学前缘(英文版)》2019,10(3):957-971

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2 D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo.Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics.These proportions were then enumerated in terms of static digital outcrop model(DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone(porosity 21.25%-41.2%and permeability 1265.20-5986.25 mD) and moderate quality sandstone(porosity 10.44%-28.75% and permeability 21.44-1023.33 mD). Whereas, in more heterolithic sandstone(wavy-to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone(porosity 3.4%-12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.  相似文献   

Generation of a stochastic precipitation model for the tropical climate     

Ng  Jing Lin  Abd Aziz  Samsuzana  Huang  Yuk Feng  Wayayok  Aimrun  Rowshon  MK 《Theoretical and Applied Climatology》2018,133(1-2):489-509

Theoretical and Applied Climatology - A tropical country like Malaysia is characterized by intense localized precipitation with temperatures remaining relatively constant throughout the year. A...  相似文献   

The effectiveness of the very low frequency electromagnetic method (VLF-EM) in the exploration of sulphide mineralization in arid environments,case study from South Sinai Peninsula,Egypt     

El-Arabi Shendi  Akram Aziz  Khalid Mamoun  Mohamed Gamal 《Environmental Earth Sciences》2017,76(22):783

Very low frequency electromagnetic (VLF-EM) measurements were carried out in Wadi Isbayia area, south Sinai Peninsula, to test the efficiency of the VLF-EM method in the exploration of sulphide mineralization in arid environments. The VLF-EM field measurements, including tilt angle, real and imaginary components of the received VLF field, were carried out along fifteen profiles covering a quartz monzonite bedrock. Interpretation of the VLF measurements, in the light of geological information, has showed that sulphide minerals in the Wadi Isbayia area extend from the ground surface to a depth of about 200 m. However, the structural lineaments, especially faults, have controlled the distribution of the sulphide mineralization. A few of polished sections for rock samples, collected from the sites of the VLF-EM anomalies in the study area, have been prepared and examined by ore microscopy which confirmed the presence of pyrite and chalcopyrite as well as iron oxides, disseminated in the quartz monzonite bedrock. These results showed that the VLF-EM method is an effective tool in the exploration of sulphide minerals in the arid environments.  相似文献   

Multi-criteria decision-making analysis in selecting suitable plotting positions for IDF curves of storm events     

Noratiqah Mohd Ariff  Abdul Aziz Jemain  Mohd Aftar Abu Bakar 《Environmental Earth Sciences》2017,76(17):625

Selecting suitable distributions for rainfall data is usually subjective and complex since it requires decision-makers to consider results from various measures of goodness-of-fit indices. In this study, the VIKOR method in multi-criteria decision-making analysis is modified to select the most suitable plotting positions to represent extreme storm intensities in order to build the intensity–duration–frequency (IDF) curves of storm events. This is done by considering the rankings provided by all goodness-of-fit indices used to obtain a compromise solution. Nine plotting positions are considered: Weibull (W), Adamowski (A), Gringorten (G), Hazen (H) and Gumbel (EV I) and two known plotting positions for generalized extreme value (GEV) distribution using Pearson’s skewness and another two using L-skewness. The IDF curves obtained are compared to a reference IDF curves which was found using the GEV distribution. The mean and median for three goodness-of-fit indices, the coefficient of variation of root mean square error, CV_RMSE, the mean percentage of difference, Δ, and the coefficient of determination, R ², are taken as the criteria for selection process. The results show that six plotting positions, A, H, W, G and the two plotting positions with L-skewness, are equally superior compared to the other three plotting positions.  相似文献   

Morphotectonic controls of groundwater flow regime and relating environmental impacts in Northwest Sinai,Egypt     

Ahmed E. El-Rayes  Mohamed O. Arnous  Akram M. Aziz 《Arabian Journal of Geosciences》2017,10(18):401

The frequent appearance of some hydro-environmental hazard features, such as waterlogging and soil salinization along the susceptible zones at Northwest Sinai area (NWSA), has put serious challenges and obstacles for a correct and efficient land use planning of this region, for several decades. Although previous studies have shown that the whole region of Northern Sinai is greatly affected by the tectonic movements associated with the Syrian Arc folding system (SAS), NWSA is barren of any obvious surficial structures. The current work aims to investigate the effect of subsurface tectonic features on the hydrogeologic regime of NWSA.Hydrogeological and remote sensing data were integrated with ground geophysical gravity and magnetic measurements, using the geographic information system. Data integration asserts the role played by buried tectonic features not only in governing the landforms of the upper water-bearing quaternary formations but also in controlling their flow regime.Two major subsurface structures were identified through interpreting the geophysical measurements. A buried dome-like structure, dominating the central part of the mapped area, coincides with the radial flow pattern observed on the water table map. At the southwestern corner of the study area, an elevated groundwater level, caused by continuous groundwater accumulation at the discharge boundary, is superimposing a subsurface block-faulted depression. The waterlogging features (saturation of the soil by groundwater and inundation of local depressions due to rising of water table) dominating the discharge lowlands of NWSA support the conclusion that a buried block-faulted structure exerts a strong influence on the thickness and groundwater flow regime of the shallow quaternary aquifer.  相似文献