Synoptic and remote sensing analysis of dust events in southwestern Iran

Southwest regions of Iran, due to dry environmental and climatic conditions, have been identified as one of the five major regions in the world. In recent years, large parts of Iran have been affected by suspended particles from the dust storms. The studied area is located in foothills of the Zagros Mountain Range just north of Persian Gulf in southwest of Iran. Dust and other meteorological data were prepared in 3-hour intervals from 12 synoptic weather stations. For tracking dust storms, satellite images of MODIS were used. Atmospheric conditions during the occurrence of dust storms were determined using NCEP reanalysis data. According to the statistical calculations, most storms occurred in the spring and summer. The lowest number of dust events occurred in the fall and winter particularly in December and January, when there are high possibilities of rainfall occurrence and dynamical instability conditions in the north and west of the region. The results illustrated that the highest amounts of hourly dust occurred in the afternoon and the lowest amounts occurred at 00UTC (3.30 am local times). It seems that it is closely related to the heating surface and the occurrence of local dry instabilities. Analyses of data showed that dust amounts (or volumes) in all the stations have two climactic peaks, first between 1982 and 1990 and second between 2005 and 2008 periods. These peaks can be related to a variety of factors including anthropogenic factors such as war, agricultural activities, dam construction, and widespread droughts.     

Probabilistic Analysis of Ground Surface Vibration Due to Train Movement, a Case Study on Tehran Metro Line 4

Ground surface vibration produced by moving train is one of the most important aspects in urban areas. The purpose of this study is the probabilistic analysis of ground surface vibration, which is generated by metro transportations. For this reason, Tehran metro line 4 is considered as a case study. In this paper, at first, a new procedure is used to simulate train dynamic load. In the second step, based on the variation of geomechanical properties and train characteristics in Tehran metro line 4, more than 60 numerical models are simulated. The results of numerical simulations are analyzed by multivariate statistical technique and an equation for prediction of peak particle velocity (PPV) in the ground surface is presented. In the next step, probabilistic analysis is done using Monte Carlo Simulation (MCS). Finally, sensitivity of input data on ground surface vibration is discussed and the impact of geomechanical properties and train characteristics on the surface vibration is considered. Based on the probabilistic analysis, PPV in the surface region of Tehran metro line 4 is <2.76?mm/s with 95?% probability.     

On the criteria for the initiation of motion in tidal inlets,deterministic and stochastic approaches

Details are given herein of the refinement and application of a three-dimensional layer integrated numerical model to predict morphological changes in tidal basins. The solution of governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for the suspended sediment fluxes and the sediment mass conservation equation for the bed level changes are carried out by the use of Alternating Direction Implicit (ADI) Finite Difference Method (FDM). The model includes different criteria for the initiation of motion namely Shields (1936, Application of Similarity Principles and Turbulence Research to Bed load Movement, Hydrodynamics Laboratory, California Institute of Technology, Pub. No. 167), Kolahdoozan (1999, Numerical Modelling of Geomorphological Processes in Estuarine Waters, PhD Thesis, Department of Civil and Environmental Engineering, University of Bradford, Bradford, UK, 288) and Zanke (2003, On the Influence of Turbulence on the Initiation of Sediment Motion, International Journal of Sediment Research, 18(1), 17–31), to compare different aspects of flow conditions. As the flow is highly turbulent with the random nature of its components, many researchers have tried to express sediment transport processes by using stochastic approaches. In the current study both deterministic and stochastic methods are included in the numerical model to evaluate their accuracy and efficiency. To validate the numerical model results, laboratory measurements are used, with these being obtained from an earlier experimental program undertaken by the authors. Results of a short term bed level changes in a laboratory model harbor are included for the model verification purposes. Comparisons are undertaken using different criteria for the initiation of motion, with the results highlighting that the unsteadiness in the flow parameters included in the numerical model has a major effect on the bed level changes inside the harbor, in compare with the turbulence structure of the flow. The model is then applied to a real case study of the Humber Estuary, located in the UK, with comparisons being undertaken for different criteria for the initiation of motion, using both deterministic and stochastic approaches for the long term bed level predictions.     

Axisymmetric transient waves in transversely isotropic half-space

A transversely isotropic material in the sense of Green is considered. Using a series of potential functions proposed in [Eskandari-Ghadi M. A complete solution of the wave equations for transversely isotropic media. J Elasticity 2005; 81:1–19], the solutions of the transient wave equations within a half-space under surface load are obtained in the Laplace–Hankel domain for axisymmetric problems. The solutions are investigated in detail in the special case of a surface point force pulse varying with time as Heaviside function. Using Cagniard–De Hoop method, the inverse Laplace transform and inverse Hankel transform of the solutions are then obtained in the form of integrals with finite limits. For validity of the analytical results, the final formulations for surface waves are degenerated for an isotropic material and compared with the existing formulation obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80], to show that they are exactly the same. The numerical evaluations of the integrals for some transversely isotropic materials as well as an isotropic one are obtained. The present approach is then numerically verified by comparing a particular case of displacements for the surface of an isotropic half-space subjected to a point load of Heaviside function with the solutions obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80]. In addition, the wave equations for the mentioned medium are obtained on the vertical line directly under the applied surface load. The final formulations are degenerated for an isotropic material and compared with the existing formulation given in Graff [Wave motion in elastic solids. New York: Dover Publications Inc; 1975 [New Ed edition, November 1991]], to show that they are also exactly the same. Then equations are presented in graphical forms using an appropriate numerical evaluation.     

Risk assessment of agricultural water requirement based on a multi-model ensemble framework,southwest of Iran

Water shortage and climate change are the most important issues of sustainable agricultural and water resources development. Given the importance of water availability in crop production, the present study focused on risk assessment of climate change impact on agricultural water requirement in southwest of Iran, under two emission scenarios (A2 and B1) for the future period (2025–2054). A multi-model ensemble framework based on mean observed temperature-precipitation (MOTP) method and a combined probabilistic approach Long Ashton Research Station-Weather Generator (LARS-WG) and change factor (CF) have been used for downscaling to manage the uncertainty of outputs of 14 general circulation models (GCMs). The results showed an increasing temperature in all months and irregular changes of precipitation (either increasing or decreasing) in the future period. In addition, the results of the calculated annual net water requirement for all crops affected by climate change indicated an increase between 4 and 10 %. Furthermore, an increasing process is also expected regarding to the required water demand volume. The most and the least expected increase in the water demand volume is about 13 and 5 % for A2 and B1 scenarios, respectively. Considering the results and the limited water resources in the study area, it is crucial to provide water resources planning in order to reduce the negative effects of climate change. Therefore, the adaptation scenarios with the climate change related to crop pattern and water consumption should be taken into account.

     

The climate change effect on probable maximum precipitation in a catchment. A case study of the Karun river catchment in the Shalu bridge site (Iran)

Probable maximum precipitation (PMP) is assessed on the example of the Karun catchment (the Shalu bridge area). The climate change effects on PMP are investigated under three scenarios: A1B, A2, and B1. It is established that the PMP value for 24, 48, and 72 hours is 127, 170, and 185 mm, respectively. It is demonstrated that the PMP value will decrease by up to 5% under A1B scenario, and will increase by up to 5% and 10% under A2 and B1 scenarios, respectively.     

Forced vertical and horizontal movements of a rectangular rigid foundation on a transversely isotropic half‐space

An analytical investigation of a half‐space containing transversely isotropic material under forced vertical and horizontal displacements applied on a rectangular rigid foundation is presented in this paper. With the goal of a rigorous solution to the shape‐ and rigidity‐ induced singular mixed boundary value problem, the formulation employs scalar potential representation, the Fourier expansion and the Hankel integral transforms method to obtain the surface arbitrary point‐load solution in cylindrical coordinate system. The obtained Green's functions are rewritten in rectangular coordinate system, allowing the response of the half‐space because of an arbitrary distributed load on a rectangular surface area be given in terms of a double integral. The numerical evaluations of stresses are done with the use of an element, which is singular at the edge and the corner of the rectangle. Upon the imposition of the rigidity displacement boundary condition for a rigid foundation and the use of a set of two‐dimensional adaptive‐gradient elements, which can capture the singular behavior in the contact stress effectively, a set of new numerical results are presented to illustrate the effect of transverse isotropy on the foundation response. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydroclimatic variations over the last two glacial/interglacial cycles at Lake Urmia,Iran

A coarse-resolution, absolutely dated isotope record spanning the last 180 ka was constructed from aragonite-rich fecal pellets in a sediment core from Lake Urmia, Iran. The isotope record is not continuous as a consequence of detrital calcite that contaminates the pellets at certain depths. An isotopic correction was applied to samples > 50% aragonite, using the δ¹⁸O values of calcite-only pellets. Absolute dates were derived from U-Th analyses on pellets > 80% aragonite. The resultant δ¹⁸O record and sediment lithofacies confirm that the Penultimate Glacial was cold and dry, with pronounced interstadials at ca. 150 and >175 ka. Deglaciation began at ca. 130 ka, but climate was unstable and supported a probable no-analog vegetation assemblage. The onset of true interglacial conditions occurred at ca. 126 ka. Peak moisture conditions lasted for 5–6 ka before the climate became drier, with the loss of some tree taxa towards the end of the Last Interglacial. A period of greater moisture occurred between 116 and 108 ka, overlapping in timing with interstadial conditions recorded in the Soreq Cave speleothem record. In general, stadial to interstadial transitions (OIS 5d-5c, 5b-5a) are marked by decreasing δ¹⁸O values and rising lake levels. The nature of the OIS 5 to OIS 4 transition cannot be resolved in this study because of the loss of 5 m of core and imprecise dates. According to the present chronology, δ¹⁸O values, and inferred lake levels, arid conditions began at 60 ka and persisted until Termination I. Episodic increases in moisture, characterized by layers of aragonite-rich pellets, ostracodes, and the pollen of trees and/or aquatic plants, occurred during the Last Glacial. Deglaciation associated with the Late-glacial Interstadial began at 14 ka but was interrupted by a marked Younger Dryas event that resulted in renewed aridity. The Holocene began at approximately 10 ka. Despite large errors in the chronology, the overall timing and pattern of effective moisture matches the record from Soreq Cave, Israel, suggesting that the two regions were climatically in-phase.     

Age, growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in the Gomishan wetland – southeast Caspian Sea

A total of 2256 specimens of Atherina boyeri caught in Gomishan wetland (a marsh lagoon located at the southeast Caspian Sea) during spawning season from February to August 2007 were examined for life-history attributes. The population has a 4-year life cycle. Length–weight relationship was estimated as W = 0.0053TL^3.0181 for males and W = 0.0050TL^3.063 for females, being allometrically positive for both sexes. The von Bertalanffy growth function fitted to back-calculated size at age data was: Lt = 155.17[1 − exp − 0.28(t + 0.738)] and Lt = 162.77[1 − exp − 0.27(t + 0.727)] for males and females respectively. The sex ratio was 1:1.30 in favor of females. The reproductive season, evaluated from GSI, extended from March to July, with a peak in March. The average absolute and relative fecundities were 2976 eggs and 874 eggs g⁻¹ of body weight respectively. The diameter of oocytes ranged from 0.03 to 0.20 mm with a mean value of 0.68. The life-history patterns of A. boyeri in the population under study imply that the population of this species in the southeast Caspian Sea differs markedly from those of other localities of its range distribution. The differences were thought to be due to differences in geographical locations.     

Leaching of an oxide gold ore with chloride/hypochlorite solutions

An oxide gold ore was subjected to chloride/hypochlorite leaching at room temperature. The effects of three factors, including Ca(OCl)₂ vs. NaOCl, OCl⁻ concentration, and HCl concentration on gold leaching performance were investigated. Due to formation of CaOCl⁺ complex in solution and hence less reactivity, calcium hypochlorite produces a sluggish gold leaching kinetics, taking twice the time (46 h) to achieve maximum gold recovery of 58% compared to sodium hypochlorite. 10 g/L of total initial hypochlorite species in solution produces reasonable gold recoveries. The amount of added HCl and hence the initial pH was found to have a major effect on gold leaching kinetics and maximum gold recovery. A high level of 9 g/L of added HCl causes HClO to be very reactive, producing very fast kinetics, reaching 67% gold extraction in 4 h. It also causes a faster consumption of hypochlorous acid, through catalytic decomposition (by NiO and CuO) and disproportionation. Hypochlorous acid reactions with sulfide and ferrous content of ore proceed very slowly in the pH range of 4–11. Gold–chloro complexes are strongly adsorbed on quartz component of ore. To minimize this undesirable adsorption of gold–chloro species, the aging time must be limited to a few hours only.