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Assessment of climate variations in temperature and precipitation extreme events over Iran 总被引：1，自引：0，他引：1
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Summary The boundary-layer wind field during weak synoptic conditions is largely controlled by the nature of the landscape. Mesoscale
(sub-synoptic) circulations result from horizontal gradients of sensible heat flux due to variation in local topography, variation
in surface-cover, and discontinuities such as land-sea contrasts. Such flows are usually referred to as thermally-driven circulations,
and are diurnal in nature and often predictable. In this paper we use a state-of-the-art non-hydrostatic computer model to
shed light on the physical mechanisms that drive a persistent easterly wind that develops in the afternoon in the Mackenzie
Basin, New Zealand. The easterly – Canterbury Plains Breeze (CPB) – is observed early in the afternoon and is often intense,
with mean wind speeds reaching up to 12 m s−1. Although computer modelling in mountainous terrain is extremely challenging, the model is able to simulate this circulation
satisfactorily. To further investigate the mechanisms that generate the Canterbury Plains Breeze, two additional idealized
model experiments are performed. With each experiment, the effects of the synoptic scale wind and the ocean around the South
Island, New Zealand were successively removed. The results show that contrary to previous suggestions, the Canterbury Plains
Breeze is not an intrusion of the coastal sea breeze or the Canterbury north-easterly, but can be generated by heating of
the basin alone. This conclusion highlights the importance of mountain basins and saddles in controlling near-surface wind
regimes in complex terrain. 相似文献
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Baroclinic terms have been implemented in a three-dimensional fully hydrodynamic model developed by Badiei et al. [2008. A three-dimensional non-hydrostatic boundary fitted model for free surface flows. International Journal for Numerical Methods in Fluids, 56(6), 607-627] modifying its momentum equations to account for density gradients and utilizing the scalar (salinity, temperature, etc.) conservation equation (SCE) and a state equation for the calculation of density. In the solution of advection-diffusion terms of the governing Navier-Stokes equations (NSE) and SCE, a symmetric splitting method was applied to ensure the long-term stability of simulations. Correction terms proposed by Ruddic et al. (1995) were applied to SCE to ensure the conservation of the scalar quantity. In the presence of baroclinic terms, the zero gradient pressure in the vertical direction in the vicinity of surface and bottom boundaries assumed by Badiei et al. [2008. A three-dimensional non-hydrostatic boundary fitted model for free surface flows. International Journal for Numerical Methods in Fluids, 56(6), 607-627] created spurious currents. This problem was solved by assuming a hydrostatic pressure variation at those boundaries. The ability of extended model was validated by comparing its results with an experimental test case. The simulation of hydrodynamic and salt intrusion at Anzali Port located at the southern coasts of Caspian Sea in Iran was carried out by the model with both barotropic and baroclinic modes. The simulated results with baroclinic mode show a better agreement with measured data as compared to the results of barotropic mode that clearly demonstrate the significance of baroclinic terms in the simulation of cyclic intrusion of salt wedge into the Port Basin. 相似文献
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Shahab Shahbeik Peyman Afzal Parviz Moarefvand Mania Qumarsy 《Arabian Journal of Geosciences》2014,7(9):3693-3704
Estimation of mineral resources and reserves with low values of error is essential in mineral exploration. The aim of this study is to compare inverse distance weighted (IDW) and ordinary kriging (OK) methods based on error estimation in the Dardevey iron ore deposit, NE Iran. Anisotropic ellipsoid and variograms were calculated and generated for estimation of Fe distribution by both methods. Density, continuity of ore and waste, the number of points involved, and the discretization factor in the estimation of ore and waste boundaries were determined and the resource estimated by IDW and OK methods. Estimation errors were classified based on JORC standard, and both methods were compared due to distribution of error estimation. Results obtained by the study indicate that error estimation of OK method is less than IDW method and that the results of OK method are reliable. 相似文献
6.
Masoumeh NABILOU Peyman AFZAL Mehran ARIAN Ahmad ADIB Hassan KHEYROLLAHI Mohammad FOUDAZI Parviz ANSARIRAD 《《地质学报》英文版》2022,96(2):591-606
Multifractal modeling is a mathematical method for the separation of a high potential mineralized background from a non-mineralized background. The Concentration-Distance to Fault structures (C-DF) fractal model and the distribution of the known iron (Fe) deposits/mines seen in the Esfordi and Behabad 1:100,000 sheets from the Bafq region of central Iran are used to distinguish Fe mineralization based on their distance to magnetic basement structures and surface faults, separately, using airborne geophysical data and field surveys. Application of the C-DF fractal model for the classification of Fe mineralizations in the Esfordi and Behabad areas reveals that the main ones show a correlation with their distance from magnetic basement structures. Accordingly, the distances of Fe mineralizations with grades of Fe higher than 55% )43% < Fe ≤ 60%) are located at a distance of less than 1 km, whereas for surfacial faults with grades of 43% ≤ Fe ≤ 60%, the distances are 3162< DF ≤ 4365 m from the faults. Thus, there is a positive relationship between Fe mineralization and magnetic basement structures. Also, the proximity evidence of Precambrian high-grade Fe mineralization related to magnetic basement structures indicates syn-rifting tectonic events. Finally, this C-DF fractal model can be used for exploration of magmatic and hydrothermal ore deposits. 相似文献
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Marwan?KaturjiEmail author Andrew?Sturman Peyman?Zawar-Reza 《Boundary-Layer Meteorology》2011,139(1):143-160
An investigation into high Reynolds number turbulent flow over a ridge top in New Zealand is described based on high-resolution
in-situ measurements, using ultrasonic anemometers for two separate locations on the same ridge with differing upwind terrain
complexity. Twelve 5-h periods during neutrally stratified and weakly stable atmospheric conditions with strong wind speeds
were sampled at 20 Hz. Large (and small) turbulent length scales were recorded for both vertical and longitudinal velocity
components in the range of 7–23 m (0.7–3.3 m) for the vertical direction and 628–1111 m (10.5–14.5 m) for the longitudinal
direction. Large-scale eddy sizes scaled to the WRF (Weather Research and Forecasting) numerical model simulated boundary-layer
thickness for both sites, while small-scale turbulent features were a function of the complexity of the upwind terrain. Evidence
of a multi-scale turbulent structure was obtained at the more complex terrain site, while an assessment of the three-dimensional
isotropy assumption in the inertial subrange of the spectrum showed anisotropic turbulence at the less complex site and evidence
of isotropic turbulence at the more complex site, with a spectral ratio convergence deviating from the 4/3 or unity values
suggested by previous theory and practice. Existing neutral spectral models can represent locations along the ridge top with
simple upwind complexity, especially for the vertical wind spectra, but sites with more orographic complexity and strong vertical
wind speeds are often poorly represented using these models. Measured spectra for the two sites exhibited no significant diurnal
variation and very similar large-scale and small-scale turbulent length scales for each site, but the turbulence energy measured
by the variances revealed a strong diurnal difference. 相似文献
8.
Peyman Afzal Hamid Harati Younes Fadakar Alghalandis Amir Bijan Yasrebi 《Chemie der Erde / Geochemistry》2013
The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416 ppm, 23 ppm and 71 ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data. 相似文献
9.
Travel time computations using a compact eikonal equation for vertical transverse isotropic media 
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下载免费PDF全文 Eikonal solvers often have stability problems if the velocity model is mildly heterogeneous. We derive a stable and compact form of the eikonal equation for P‐wave propagation in vertical transverse isotropic media. The obtained formulation is more compact than other formulations and therefore computationally attractive. We implemented ray shooting for this new equation through a Hamiltonian formalism. Ray tracing based on this new equation is tested on both simple as well as more realistic mildly heterogeneous velocity models. We show through examples that the new equation gives travel times that coincide with the travel time picks from wave equation modelling for anisotropic wave propagation. 相似文献
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