The phase lag of temperature behind global solar radiation over Egypt     

F. M. El-Hussainy  K. S. M. Essa 《Theoretical and Applied Climatology》1997,58(1-2):79-86

Summary The relation between the air temperature and the global solar radiation, which can be conveniently represented by the three characteristics: mean, amplitude and phase lag of the first harmonic of global radiation and air temperatures. A good correlation between the air temperature and the solar radiation has been found when the phase lag between them is nearly of 30 days.With 6 Figures  相似文献   

On the relation between cloud cover amount and sunshine duration     

Khaled S. Essa  Soad M. Etman 《Meteorology and Atmospheric Physics》2004,87(4):235-240

Summary The total cloud cover is deduced from measurements of monthly mean averages of the percent of possible sunshine duration at three locations in Egypt, Cairo, Bahtim and Sedi-Barrani stations during the period 1987–1995. This sunshine-derived total cloud cover (C_s) is compared to conventional ground-based observations of total cloud covers (C_g) made by meteorological observers. A linear relationship between the two estimates is calculated, and the difference between the two estimates as a function of C_s and C_g is fitted with a least-squares linear equation. It is found that on the average the sunshine-derived values of total cloud cover are about 7% lower than the corresponding ground-based estimated of total cloud cover. Both of these parameters are mainly used in solar radiation models and the error sources are mainly depending upon the way to describe sky cover.  相似文献   

A Least-squares Approach to Depth Determination from Numerical Horizontal Self-potential Gradients     

E. M. Abdelrahman  H. S. Saber  K. S. Essa  M. A. Fouda 《Pure and Applied Geophysics》2004,161(2):399-411

We have developed a least-squares minimization approach to depth determination of a buried ore deposit from numerical horizontal gradients obtained from self-potential (SP) data using filters of successive window lengths (graticule spacings). The problem of depth determination from SP gradients has been transformed into the problem of finding a solution to a nonlinear equation of the form f(z)=0. Formulas have been derived for vertical and horizontal cylinders and spheres. Procedures are also formulated to estimate the electrical dipole moment and the polarization angle. The method is applied to synthetic data with and without random noise. Finally, the validity of the method is tested on two field examples. In both cases, the depth obtained is found to be in a very good agreement with that obtained from drilling information.  相似文献   

Salinisation des nappes côtières : cas de la nappe nord du Sahel de Sfax,Tunisie     

Rouaida Trabelsi  Moncef Zaïri  Habib Smida  Hamed Ben Dhia 《Comptes Rendus Geoscience》2005,337(5):515-524

The intensive agricultural and economic activities induce the increase of the risk of groundwater quality degradation through high groundwater pumping rates. The salinization and contamination are the main sources of this pollution, especially in coastal aquifers. The explanation of the origin of salinity for the shallow aquifer of Northern Sahel of Sfax was analysed by a chemical study of the groundwater main compounds. The partitioning of groundwaters into homogenous groups is undertaken by graphical techniques, including a Stiff pattern diagram, an expanded Durov diagram and several binary diagrams. The study indicates the presence of various salinization processes. In the recharge area, salinization is the result of dissolution/precipitation of the aquifer formation material (group I). The irrigation water return and the intensive pumping have been identified as major sources of salinization in the south by direct cation exchange and mixing reactions (groups II and III). The anomaly of high groundwater salinity observed near the Hazeg zone was explained by the presence of a seawater intrusion in this area. This hypothesis is related to the high chloride concentration, to the presence of inverse cation exchange reactions (group IV), and to the piezometric level inferior to sea level. To cite this article: R. Trabelsi et al., C. R. Geoscience 337 (2005).  相似文献   

Structure de socle,sismostratigraphie et héritage structural au cours du rifting au niveau de la marge d'Ifni/Tan-Tan (Maroc sud-occidental)     

Naïma AbouAli  Mohamad Hafid  El Hassane Chellaï  Mohamed Nahim  Mahmoud Zizi 《Comptes Rendus Geoscience》2005,337(14):1267-1276

Seismic reflection profiles from the Ifni/Tan-Tan Atlantic margin of southern Morocco, interpreted in the light of well data and field geology from the Western Anti-Atlas, allowed us to establish the seismostratigraphic framework of the syn-rift series and to reveal (i) a compressional structural style in the pre-Triassic basement similar to that established in the adjacent outcropping onshore basement but with an opposed western vergence, (ii) the importance of inherited anterior structures in the formation of Triassic-Liassic rift structures and (iii) an east–west propagation of these rift structures. To cite this article: N. AbouAli et al., C. R. Geoscience 337 (2005).  相似文献   

Strains Induced in Urban Structures by Ultra-High Frequency Blasting Rock Motions: A Case Study     

C. H. Dowding  E. Hamdi  C. T. Aimone-Martin 《Rock Mechanics and Rock Engineering》2016,49(10):4073-4090

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Impacts of a large Sahelian city on groundwater hydrodynamics and quality: example of Niamey (Niger)     

Aïssata B. Hassane  Christian Leduc  Guillaume Favreau  Barbara A. Bekins  Thomas Margueron 《Hydrogeology Journal》2016,24(2):407-423

The management of groundwater resources is very important in the semiarid Sahel region, which is experiencing rapid urban development. Impacts of urbanization on groundwater resources were investigated in the unconfined aquifer of the Continental Terminal beneath the city of Niamey, Niger, using water level and chemical data. Hydrodynamic and chemical changes are best described by a combination of factors including the historical development of the city, current land use, water-table depth and topography. Seasonal groundwater recharge occurs with high spatial variability, as indicated by water-level monitoring in all wells, but there was no interannual trend over the 5-year study period. Groundwater salinity shows high spatial variability and a minor rising trend. The highest salinity is in the old city centre, with Na–NO₃ dominant, and it increases seasonally with recharge. Salinity is much lower and more variable in the suburbs (Ca–HCO₃, Ca–NO₃, and Na–NO₃ dominant). Nitrate is the main ionic contaminant and is seasonally or permanently above the international guidelines for drinking water quality in 36 % of sampled wells, with a peak value of 112 mg L^?1 NO₃–N (8 meq L^?1). Comparison of urban and rural sites indicates a long-term increase in groundwater recharge and nitrate enrichment in the urban area with serious implications for groundwater management in the region.  相似文献   

An Alternative Protocol for Single Zircon Dissolution with Application to (U‐Th‐Sm)/He Thermochronometry          下载免费PDF全文

Bouchaïb Tibari  Arnaud Vacherat  Martin Stab  Raphaël Pik  Delphine Yeghicheyan  Pascal Hild 《Geostandards and Geoanalytical Research》2016,40(3):365-375

Zircon (U‐Th‐Sm)/He (ZHe) thermochronometry is a powerful tool that has been widely used in geology to constrain the exhumation histories of orogens. In this study, we present an alternative protocol for dissolving zircon grains for determination of parent nuclides. This new alkali fusion procedure developed at the SARM (Service d'Analyse des Roches et des Minéraux) in Nancy, France, is fast (requiring only 2 d, including cleaning steps) and offers several advantages over conventional methods by avoiding: (i) use of HF pressure dissolution and (ii) complete removing of grains from the metal microvials. After dissolution, U, Th and Sm were measured using an ICP‐MS. We tested the new procedure on two different ZHe reference materials, the Fish Canyon Tuff and Buluk Tuff; these provided precision values for ZHe‐age estimations of 9 and 6% (1s), respectively. In addition, using this method, zircons from the Buluk Tuff are shown to be chemically more homogenous and more suitable for assessing the uncertainty of the entire integrated procedure.  相似文献   

Impact of spate irrigation of flood waters on agricultural drought and groundwater recharge: case of Sidi Bouzid plain,Central Tunisia     

Hamdi Monji  Louati Dhouha  Majdoub Rajouene  Abida Habib 《Arabian Journal of Geosciences》2016,9(15):653

In Sidi Bouzid plain, rainfall alone is insufficient to satisfy crop water requirements. Within this framework, and in order to improve water resources in the region, the Tunisian State adopted non-conventional water mobilization techniques, among which artificial spate irrigation. The objective of the study is to evaluate the impact of spate irrigation of flood water on the mitigation of agricultural drought and the enhancement of groundwater recharge. Annual and monthly rainfall data as well as flood water volumes were monitored. The study focused on the groundwater drawdown monitoring. Results showed a high flood water contribution to crop water requirements that exceeded rainfall. This water prevented drought in the spate perimeters. The groundwater drawdown was found to fluctuate over time, with an average decreasing rate of 0.4 to 0.5 m/year. Groundwater recharge was found to be highly correlated with flood water contribution through spate irrigation (R ² = 84 %). Out of the spate zone, a high decrease in the groundwater level was noted. The lowest rate of 1 m/year was that of the farthest piezometer from the spate perimeters. This is influenced by the excessive pumping out of the spate zone. In 1980, groundwater flew from the west to the east. In 2015, the flow movement from the east to the center of the plain did not change due to the presence of the spate perimeters. Nevertheless, excessive pumping around sabkhas changed the flow directions at the outlet zone. A variation in groundwater salinity was observed in both space and time. In 1975, salinity was very low. The outlet zone was the most affected where the drawdown reached several meters, causing saltwater intrusion from the surrounding sabkhas.  相似文献   

Correlation of the Meishucunian Stage in South Asia     

M.D.Brasier  B.Hamdi 《《地质学报》英文版》1989,63(1):1-9

The determination of boundary points and their correlation are prerequisites for defining the PrecambrianCambrian boundary and the intercontinental correlation. A large number of good Precambrian-Cambrian boundary sections in South Asia not only possess the conditions for selection of a boundary stratotype, but also provide the basis for the long-distance correlation of those boundary sections.Through a detailed study of the latest data obtained from the typical sections in South China, the Lesser Himalaya Mountains and the Alborz Mountains. the locations of boundary points have been defined, and a correlation scheme is proposed, which contributes to the solution of the problem of worldwide correlation of boundary sections.  相似文献