Incorporation of planetary boundary-layer processes into numerical forecasting models     

Mohamed S. Smeda 《Boundary-Layer Meteorology》1979,16(2):115-129

A study has been made of the evolution of the planetary boundary layer height (PBLH), the heat flux, and momentum flux using Clarke's Wangara data for a period of two days and two nights, 33/34–34/35. The observed Wangara data are considered as being an output of the first two internal levels of a general circulation model, at 1000 and 2000 m height. A time-dependent equation has been used to forecast, explicitly, the PBLH for both convectively unstable and stable periods. A comparison is made between observed and computed values whenever possible. In the unstable case, the Deardorff model (1974) has been used for the prediction of the unstable PBLH. Part of the stable case study involved a formulation of a time-dependent model for the prediction of the stable PBLH. The solution obtained from the model compared favourably with the results of a model suggested by Khakimov. Contribution number 382.  相似文献   

Incorporation of Planetary Boundary-Layer Processes into Numerical Forecasting Models     

Mohamed S. Smeda 《Boundary-Layer Meteorology》1979,16(3):115-129

A study has been made of the evolution of the planetary boundary layer height (PBLH), the heat flux, and momentum flux using Clarke’s Wangara data for a period of two days and two nights, 33/34-34/35. The observed Wangara data are considered as being an output of the first two internal levels of a general circulation model, at 1000 and 2000 m height. A time-dependent equation has been used to forecast, explicitly, the PBLH for both convectively unstable and stable periods. A comparison is made between observed and computed values whenever possible. In the unstable case, the Deardorff model (1974) has been used for the prediction of the unstable PBLH. Part of the stable case study involved a formulation of a time-dependent model for the prediction of the stable PBLH. The solution obtained from the model compared favourably with the results of a model suggested by Khakimov.  相似文献   

Mercury pollution of Mediterranean sediments around Alexandria,Egypt     

Mahmoud Kh. El-Sayed  Youssef Halim  Hassan M. Abdel-Kader  Mohamed H. Moeness 《Marine pollution bulletin》1979,10(3):84-86

Elemental mercury is associated with industrial wastes discharged through the main effluent pipe of the Chlorine-Alkali plant at El-Max area west of Alexandria. The minimal mercury value of 0.1 ppm dry weight is assumed to be the background level for uncontaminated sediments in the area. Mercury level ranged from 8.02 to 15.5 ppm in the beach sands from the polluted area beyond the plant, and from 0.14 to 1.4 ppm in the bottom sediments off Alexandria.The Chlorine-Alkali plant is obviously the major source of mercury pollution. The contribution of land drainage, agricultural and domestic wastes is insignificant.  相似文献   

A crustal suture and lineament in North Africa — reply     

Richard M. Nagy  Mohamed A. Ghuma  John J.W. Rogers 《Tectonophysics》1977,40(3-4):380-382

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Land cover and land use classification performance of machine learning algorithms in a boreal landscape using Sentinel-2 data   总被引：1，自引：0，他引：1  

Abdulhakim Mohamed Abdi 《地理信息系统科学与遥感》2020,57(1):1-20

ABSTRACT

In recent years, the data science and remote sensing communities have started to align due to user-friendly programming tools, access to high-end consumer computing power, and the availability of free satellite data. In particular, publicly available data from the European Space Agency’s Sentinel missions have been used in various remote sensing applications. However, there is a lack of studies that utilize these data to assess the performance of machine learning algorithms in complex boreal landscapes. In this article, I compare the classification performance of four non-parametric algorithms: support vector machines (SVM), random forests (RF), extreme gradient boosting (Xgboost), and deep learning (DL). The study area chosen is a complex mixed-use landscape in south-central Sweden with eight land-cover and land-use (LCLU) classes. The satellite imagery used for the classification were multi-temporal scenes from Sentinel-2 covering spring, summer, autumn and winter conditions. Using stratified random sampling, each LCLU class was allocated 1477 samples, which were divided into training (70%) and evaluation (30%) subsets. Accuracy was assessed through metrics derived from an error matrix, but primarily overall accuracy was used in allocating algorithm hierarchy. A two-proportion Z-test was used to compare the proportions of correctly classified pixels of the algorithms and a McNemar’s chi-square test was used to compare class-wise predictions. The results show that the highest overall accuracy was produced by support vector machines (0.758 ± 0.017), closely followed by extreme gradient boosting (0.751 ± 0.017), random forests (0.739 ± 0.018), and finally deep learning (0.733 ± 0.0023). The Z-test comparison of classifiers showed that a third of algorithm pairings were statistically different. On a class-wise basis, McNemar’s test results showed that 62% of class-wise predictions were significant from one another at the 5% level or less. Variable importance metrics show that nearly half of the top twenty Sentinel-2 bands belonged to the red edge (25%) and shortwave infrared (23%) portions of the electromagnetic spectrum, and were dominated by scenes from spring (38%) and summer (40%). The results are discussed within the scope of recent studies involving machine learning and Sentinel-2 data and key knowledge gaps identified. The article concludes with recommendations for future research.  相似文献   

Gravity constraints on the structure of the northern margin of Tunisia: implications on the nature of the northern African Plate boundary   总被引：1，自引：0，他引：1  

Chokri Jallouli  Kevin L. Mickus  Mohamed Moncef Turki 《Geophysical Journal International》2002,151(1):117-131

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Migration from Eastern Gezira into greater Khartoum     

Mohamed E. Abu Sin 《GeoJournal》1991,25(1):73-79

This paper is an attempt to investigate the role of rural-urban migration in the population integration process and national identity in Sudan. Although migration is considered as an important mechanism in integration, yet its effect cannot be easily detected if urban life fails to challenge the culture and norms of migrants. In this case study the role of migration is limited by the status of the urban and the purely traditional background of migrants. Population integration is a central issue in the Sudan with its high level of pluralism, ethnic and cultural complexity. It is assumed that migration is an essential factor to challenge such complexity. This paper is part of a research programme financed by the Deutsche Forschungsgemeinschaft (DFG) — Identity in Africa — Processes of Development and Change — initiated and sponsored by H. Ruppert and F. N. Ibrahim, University of Bayreuth.  相似文献   

Effects of soil-structure interaction on seismic response of elevated tanks   总被引：1，自引：0，他引：1  

Medhat A. Haroun  Mohamed K. Temraz 《Soil Dynamics and Earthquake Engineering》1992,11(2)

Models of two-dimensional x-braced elevated tanks supported on isolated footings are analyzed to investigate the effects of dynamic interaction between the tower and the supporting soil-foundation system. Static, dynamic elastic, and dynamic inelastic responses of towers under horizontal ground motions are evaluated. Effects of soil properties, represented by the shear wave velocity, on joint displacements and on member end actions are studied. In general, soil-tower interaction reduces member end actions except near the base of tower.  相似文献   

Palaeomagnetism of the Stephano-Autunian Lower Tiguentourine formations from stable Saharan craton (Algeria)   总被引：1，自引：0，他引：1  

Mohamed El-Messaoud Derder  Bernard Henry  Nacer-Eddine Merabet  Lucien Daly 《Geophysical Journal International》1994,116(1):12-22

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Radiospectrometric and magnetic signatures of a gold mine in Egypt     

Mohamed A. El-Sadek 《Journal of Applied Geophysics》2009,67(1):34-43

The purpose of this research is to study the signatures of a gold mine (Um Salim), located in the Eastern Desert of Egypt, using aeroradiospectrometric and aeromagnetic data. To achieve this goal, reduction-to-pole (RTP), high-pass filtering and analytical signal techniques were applied to the aeromagnetic data. Besides, interpretation of the total-count (TC) radiometric map, the three radioelements (K, eU and eTh) maps and the ternary radioelement composite image were carried out. Moreover, a two-dimensional trend analysis for the structural lineaments as traced from the geologic, total-count radiometric and reduced-to-pole magnetic maps was conducted to define the relationship which might exist between location of the gold mine, lithologies and major structures of the area under consideration.The study revealed that the known gold mine is associated with a high positive magnetic anomaly that trends in the NE direction and a high-amplitude analytic signal. The Um Salim gold mine is associated with very low aeroradiospectrometric levels on the four maps (TC, K, eU and eTh). The location of the gold mine is controlled by the intersection of both NW and NE trends. There are other particular radiospectrometric ratio signatures for gold deposits (eU/eTh, eU/K and eTh/K). Ternary radioelement maps can discriminate also alteration zones in various degrees that correlate with the gold mine. These zones can be used as a diagnostic exploration guide for various types of non-radioactive mineral deposits (e.g., copper and gold). Four major tectonic trends were identified that have the following directions: NE, NW, N–S and WNW.  相似文献