Volume 9 ,2007

Temperature contours at 2-m altitude over Egypt , H.A. Kandil et al., 2006.

Building an Accurate Weather Prediction Model for Egypt

An accurate and reliable weather prediction model for Egypt has been made operational at the National Authority for Remote Sensing and Space Sciences (NARSS). To enhance the predictions of such models, remote-sensing observations were integrated in the modeling process such that real-time satellite data are used to initialize, provide boundary conditions for, and verify predictions of the computational models. To face the challenge of producing such high-accurate results at NARSS, three dual-processor 64-bit machines were interconnected using a cost-effective, high performance, packet-communication and switching technology to form a powerful computational cluster. Such a cluster of machines will enable the building of accurate regional climate models for regions of interest to the climate, air pollution and natural resources of Egypt. The integration of remote-sensing observations such as Normalized Difference Vegetation Index (NDVI) greatly enhanced the accuracy of modeling and increased the reliability of the results, which helps in understanding the climate changes and in forecasting the weather in the simulated region. The steps taken to build, improve, and optimize the modeling system are presented. The model was validated through comparisons with weather station's observations over Egypt.

Simulation of Atmospheric Temperature Inversions Over Greater Cairo using the Mm5 Meso-Scale Atmospheric Model

Air pollution episodes have been recorded in Cairo, during the fall season, since 1999, as a result of specific meteorological conditions combined with large quantity of pollutants created by several ground-based sources.

The main reason for the smog-like episodes (black clouds) is adverse weather conditions with low and variable winds, high humidity and strong temperature inversions in the few-hundred meters above the ground. The two important types of temperature inversion affecting the air pollution are surface or ground (radiation) inversion and subsidence (elevated) inversion. The surface temperature inversion is associated with a rapid decrease in the ground surface temperature with the simultaneous existence of warm air in the lower troposphere. The inversion develops at dusk and continues until the surface warms again the following day. Pollutants emitted during the night are caught under this "inversion lid." Subsidence inversion forms when warm air masses move over colder air masses. The inversion develops with a stagnating high-pressure system (generally associated with fair weather). Under these conditions, the pressure gradient becomes progressively weaker so that winds become light. These light winds greatly reduce the horizontal transport and dispersion of pollutants. At the same time, the subsidence inversion acts as a barrier to the vertical dispersion of the pollutants. In this study, the Penn State/NCAR meso -scale model (MM5) is used to simulate the temperature inversion phenomenon over Greater Cairo region during the fall season of 2004. Accurate computations of the heat transfer at the surface are needed to capture this phenomenon. This can only be achieved by high-resolution simulations in both horizontal and vertical directions. Hence, for accurate simulation of the temperature inversion over Greater Cairo, four nested domains of resolutions of 27 km, 9 km, 3 km and 1 km, respectively, were used in the horizontal planes. Furthermore, 42 levels were used in the vertical direction to capture the correct surface heat flux and to observe the small changes in the vertical temperature gradient.

The results of the numerical model showed that it is possible to capture both types of temperature inversion during the night and early morning hours. This can be observed from the results of the vertical temperature profile and temperature gradient, which indicate that an inversion system was present over Cairo at a layer extending between 300 m and 800 m above the ground.

Air Pollution Impact on Aerosol Variability Over Mega Cities Using Remote Sensing Technology: Case Study, Cairo, Egypt

Air pollution problems over mega cities differ greatly and are influenced by a number of factors, including topography, demography, meteorology, level and rate of industrialization and socioeconomic development. Cairo is considered a key city for economy, education, politics, industry and technology in the Middle East. Increasing business and industrial activities in the city accompanied by shortage of the institutional capabilities for monitoring and control, in addition to environmental impact negligence that prevails over many of the production sectors, have contributed to excessive air pollution problems that have reached the level of crisis. A contributor to this problem is natural and man made effects such as dust and aerosols uptakes. Such pollution episodes are observed during October showing the so called "Black Cloud". Such pollution leads to wide variability of aerosols behavior over Cairo. Hence, aerosol related parameters obtained from satellite measurements have been studied here. Aerosol Optical Depth (AOD) behavior showed a dual maxima nature in each year from 2000 till 2005 during the months of (April, May) and October confirming dust and air pollution events, respectively. Such behavior is confirmed by the high negative correlation with the aerosol Fine Mode Fraction (FMF) reaching -0.75. FMF product confirms a higher value during the months of October representing the Black Cloud episodes due to fine particles contribution in these events rather than during the dust events. However, lower values are observed in the last two years due to the new control measures enforced by the government. The difference between the AOD and FMF showed a higher contribution of the fine grains during the Black Cloud events rather than coarser grains during dust events as expected. Among the sources known to contribute to the black cloud formation is the fire bums over the Nile Delta region during the months of September and October of each year. Using the fire count product locations of hot spots are identified during the months of October of the years 2001-2004. The monthly variability of the fire count showed abrupt changes during the months of October compared to other months of the year confirming bums contribution in the Black Cloud formation.

Improving Change Detection Capability Using Fuzzy Logic for Remote Sensing Images

In this paper we introduce an approach to improve the change detection capability for remote sensing images using fuzzy logic. In our approach we attempt to overcome the limitations of the post classification comparison approach by involving an independent fuzzy classification of digital SPOT satellite images from different dates, then posing logical queries over those classified images. Using fuzzy logic for post classification comparison provides partial class assignment in regions where there is a gradual transition from one class to another. We undertake the analysis of the changes to find the criteria to improve change detection capability. Also our approach not only detects changes and their nature, but also can detect the orientation of such changes. The proposed approach is implemented on SPOT subscene covering EI-Manzala Lake in northern Egypt, detecting the changes in the period between 1990 and 2000.

Hyper-spectral Analysis of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) Data: An Example from the Neoproterozoic Um Nar Banded Iron formation (Bif), Egypt

Hyper-spectral analysis of the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data is used to map lithological units and geological structures associated with the Neoproterozoic Um Nar Banded Iron Formation (BIF) in the Central Eastern Desert of Egypt, in the northwestern part of the Neoproterozoic Arabian-Nubian Shield. The Neoproterozoic rocks covering the Um Nar area include ophiolitic melange, sheared granite, and the BIF and the hosting volcano-sedimentary rocks. Hyper-spectral analysis of ASTER data includes: (1) Extraction of spectral end-members through N-dimensional visualization; (2) Application of Minimum Noise Fraction (MNF) transform and Pixel Purity Index (PPI) to evaluate the validity of spectral end-members; and (3) Hyper-spectral classification including Spectral Angle Mapper (SAM), Spectral Feature Fitting (SFF), Linear Spectral Un-mixing (LSU), and Matched Filtering (MF). The draped SAM RGB color combination image on the ASTER DEM, in order to generate three dimensional (3D) perspective view, has advanced the lithological and structural mapping. This work concludes that SAM is the most effective classification for mapping different lithological units of the study area. This is because most of the spectral end-members lack distinctive spectral features and because SAM is insensitive to changes in pixel illumination. Moreover, because of the difficulty of extracting all end-members included in the study area, LSU produced limited results compared to MF which does not require all spectral end-members to be identified. The interpretation driven from hyper-spectral analysis, allowed refining previous lithological and structural interpretations including better defined spatial distribution of various lithological units as well as better delineation of ductile and brittle geological structures in the study area.

Determining Priority Areas for the Sustainable Development of Wadi El Assiuti, Eastern Desert, Egypt, Using Hydrogeological, Remote Sensing and GIS Criteria

Wadi El-Assiuti dry drainage basin is one of the largest valleys in the Eastern Desert of Egypt. It comprises in its downstream part valuable lands for cultivation and is considered as a developmental corridor for the over-populated Assiut Governorate. Groundwater development and utilization have reached alarming rates in Wadi El-Assiuti new cultivated lands. The Pleistocene groundwater aquifer is the predominant source of water supply and over 85 boreholes are found in the area. High rates of abstraction and a lack of adequate recharge have caused drastic over consumption and operational difficulties. Proper management strategies are required. This paper suggests management strategies in terms of groundwater-surface water conjunctive use and water harvesting plan, which aimed at improving the situation. The author investigated and determined the evolution of developmental activities by remote sensing change detection and image processing techniques. The priority areas for development were determined by several ground truth (collecting data on boreholes) and GIS techniques. These techniques designated the south western part of the study area as a priority areas suitable for the developmental activities. These areas were determined according to certain parameters; i. e. shallow depth to water, satisfactory low total dissolved solids (TDS), low sodium adsorption ratio (SAR), high hydraulic conductivity (K) and big tested aquifer useful thickness.

Slope Stability Studies by Multidisciplinary Tools Along Al-Baha Mountainous Road, Southern Saudi Arabia

Modem descent highways network are linking uplands with lowlands at the mountainous regions along the Red Sea coast of Saudi Arabia. Al-Baha descent study was an urgent task. More than eight descents are passing through an extremely rugged terrain with harsh weather and rainfall. Along the Al-Baha descent road, many failures frequently occur causing losses in lives and infrastructures. Satellite image assessment, studies of geological, geomorphological features, and geotechnical properties, in addition to rock slope stability analyses technique enhance our understanding of evaluating such terrain. Image processing of Landsat- TM and SPOT -PLA digital data were carried out in order to produce lineament maps. Lineaments were interpreted based on satellite imagery and maps were prepared for both Al-Baha region and Al-Baha descent areas, analyzed, and results were compared with the field conditions. Active remedial measures along the descent vary according to the rock type, joint intensity, slope angle, and terrain condition. Hazards maps generated by using GIS technique, Arc View program, made a valuable contribution to mitigation of the rock slopes susceptible to failure. Based on the results of this work, some additional remedial measures are suggested.

Integrated Remote Sensing and GIS for Proposing Groundwater Recharge Locations: Case Study at West El-Nubariya Canal, Egypt

West Delta, especially the areas located at west EI-Nubariya Canal, is suffering from groundwater deterioration due to different reasons. Application of groundwater recharge to sustain water quality and quantity is thus essential. The aim of this study is to propose suitable locations for recharging the groundwater Quaternary aquifer.

The technique used depends on using satellite remote sensing imagery that plays an important role in providing recent information about the latest land-use classes, surface structures (fractures and joints) and drainage network in the area.

The methodology of this work depends on: 1-Producing a classified land-use map using Landsat-7 ETM+ imagery (2003) applying the supervised classification technique and 2-Developing a "Weighted Suitability Model" using GIS technique for proposing suitable locations for applying groundwater recharge, depending on a number of input thematic maps. The main input criteria are: a suitable land-use class, proximity to canals, topography of the area, soil permeability, distance from urban areas, availability of a natural drainage network and availability of water surrounding the area of interest, in addition to the aquifer characteristics. Each criterion is assigned a weight (1-5) depending on its importance in the proposed model. According to these criteria, suitable locations for recharge, different from those where a previous experimental study took place in the period 1996-1999, are here proposed.

Hydrogeology of Siwa Oasis and Landuse Map

Groundwater represents the main source of water supply in Siwa Oasis. The sedimentary succession comprises different water-bearing formations. Three aquifers bear groundwater ranging in its salinity from fresh water to brine one. These aquifers are, the Quaternary deposits, the Miocene carbonate, the Eocene carbonate, the Upper Cretaceous, the Cretaceous Nubian Sandstone beside Carboniferous, Devonian, Silurian and Cambrian-Ordovician sandstone aquifers. The Paleozoic sandstone has brine water but the Mesozoic one (Cretaceous Nubian Sandstone) has fresh one. The Cretaceous Nubian Sandstone represents the source of exploited water in the area, where it recharges the overlying carbonate aquifers. Fifty seven wells are included in the present study to reveal the hydrogeologic conditions of the oasis. The fractured carbonate aquifers represent the main exploitable aquifers due to its availability for the farmers in spite of its low quality. The water of these aquifers has a wide range of salinity ranging from 2377 ppm to > 17000 ppm depending on the depth of aquifer and the nature of facies and fracture of the rock. The Cretaceous Nubian Sandstone aquifer represents the main source of water in the area where it bears fresh water (>1000 ppm). The flow of Nubian Sandstone water is mainly to area of high discharge, i.e. to the west. The groundwater of Quaternary and fractured carbonates (Eocene and Miocene carbonates) reflects leaching processes (secondary salinity) and that of the Nubian Sandstone reflects meteoric origin and recharge during the pluvial period. On the other hand, the groundwater is evaluated for different purposes. Depending on the present geomorphological and hydrogeological studies and the previous pedological studies a land-use map was constructed.

Application o Track Etch Detectors in U- Exploration at Abu Zarab Area, Southwest Sinai, Egypt

Abu Zarab area represents one of the most important locations, from the mineralogical point of view, at southwest Sinai, since it hosts some ferromagnesian ore bodies and uranium mineralization. The present work aims to use gamma-ray spectrometry (active technique) and track etch detector (passive technique) as a tool in U-exploration at Abu Zarab area.

The content of the radio-elements; U, Th, Ra and K in 27 representative samples from different rock sequences of the study area were measured radiometrically. This technique reveals that the ferruginous siltstone with clay intercalation is the most important rock sequence, from the radioactive point of view, since its U- content reaches up to 237 ppm with 85 ppm in the average. This was attributed to the presence of xenotime mineral. Radon (Rn-222) concentration was determined in about 39 measuring stations in the study area using CR-39 solid-state nuclear track detectors (SSNTDs). The minimum and maximum obtained values are in between 52.59 ± 8.33 Bqm-3 and 1165.66 ± 117.61 Bqm-3, with relative standard deviation (RSD) ranging between 10 % and 16%. As a result of this study two regions of anomalous radon levels were detected, where the track density ranging from three to fourteen times as compared with the background. The average of the background in the studied trenches is 81.49 ± 11.11 Bqm-3. The present study indicates that there is a good match between the results obtained from the track etches detectors (passive technique) and that obtained from the NaI detector (active technique).