Modeling anomalous radar propagation using first-order two-state Markov chains

In this paper, it is shown that radar echoes due to anomalous propagations (AP) can be modeled using Markov chains. For this purpose, images obtained in southwestern France by means of an S-band meteorological radar recorded every 5 min in 1996 were considered. The daily mean surfaces of AP appearing in these images are sorted into two states and their variations are then represented by a binary random variable. The Markov transition matrix, the 1-day-lag autocorrelation coefficient as well as the long-term probability of having each of both states are calculated on a monthly basis. The same kind of modeling was also applied to the rainfall observed in the radar dataset under study. The first-order two-state Markov chains are then found to fit the daily variations of either AP or rainfall areas very well. For each month of the year, the surfaces filled by both types of echo follow similar stochastic distributions, but their autocorrelation coefficient is different. Hence, it is suggested that this coefficient is a discriminant factor which could be used, among other criteria, to improve the identification of AP in radar images.     

Sea level in the Mediterranean Sea: seasonal adjustment and trend extraction within the framework of SSA

The sea level change is a crucial indicator of our climate. The spatial sampling offered by satellite altimetry and its continuity during the past years are the major assets to provide an improved vision of the Mediterranean sea level changes. In this paper, an automatic signal extraction approach, based on Singular Spectrum Analysis (SSA), is utilized for analysis and seasonal adjustment of the Mediterranean Sea level series. This automatic approach enables us to overcome the difficulties of visual identification of trend constituents that sometimes we encounter when using the conventional SSA method. The results indicate that the Mediterranean mean sea level is dominated by several harmonic components. The annual signal is particularly strong and almost covers 73.62 % of the original sea level series variation whiles its amplitude is about 15 cm. The extracted trend also indicates that the Mediterranean main sea level has significantly been raised during the period 1993–2012 by 2.44?±?0.4 mm yr^?1. As an important consequence, considering the current situation, if this trend continues, the Mediterranean Sea level will be raised about 22 cm by the end of this century, which makes a dramatic effect on several issues such as land, flora, fauna, and people activities established along the Mediterranean coastlines.     

Method for determining stable isotope ratios of dissolved organic carbon in interstitial and other natural marine waters

A procedure is described for the analysis of the stable carbon isotopic composition of dissolved organic carbon (DOC) in natural waters from marine and higher-salinity environments. Rapid (less than 5 min) and complete oxidation of DOC is achieved using a modification of previous photochemical oxidation techniques. The CO₂ evolved from DOC oxidation can be collected in less than 10 min for isotopic analysis. The procedure is at present suitable for oxidation and collection of 1–5 μmol of carbon and has an associated blank of 0.1–0.2 μmol of carbon.Complete photochemical oxidation of DOC standards was demonstrated by quantitative recovery of CO₂ as measured manometrically. Isotopic analyses of standards by photochemical and high-temperature sealed-tube combustion methods agreed to within 0.3.. Photochemical oxidation of DOC in a representative sediment pore-water sample was also quantitative, as shown by the excellent agreement between the photochemical and sealed-tube methods. The δ¹³C values obtained for pore-water DOC using the two methods of oxidation were identical, suggesting that the modified photochemical method is adequate for the isotopically non-fractionated oxidation of pore-water DOC.The procedure was evaluated through an analysis of DOC in pond and pore waters from a hypersaline microbial mat environment. Concentrations of DOC in the water column over the mat displayed a diel pattern, but the isotopic composition of this DOC remained relatively constant (average δ¹³C = −12.4.). Pore-water DOC exhibited a distinct concentration maximum in the mat surface layer, and δ¹³C of pore-water DOC was nearly 8. lighter at 1.5–2.0-cm depth than in the mat surface layer (0–0.5-cm depth). These results demonstrate the effectiveness of the method in elucidating differences in DOC concentration and δ¹³C over biogeochemically relevant spatial and temporal scales. Carbon isotopic analysis of DOC in natural waters, especially pore waters, should be a useful probe of biogeochemical processes in recent environments.     

Pore Fabric Anisotropy of the Cambrian–Ordovician Nubia Sandstone in the Onshore Gulf of Suez,Egypt: A Surface Outcrop Analog

Natural Resources Research - Integrated studies on pore fabric anisotropy have increased the general understanding of fluid flow patterns through reservoir rocks. In this study, pore anisotropy was...     

Lead sorption onto thermally treated soil samples from Irbid

Open burning of waste at dumpsites sites may alter many physical and chemical properties of underlining soil layers including its ability to retard the migration of potential contaminants, such as lead, through the vadose zone. In this study, lead sorption onto soil samples from Irbid that were subjected to high temperatures has been investigated. These samples were collected from ground surface and heated to temperatures of 25, 70, 100, 200, 225, 250, 275, 300, 400, and 550°C. Based on these temperatures the soil was divided into ten different groups. Each group was first characterized by conducting a set of experiments to estimate the Atterberg limits (liquid limit, plastic limit, and plasticity index), the organic carbon content, and a set of batch experiments to study lead adsorption. Results indicate that the LL, PL, total organic carbon are slightly affected by high temperatures less than 200°C, show an abrupt change between temperature from 200 and 300°C, and then slight change above 300°C. Sorption of lead onto heated samples, however, was not significantly changed. This may be explained by the fact that adsorption of heavy metals mainly occurs onto the soil mineral parts which are slightly affected by the temperature range used in this study.     

Impacts of fossil anisotropy on the electric and permeability anisotropy of highly fossiliferous limestone: a case study

The Middle Eocene Lutetian Samalut formation is among the best examples of anisotropic fossiliferous rocks in Egypt, where the effect of the anisotropic Nummulite Gizehensis fossils on the petrophysical behavior can be traced. The Samalut formation has been sampled and studied at Wadi Feiran in SW Sinai. Petrographically, it is composed of two microfacies; Nummulitic packstone and Fusulinid mudstone. Tight cementation by micro to pseudosparite, aggrading neomorphism and compaction with increasing load pressure are the most important porosity-reducing factors. The anisotropy of the fossil content (λ_F), due to shape and orientation, and its effect on the petrophysical properties were assigned by measuring the lengths of the longest and shortest axes. Petrophysically, both microfacies are characterized by low porosity values (1.47 ≤ \({\emptyset _{{\text{He}}}}\) ≤ 5.29%). The formation resistivity factor (F) and permeability (k) were measured in the horizontal and vertical directions (parallel and perpendicular to the bedding plane, respectively). The studied samples are characterized by high to very high formation resistivity factor (190?≤?F?≤?8938) and relatively very low permeability (0.012?≤?k?≤?0.110 md). The studied samples are characterized by fair to medium electric anisotropy ‘λ_E’, which is attributed to a relatively medium to fair degree of electric foliation. It has been shown that, the fossil shape anisotropy and orientation ‘λ_F’ (1.5?≤?λ_F?≤?3.5) is the main contributor for the electric and permeability anisotropy that corrected for the same porosity value (1.61?≤?λ_EC?≤?2.25 and 1.03?≤?λ_kC?≤?2.04; respectively). Foliation of the studied microfacies has been contributed to the orientation of the fossil remains parallel to the bedding plane. The anisotropy degree is relatively greater for the Nummulitic packstone microfacies than that of the Fusulinid mudstone. The present study refers to the possible anisotropic effect of fossil content (due to shape and orientation) on the petrophysical properties of the studied rocks which may be extended to the anisotropy of reservoir rocks on the bedding scale.     

Mineralogic and Diagenetic Controls on Reservoir Quality of Paleozoic Sandstones,Gebel El-Zeit,North Eastern Desert,Egypt

Natural Resources Research - Studying the mineral composition and petrophysical properties of the Cambro–Ordovician sequence in Gebel El-Zeit indicates that it can be discriminated into four...