3,332 research outputs found

    El Hermanito: El Niño's overlooked little brother in the Atlantic

    Get PDF
    An oscillation with a period of about 30 months has been identified in the equatorial Atlantic by analyzing sea surface temperature (SST) observations for the period 1949-1991. The 30-month time scale was also found in numerical simulations with an atmospheric general circulation model (AGCM) that was forced by these SSTs and a coupled ocean atmosphere general circulation model (CGCM). Consistent with the theory of tropical air-sea interactions, the Atlantic oscillation (El Hermanito) is an inherently coupled air-sea mode and can be viewed as the Atlantic analogon of the El Nino/Southern Oscillation (ENSO) phenomenon in the equatorial Pacific. El Hermanito is an internal Atlantic mode and appears to be independent of the quasi-biennial (QB) variability observed in the tropical Indian and Pacific Oceans. The discovery of El Hermanito is important to the prediction of Atlantic climate anomalies. (orig.

    Preparation and Characterization of New Magnetic Montmorillonite Clay Mineral by Intercalation of Iron Oxides in West Iraqi Layered Bentonite

    Get PDF
    A new magnetic montmorillonite hybrid materials of iron (Fe II, Fe III) with Iraqi (Traifawi) montmorillonite were synthesized by mixing 15 g. of H – form initiated montmorillonite with 100 ml saturated aqueous solutions of different percent ratios of ferric and ferrous chlorides (FeCl3 & FeCl2) with continuous agitation at 60ºC, and the mixture is allowed to react for 24 h. to ensure maximum interlayer (Fe+3 & Fe+2) cations intercalation. The resulting Fe – intercalated montmorillonite solids were separated by centrifugation, washed several times with deionized water to free Hydrochloric acid (HCl), dried at 100 ºC for 24 h. (Fe II, Fe III)  –montmorillonite was characterized by Magnetic susceptibility measurement, X-ray diffraction (XRD), FT-IR spectroscopy, and scanning electron microscopy (SEM). The intercalated bentonite samples show high Magnetic susceptibilities due to increment or decrement of Magnetite and Hematite content in these clay samples. All the XRD patterns of iron (Fe II, Fe III) montmorillonite nanocomposites shows a red shift in the position of Montmorillonite mineral main peak due to the emergence of new magnetic clay mineral by intercalation of (Fe II, Fe III) in montmorillonite. Also the clay reflections, present some additional peaks that obviously originate from iron oxides (Hematite Fe2O3), and (Magnetite Fe3O4). FT-IR patterns of (Fe II, Fe III) – montmorillonite samples noticed the appearance of new peaks belongs to (Hematite) Fe2O3 stretching vibration, Fe-O stretching vibration, and (Magnetite Fe3O4) stretching vibration. SEM images of (Fe II, Fe III) – montmorillonite samples showed a change in the nature of the Montmorillonite clay surface. Keywords: Intercalation, West Iraqi, Magnetic Montmorillonite, Layered Bentonite

    Preparation and Characterization for a New ZnO - Montmorillonite Hybrid from Iraqi (Traifawi) Clay Minerals

    Get PDF
    A new hybrid materials of zinc oxide with Iraqi (Traifawi) montmorillonite were synthesized by mixing 15 g. of H – form initiated montmorillonite with 100 ml saturated aqueous solution of Zinc chloride (ZnCl2) with continuous agitation at 60 ºC, and the mixture was allowed to react for 24 h. to ensure maximum interlayer Zn+2 cations intercalation. The resulting Zn – intercalated montmorillonite solid was separated by centrifugation, washed several times with deionized water for free (HCl), dried at 100 ºC for 24 h. and calcined at 900 ºC using Muffle Furnace. ZnO –montmorillonite hybrid was characterized by X-ray diffraction (XRD), FT-IR spectroscopy, scanning electron microscopy (SEM), and Fluorescence spectroscopy. The appearance of the reflections due to ZnO crystal in the XRD patterns of ZnO–montmorillonite and Zn – montmorillonite was ascribed to the formation of ZnO and Zn+2 ions on the solid surfaces. ZnO – montmorillonite hybrid (SEM) images show the flower-shaped structures on the external surface of clay mineral in a complete flower like morphology composed with sharp tipped hexagonal Nano rods. The enhancement in emission intensity of the zinc oxide hybrids may be probably due to increase in oxygen vacancies defect arose by the surrounding environment of montmorillonite. Keywords: Characterization, Iraqi (Traifawi), ZnO - Montmorillonite, hybrid

    Atlantic versus Indo-Pacific influence on Atlantic-European climate

    Get PDF
    The influence of the Atlantic and Indo-Pacific oceans on Atlantic-European climate is investigated by analyzing ensemble integrations with the atmospheric general circulation model ECHAM4 forced by anomalous sea surface temperature and sea ice conditions restricted to the Atlantic (AOGA) and Indo-Pacific (I+POGA) oceans. The forcing from both the Indo-Pacific and Atlantic oceans are important for the generation of the sea level pressure (SLP) variability in the Atlantic region in the boreal winter season. Over the North Atlantic the SLP response in the I+POGA experiment projects on the North Atlantic Oscillation, while it projects on the East Atlantic Pattern in the AOGA experiment. In both experiments (I+POGA and AOGA) a quadrupole-type 500 hPa height anomaly pattern is simulated which emerges from the tropical Pacific and Atlantic oceans, respectively. In boreal summer the influence of the Atlantic Ocean dominates the SLP response in the Atlantic region. The tropical North Atlantic is a key region in forcing the SLP response over the Caribbean Sea in this season

    Qualitative and quantitative determination of lignin in different types of Iraqi Phoenix dactylifera Date palm pruning woods

    Get PDF
    The target of this study is to find analytical data base for Iraqi phoenix date palm pruning woods, which produced by pruning process at the season of date palm production. Lignin has been extracted and purified for five  types of Iraqi date palm using Klason lignin method. The weight of the extracted lignin ranged from (0.473 g – 0.600 g) and the lignin % ranged from (23.5 – 30). The other ingredients (waxes, oils, resin, and proteins of wood gums) % ranged from (11.2 – 53.5). FT– IR Characterization showed that the (-OH) phenolic group appear in Digal lignin structure only and dis appear in other lignin samples, and the (4-O-5 inter monomeric lignin linkage) showed moderate to weak  intensity peaks for all studied samples except the Humrani sample at (1271 cm-1) has a strong intensity peak. Also (DODO inter monomeric lignin linkage) showed strong intensity peaks for each (Humrani at 1116 cm-1, and Tibarzal at 1111 cm-1). UV – Vis. Characterization showed that the lowest absorption maximum (267 nm) corresponds to Basrawi lignin sample, While the highest absorption maximum (297 nm) corresponds to Tibarzal lignin sample. Keywords: Qualitative and quantitative determination , pruning woods, lignin, Phoenix dactylifera

    A review of predictability studies of the Atlantic sector climate on decadal time-scales

    Get PDF
    This review paper discusses the physical basis and the potential for decadal climate predictability over the Atlantic and its adjacent land areas. Many observational and modeling studies describe pronounced decadal and multidecadal variability in the Atlantic Ocean. However, it still needs to be quantified to which extent the variations in the ocean drive variations in the atmosphere and over land. In particular, although a clear impact of the Tropics on the midlatitudes has been demonstrated, it is unclear if and how the extratropical atmosphere responds to midlatitudinal sea surface temperature anomalies. Although the mechanisms behind the decadal to multidecadal variability in the Atlantic sector are still controversial, there is some consensus that some of the longer-term multidecadal variability is driven by variations in the thermohaline circulation. The variations in the North Atlantic thermohaline circulation appear to be predictable one to two decades ahead, as shown by a number of perfect model predictability experiments. The next few decades will be dominated by these multidecadal variations, although the effects of anthropogenic climate change are likely to introduce trends. Some impact of the variations of the thermohaline circulation on the atmosphere has been demonstrated in some studies so that useful decadal predictions with economic benefit may be possible

    The Coupled GCM ECHO-2. Part I: The Tropical Pacific

    Get PDF
    In this paper the performance of the global coupled general circulation model (CGCM) ECHO-2, which was integrated for 10 years without the application of flux correction, is described. Although the integration is rather short, strong and weak points of this CGCM can be clearly identified, especially in view of the model's performance of the annual cycle in the tropical Pacific. The latter is simulated with more success relative to the earlier version, ECHO-I. A better representation of the low-level stratus clouds in the atmosphere model associated with a reduction in the shortwave radiative flux at the air-sea interface improved the coupled model's performance in the southeastern tropical oceans, with a strongly reduced warm bias in these regions. Modifications in the atmospheric convection scheme also eliminated the AGCM's tendency to simulate a double ITCZ, and this behavior is maintained in the CGCM simulation. Finally, a new numerical scheme for active tracer advection in the ocean model strongly reduced the numerical mixing, which seems to enhance considerably the level of interannual variability in the equatorial Pacific. One weak point is an overall cold bias in the Tropics and midlatitudes, which typically amounts to 1°C in open ocean regions. Another weak point is the still too strong equatorial cold tongue, which penetrates too far into the western equatorial Pacific. Although this model deficiency is not as pronounced as in ECHO-1, the too strong cold tongue reduces the level of interannual rainfall variability in the western and central equatorial Pacific. Finally, the interannual fluctuations in equatorial Pacific sea surface temperatures (SSTs) are too equatorially trapped, a problem that is also found in ocean-only simulations. Overall, however, the authors believe that the ECHO-2 CGCM has been considerably improved relative to ECHO-1

    Perancangan Sistem Autonomous Quadcopter

    Get PDF
    Paper ini mengusulkan sebuah perancangan sistem autonomous quadcopter. Quadcopteradalah sejenis pesawat terbang yang memiliki empat motor sebagai penggerak utamanya.Quadcopter memiliki kemampuan untuk lepas landas, hover, terbang manuver dan mendaratbahkan ditempat yang memiliki ruang terbatas. Sistem autonomous quadcopter yang dibangundidesain untuk memiliki kemampuan mengendalikan sistem secara mandiri. Sistem tersebutdiupayakan memiliki seminimal mungkin pengendalian dari user. Semua elemen autonomousquadcopter akan dijelaskan dalam paper ini; termasuk struktur mekanik, sistem kontrol, komputer,sensor, actuator dan sumber energinya. Sistem tersebut juga dirancang agar dapat di bekerja padaarea out door. Pengujian dalam penelitian ini dilakukan fokus terhadap sensor Accelerometer dansensor Gyroscope. Berdasarkan hasil pengujian, rentang nilai ADC sensor gyroscope dengankemiringan sudut 0 hingga 180 adalah 67 sampai 101. Sedangkan pengujian pada kecepatankeempat motor dengan nilai tegangan yang sama, terdapat selisih kecepatan dari beberapa motordengan nilai maksimal 2
    • …
    corecore