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Journal articles on the topic 'Saharan desert'
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1
Nisantzi, A., R. E. Mamouri, A. Ansmann, G. L. Schuster, and D. G. Hadjimitsis. "Middle East versus Saharan dust extinction-to-backscatter ratios." Atmospheric Chemistry and Physics Discussions 15, no. 4 (2015): 5203–40. http://dx.doi.org/10.5194/acpd-15-5203-2015.
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Abstract. Four years (2010–2013) of observations with polarization lidar and sun/sky photometer at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, were used to compare extinction-to-backscatter ratios (lidar ratios) for desert dust from Middle East deserts and the Sahara. The complex data analysis scheme is presented. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan desert dust lidar ratios. We found values from 44–65 sr with a mean value of 52.7 sr for Saharan dust and from 35–46 sr with a mean value of 41.1 sr for Middle East dust. The presented data analysis, however, also demonstrates the difficulties in identifying the optical properties of dust even during outbreak situations in the presence of complex aerosol mixtures of desert dust, marine particles, fire smoke, and anthropogenic haze.
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Duncan, Clare, Daniela Kretz, Martin Wegmann, Thomas Rabeil, and Nathalie Pettorelli. "Oil in the Sahara: mapping anthropogenic threats to Saharan biodiversity from space." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1643 (2014): 20130191. http://dx.doi.org/10.1098/rstb.2013.0191.
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Deserts are among the most poorly monitored and understood biomes in the world, with evidence suggesting that their biodiversity is declining fast. Oil exploration and exploitation can constitute an important threat to fragmented and remnant desert biodiversity, yet little is known about where and how intensively such developments are taking place. This lack of information hinders local efforts to adequately buffer and protect desert wildlife against encroachment from anthropogenic activity. Here, we investigate the use of freely available satellite imagery for the detection of features associated with oil exploration in the African Sahelo-Saharan region. We demonstrate how texture analyses combined with Landsat data can be employed to detect ground-validated exploration sites in Algeria and Niger. Our results show that site detection via supervised image classification and prediction is generally accurate. One surprising outcome of our analyses is the relatively high level of site omission errors in Niger (43%), which appears to be due to non-detection of potentially small-scale, temporary exploration activity: we believe the repeated implementation of our framework could reduce the severity of potential methodological limitations. Overall, our study provides a methodological basis for the mapping of anthropogenic threats associated with oil exploitation that can be conducted across desert regions.
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Lavaysse, Christophe. "Saharan desert warming." Nature Climate Change 5, no. 9 (2015): 807–8. http://dx.doi.org/10.1038/nclimate2773.
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MCDOUGALL, E. ANN. "RESEARCH IN SAHARAN HISTORY." Journal of African History 39, no. 3 (1998): 467–80. http://dx.doi.org/10.1017/s0021853798007233.
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Desert Frontier: Ecological and Economic Change along the Western Sahel, 1600–1850. By JAMES L. A. WEBB JR. Madison and London: University of Wisconsin Press, 1995. Pp. xxvi+227. £40.95 (ISBN 0-299-14330-9); £17.95, paperback (ISBN 0-299-14334-1).In contrast to the desert itself, the Sahara as subject of historical (re)construction is currently displaying signs of health and vitality. It is enticing historians into a range of theoretical and methodological domains deriving from other disciplines, and simultaneously attracting scholars from other disciplines to play out their own explorations around its contours. For a space which seems to have no difficulty occupying well-delineated and identified areas in every genre of cartographical representation, the Sahara is surprisingly difficult to ‘locate’ in academic discourse. Its identity, in current parlance, is a popular focus of speculation and debate, challenging conventional notions of its location, both in time and in space. One of these challenges is engagingly articulated in the recent publication of economic historian James Webb Jr. His Desert Frontier: Ecological and Economic Change along the Western Sahel, 1600–1850, invites wider participation in this ‘search for the Sahara’ and in so doing, encourages broader understanding of just where ‘Saharan studies’ and in particular Saharan history and Saharan society stand in these so-called post-colonial times.
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PETTIGREW, ERIN. "THE HEART OF THE MATTER: INTERPRETING BLOODSUCKING ACCUSATIONS IN MAURITANIA." Journal of African History 57, no. 3 (2016): 417–35. http://dx.doi.org/10.1017/s0021853716000323.
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AbstractThis article examines events involving accusations of bloodsucking in the southwestern Sahara. French colonial archives allow researchers to identify specific cases in time and location; however, this article seeks to address but then move beyond histories of colonial governance. To highlight how communities in the Saharan desert dealt with crises provoked by environmental and social change, this investigation also relies on locally-produced written legal opinions and oral testimony. Emerging from these Saharan sources is one facet of how desert communities envisioned the enchantment of their social worlds and understood difficult periods caused by famine, weak economies, and domestic tensions.
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Nisantzi, A., R. E. Mamouri, A. Ansmann, G. L. Schuster, and D. G. Hadjimitsis. "Middle East versus Saharan dust extinction-to-backscatter ratios." Atmospheric Chemistry and Physics 15, no. 12 (2015): 7071–84. http://dx.doi.org/10.5194/acp-15-7071-2015.
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Abstract. Four years (2010–2013) of observations with polarization lidar and sun/sky photometer at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, were used to compare extinction-to-backscatter ratios (lidar ratios) for desert dust from Middle East deserts and the Sahara. In an earlier article, we analyzed one case only and found comparably low lidar ratios < 40 sr for Middle East dust. The complex data analysis scheme is presented. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan dust lidar ratios. We found values from 43–65 sr with a mean (±standard deviation) of 53 ± 6 sr for Saharan dust and from 33–48 sr with a mean of 41 ± 4 sr for Middle East dust for the wavelength of 532 nm. The presented data analysis, however, also demonstrates the difficulties in identifying the optical properties of dust even during outbreak situations in the presence of complex aerosol mixtures of desert dust, marine particles, fire smoke, and anthropogenic haze.
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Tian, Chuyin, Guohe Huang, Chen Lu, Tangnyu Song, Yinghui Wu, and Ruixin Duan. "Northward Shifts of the Sahara Desert in Response to Twenty-First-Century Climate Change." Journal of Climate 36, no. 10 (2023): 3417–35. http://dx.doi.org/10.1175/jcli-d-22-0169.1.
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Abstract The spatial extent of the Sahara (the largest nonpolar desert) has significant impacts on the livelihood of people residing in its surrounding areas. Despite the fact that climate change would foreseeably impact the location and size of the desert, its future responses (i.e., advance or retreat) are rarely explored in previous studies. Here, through the development of an ensemble Bayesian discriminant analysis approach, we use 10 of the latest high-resolution GCM (global climate model) simulations to document robust annual and seasonal responses of the Sahara Desert to twenty-first-century climate change, with the consideration of modeling uncertainties. We find northward shifts of the Sahara/Sahel and eastern expansion of the nondesert zone under both SSP2–4.5 and SSP5–8.5 scenarios, the former more pronounced in the wet season and the latter in the dry season. Countries located near the Mediterranean may thus experience higher risks of drought, while the projected retreat of the Saharan southern boundary will be beneficial to the local water availability of proximal countries. Significance Statement Given that sub-Saharan Africa is one of the most vulnerable regions to climate change, the Sahara’s expansion would bring unexpected health risks to billions of people. It is thus vital to understand its robust response to global warming. However, previous studies are merely focused on using a simple precipitation threshold as the definition criterion to estimate the varying size of the Sahara Desert. In addition, significant uncertainty in precipitation projections also limits relevant investigations of the Sahara’s future responses. Here, by developing an ensemble Bayesian discriminant analysis approach, we could provide an objective basis for desert identification under large intermodel uncertainty. Further, we find significant northward shifts of both the Sahara and the Sahel, which may induce higher risks of drought over the northwest of North Africa.
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Yeager, Daniel E., and Vernon R. Morris. "Distinguishing Saharan Dust Plume Sources in the Tropical Atlantic Using Elemental Indicators." Atmosphere 15, no. 5 (2024): 554. http://dx.doi.org/10.3390/atmos15050554.
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The Sahara Desert is the largest contributor of global atmospheric dust aerosols impacting regional climate, health, and ecosystems. The climate effects of these dust aerosols remain uncertain due, in part, to climate model uncertainty of Saharan source region contributions and aerosol microphysical properties. This study distinguishes source region elemental signatures of Saharan dust aerosols sampled during the 2015 Aerosols Ocean Sciences Expedition (AEROSE) in the tropical Atlantic. During the 4-week campaign, cascade impactors size-dependently collected airborne Saharan dust particulate upon glass microfiber filters. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis differentiated metal isotope concentrations within filter samples from various AEROSE dust sampling periods. Back-trajectory analysis and NOAA satellite aerosol optical depth retrievals confirmed source regions of AEROSE ’15 dust samples. Pearson correlational statistics of source region activity and dust isotope concentrations distinguished the elemental signatures of North African potential source areas (PSAs). This study confirmed that elemental indicators of these PSAs remain detectable within dust samples collected far into the marine boundary layer of the tropical Atlantic. Changes detected in dust elemental indicators occurred on sub-weekly timescales across relatively small sampling distances along the 23W parallel of the tropical Atlantic. PSA-2 emissions, covering the western coast of the Sahara, were very strongly correlated (R2 > 0.79) with Ca-44 isotope ratios in AEROSE dust samples; PSA-2.5 emissions, covering eastern Mauritania and western Mali, were very strongly correlated with K-39 ratios; PSA-3 emissions, spanning southwestern Algeria and eastern Mali, were very strongly correlated with Fe-57 and Ti-48 ratios. The abundance of Ca isotopes from PSA-2 was attributed to calcite minerals from dry lakebeds and phosphorous mining activities in Western Sahara, based on source region analysis. The correlation between K isotope ratios and PSA-2.5 was a likely indicator of illite minerals near the El Djouf Desert region, according to corroboration with mineral mapping studies. Fe and Ti ratio correlations with PSA-3 observed in this study were likely indicators of iron and titanium oxides from Sahelian sources still detectable in Atlantic Ocean observations. The rapid changes in isotope chemistry found in AEROSE dust samples provide a unique marker of Saharan source regions and their relative contributions to desert outflows in the Atlantic. These elemental indicators provide source region apportionments of Sahara Desert aerosol flux and deposition into the Atlantic Ocean, as well as a basis for model and satellite validation of Saharan dust emissions for regional climate assessments.
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Tadjer, Sid Ahmed, Abdelhakim Idir, and Fathia Chekired. "Comparative performance evaluation of four photovoltaic technologies in saharan climates of Algeria: ghardaïa pilot station." Indonesian Journal of Electrical Engineering and Computer Science 18, no. 2 (2020): 586. http://dx.doi.org/10.11591/ijeecs.v18.i2.pp586-598.
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The aim of this paper is to present an evaluation of the performancerate of four different photovoltaic techniques in the Saharan environment. The purpose of this study is to investigate, analyse, discuss and illustrate the most effective of the different photovoltaic cell technologies (monocrystalline , amorphous silicon , poly-crystalline silicon and cadmium telluridethin film ) installed in Ghardaia which is located in southern of Algeria’s Sahara desert. In order to choose the most suitable technology in the Saharan climate conditions, the energy values produced by the plant were compared to those found by the PVSYST sizing software. The results show that thin-film and amorphous silicon panels produce low illumination, so they are the best choice for the Saharan environment.
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Mekki-Berrada, Abdelwahed. "‘Ayn mika: Traumatic experience, social invisibility, and emotional distress of sub-Saharan women with precarious status in Morocco." Transcultural Psychiatry 56, no. 6 (2018): 1170–90. http://dx.doi.org/10.1177/1363461518757798.
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Morocco has become a permanent transit country for tens of thousands of sub-Saharan migrants heading to Europe. Many of these migrants are women who have a precarious legal status and can no longer reach Europe, whose borders have been considerably securitized since September 11, 2001. They also have no wish to risk their lives again returning south across the Sahara Desert. This paper discusses the results of an exploratory research project conducted in Morocco on the relationships between the sub-Saharan migrant women’s traumatic experiences, social invisibility, and emotional distress in the context of a massive securitization of Euro-Mediterranean borders.
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Elfaleh, Imed. "The Development Of Alternative Tourism In Tunisia: Innovate Or Disappear"! An Example Of Saharan Tourism." International Journal of Arts, Humanities & Social Science 04, no. 12 (2023): 32–41. http://dx.doi.org/10.56734/ijahss.v4n12a4.
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The Tunisian tourist offer has long been standardized and focused on a coastal product. Tourism institutions and actors have shown efforts to diversify this offer, particularly by introducing alternative tourism such as Saharan tourism, where local development's geographical, tourist, and socio-economic opportunities seem obvious. Tourism is one of the world's most important economic activity, having significant economic growth potential for emerging and least developed countries. However, in its current incarnations, it is controlled by foreign operators, and its focus on coastal tourism is unfavorable. In order to attain growth, the nation must develop its travel offerings using a variety of strategies, such as improvement of current solutions, positioning the offer as having value, and surprise the customer. Innovation requires specialized marketing, as it requires defining or redefining the activity, developing or revising the offer, analyzing the competition, and understanding the new customer behavior. However, the results expected from such a policy remained insufficient and concluded that while desert tourism is meant to be a by-product of coastal tourism, coastal tourism still predominates in Tunisia. Saharan tourism is defined as a "desert" product, similar to thalassotherapy and golf. It serves as a way for guests who have travelled to the coast to extend their stay. Saharan tourism remained a complementary product (complementation to the sea through circuits towards the Sahara). This work aims to include how the Sahara and these regions can become fully-fledged tourist destinations.
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Diallo, Mame Yoro, Martina Čížková, Iva Kulichová, et al. "Circum-Saharan Prehistory through the Lens of mtDNA Diversity." Genes 13, no. 3 (2022): 533. http://dx.doi.org/10.3390/genes13030533.
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African history has been significantly influenced by the Sahara, which has represented a barrier for migrations of all living beings, including humans. Major exceptions were the gene flow events that took place between North African and sub-Saharan populations during the so-called African Humid Periods, especially in the Early Holocene (11.5 to 5.5 thousand years ago), and more recently in connection with trans-Saharan commercial routes. In this study, we describe mitochondrial DNA (mtDNA) diversity of human populations from both sides of the Sahara Desert, i.e., both from North Africa and the Sahel/Savannah belt. The final dataset of 7213 mtDNA sequences from 134 African populations encompasses 470 newly collected and 6743 previously published samples, which were analyzed using descriptive methods and Bayesian statistics. We completely sequenced 26 mtDNAs from sub-Saharan samples belonging to the Eurasian haplogroup N1. Analyses of these N1 mitogenomes revealed their possible routes to the Sahel, mostly via Bab el-Mandab. Our results indicate that maternal gene flow must have been important in this circum-Saharan space, not only within North Africa and the Sahel/Savannah belt but also between these two regions.
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Varrica, Daniela, and Maria Grazia Alaimo. "Influence of Saharan Dust on the Composition of Urban Aerosols in Palermo City (Italy)." Atmosphere 15, no. 3 (2024): 254. http://dx.doi.org/10.3390/atmos15030254.
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The Mediterranean Basin is involved in a recurring phenomenon wherein air masses laden with dust from North Africa impact the southern regions of the European continent. Saharan dust has been associated with increased mortality and respiratory symptoms. Palermo is a large coastal city, and in addition to the impact of desert dust particles, it has a mixture of anthropogenic sources of pollutants. In this study, we collected Saharan dust samples during August 2022 and October 2023, following a high-intensity Saharan dust event, and measured concentrations of 33 major and trace elements as well as Rare Earth Elements (REE). The mineralogical characterization of the deposition dust collected during Saharan events revealed calcite, dolomite, quartz, and clay minerals. The presence of palygorskite is indicative of Saharan events. Seven elements (Ca, Mg, Al, Ti, Fe, K, and Na) account for 98% of the total analyzed inorganic burden. Elemental ratios are valuable tools in atmospheric sciences for estimating sources of air masses. The results highlight that the city of Palermo is mainly affected by dust from the north-western Sahara.
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Barker, G. W. W. "ULVS XVI: Prehistoric Rock Carvings in the Tripolitanian Pre-desert." Libyan Studies 17 (1986): 69–86. http://dx.doi.org/10.1017/s0263718900007068.
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AbstractThis paper discusses three groups of rock art in their local, Tripolitanian, context and in terms of their wider relationship with the known corpus of Saharan prehistoric art. The rock carvings at Maia Dib, Udei el Chel/Caf el-Metchia and el-Tolga are described and some preliminary thoughts advanced as to their date and significance. Some suggestions are also made regarding the possible relationship between these carvings and the climatic and environmental changes which characterised the Sahara in later prehistory.
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Arnaiz-Villena, Antonio, Marcial Medina, Valentín Ruíz-del-Valle, et al. "The Saharo-Canarian Circle: The forgotten Prehistory of Euro African Atlantic façade and its lack of eastern demic diffusion evidences." International Journal of Modern Anthropology 2, no. 16 (2021): 586–600. http://dx.doi.org/10.4314/ijma.v2i16.4.
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Canarians, North Africans and Iberians show a close genetic relatedness. Greeks have a Sub-Saharan gene input according to HLA and other autosomic markers. Also, there is a genetic kinship between both Atlantic Euro Africans and North African/Arabic people. This is concordant with a drying humid Sahara Desert, which may have occurred about 6,000 years BC, and the subsequent northwards emigration of Saharan people may have also happened in Pharaonic times. This genetic input into Atlantic and Mediterranean Europe/Africa is also supported with Lineal Megalithic Scripts in Canary Islands (as well as in Iberia) together with simple Iberian semi-syllabary rock inscriptions both at Canary Islands and Ti-m Missaou (Algeria, Central southern Sahara). Lineal African/European scripts are found in certain languages scripts like Berber/Tuareg, Iberian, Runes, Etruscan, Bulgarian (Sitovo and Gradeshnitza, 6,000 years BP), Italian Old Scripts (Lepontic, Venetic, Raetic), Minoan Lineal A and Vinca scripts (Romania, Serbia, Greece, Bulgaria, about 4,000 years BP). The possibility that Megalithic Lineal Scripts have given rise to these languages lineal writing is feasible because admixture of languages rock scripts and Megalithic Lineal Scripts have been found. Thus, resistance of Canarian aborigines (Guanches) to Carthage, Rome and Arabs left a bulk of Canarian-Saharan information which is used to study both Saharan and Canarian Prehistory, and also Atlantic and Mediterranean beginning of European and other civilizations: this preserved prehistoric inheritance may be named the “Saharo-Canarian Circle” of prehistoric knowledge. Also, linguistics-epigraphy, physical anthropology, archaeology, and domesticated cattle shows a close North Africa-Iberia Mesolithic/Neolithic relationship and demonstrates that the demic diffusion model does not exist in Iberia. Also, Tassili Sahara paintings of domesticated cattle appear 1,000 years before those agricultural practices started at Middle East. Finally, it is also inferred that circum-Mediterranean contacts during thousand years between ice and desert constructed Mediterranean cultures from Canary Islands to Ancient Great Persia and this is the origin of Classical Mediterranean cultures that was later exclusively attributed to Rome and Greece.
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Chaouni, Aziza. "Desert Ecotourism: Investigating Ecolodges in the Sahara." Open House International 32, no. 4 (2007): 64–74. http://dx.doi.org/10.1108/ohi-04-2007-b0007.
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This paper attempts to delineate an adequate typology for desert ecolodges in the developing world by focusing on the Northern Saharan region as an area of study. To do so, it first situates ecotourism in the Sahara within the larger history of tourism in the region. Then, it studies its evolution and manifestations while concentrating on the challenges it is confronted to as well as the environmental impacts it inflicts, mainly due to the inadequacy of its accommodation facilities. Hence, the paper advances a new paradigm for desert ecolodges, stressing the importance of a comprehensive resource and waste management strategy. Other recommended features include sustainable building methods, community involvement, and nature conservation and education. Each one of these attributes is further analyzed in three successful case studies located in the Egyptian desert. The study of these cases reveal that in order to decrease their environmental footprint, desert ecolodges should put more efforts into integrating new energy and water harvesting technologies as well as establish a symbiotic relationship with the oasis landscape.
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Webb, James L. A. "The Horse and Slave Trade Between the Western Sahara and Senegambia." Journal of African History 34, no. 2 (1993): 221–46. http://dx.doi.org/10.1017/s0021853700033338.
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Following the late fifteenth- and sixteenth-century cavalry revolution in Senegambia, the horse and slave trade became a major sector of the desert-edge political economy. Black African states imported horses from North Africa and the western Sahara in exchange for slaves. Over time, under conditions of increasing aridity, the zone of desert horse-breeding was pushed south, and through crossbreeding with the small disease-resistant indigenous horses of the savanna, new breeds were created. Although the savanna remained an epidemiologically hostile environment for the larger and more desirable horses bred in North Africa, in the high desert and along the desert fringe, Black African states continued to import horses in exchange for slaves into the period of French colonial rule.The evidence assembled on the horse trade into northern Senegambia raises the difficult issue of the relative quantitative importance of the Atlantic and Saharan/North African slave trades and calls into question the assumption that the Atlantic slave trade was the larger of the two. Most available evidence concerns the Wolof kingdoms of Waalo and Kajoor. It suggests that the volume of slaves exported north into the desert from Waalo in the late seventeenth century was probably at least ten times as great as the volume of slaves exported into the Atlantic slave trade. For both Waalo and Kajoor, this ratio declined during the first half of the eighteenth century as slave exports into the Atlantic markets increased. The second half of the eighteenth century saw an increase in predatory raiding from the desert which produced an additional flow of north-bound slaves. For Waalo and Kajoor – and probably for the other Black African states of northern Senegambia – the flow of slaves north to Saharan and North African markets probably remained the larger of the two export volumes over the eighteenth century. This northward flow of slaves continued strong after the abolition of the Atlantic slave trade and was only shut down with the imposition of French colonial authority.
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Zakey, A. S., F. Solmon, and F. Giorgi. "Development and testing of a desert dust module in a regional climate model." Atmospheric Chemistry and Physics Discussions 6, no. 2 (2006): 1749–92. http://dx.doi.org/10.5194/acpd-6-1749-2006.
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Abstract. We develop a desert dust module and implement it within a regional climate model (RegCM). The dust module includes emission, transport, gravitational settling, wet and dry removal and calculations of dust optical properties. The coupled RegCM-dust model is applied to the simulation of two dust episodes over the Sahara region (a northeastern Africa dust outbreak, and a west Africa-Atlantic dust outbreak observed during the SHADE "Saharan Dust Experiment") as well as a three month simulation over an extended domain covering the Africa-Europe sector. Comparison with satellite and insitu (for SHADE) measurements shows that the model captures the main spatial (both horizontal and vertical) and temporal features of the dust distribution. The main model deficiency occurred in the SHADE case, when the model failed to accurately simulate the development of a mesoscale low associated with an easterly wave that contributed to the generation of the dust outbreak. The model appears suitable to conduct long term simulations of the effects of Saharan dust on African and European climate.
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Zakey, A. S., F. Solmon, and F. Giorgi. "Implementation and testing of a desert dust module in a regional climate model." Atmospheric Chemistry and Physics 6, no. 12 (2006): 4687–704. http://dx.doi.org/10.5194/acp-6-4687-2006.
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Abstract. In an effort to improve our understanding of aerosol impacts on climate, we implement a desert dust module within a regional climate model (RegCM). The dust module includes emission, transport, gravitational settling, wet and dry removal and calculations of dust optical properties. The coupled RegCM-dust model is used to simulate two dust episodes observed over the Sahara region (a northeastern Africa dust outbreak, and a west Africa-Atlantic dust outbreak observed during the SHADE "Saharan Dust Experiment"), as well as a three month simulation over an extended domain covering the Africa-Europe sector. Comparisons with satellite and local aerosol optical depth measurements shows that the model captures the main spatial (both horizontal and vertical) and temporal features of the dust distribution. The main model deficiency occurs in the representation of certain dynamical patterns observed during the SHADE case which is associated with an active easterly wave that contributed to the generation of the dust outbreak. The model appears suitable to conduct long term simulations of the effects of Saharan dust on African and European climate.
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Santos, D., M. J. Costa, A. M. Silva, and R. Salgado. "Modeling Saharan desert dust radiative effects on clouds." Atmospheric Research 127 (June 2013): 178–94. http://dx.doi.org/10.1016/j.atmosres.2012.09.024.
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García, O. E., A. M. Díaz, F. J. Expósito, J. P. Díaz, A. Redondas, and T. Sasaki. "Aerosol Radiative Forcing and Forcing Efficiency in the UVB for Regions Affected by Saharan and Asian Mineral Dust." Journal of the Atmospheric Sciences 66, no. 4 (2009): 1033–40. http://dx.doi.org/10.1175/2008jas2816.1.
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Abstract The influence of mineral dust on ultraviolet energy transfer is studied for two different mineralogical origins. The aerosol radiative forcing ΔF and the forcing efficiency at the surface ΔFeff in the range 290–325 nm were estimated in ground-based stations affected by the Saharan and Asian deserts during the dusty seasons. UVB solar measurements were taken from the World Ozone and Ultraviolet Data Center (WOUDC) for four Asian stations (2000–04) and from the Santa Cruz Observatory, Canary Islands (2002–03), under Gobi and Sahara Desert influences, respectively. The Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth at 550 nm was used to characterize the aerosol load τ, whereas the aerosol index provided by the Total Ozone Mapping Spectrometer (TOMS) sensor was employed to identify the mineral dust events. The ΔF is strongly affected by the aerosol load, the values found being comparable in both regions during the dusty seasons. Under those conditions, ΔF values as large as −1.29 ± 0.53 W m−2 (τ550 = 0.48 ± 0.24) and −1.43 ± 0.38 W m−2 (τ550 = 0.54 ± 0.26) were reached under Saharan and Asian dust conditions, respectively. Nevertheless, significant differences have been observed in the aerosol radiative forcing per unit of aerosol optical depth in the slant path, τS. The maximum ΔFeff values associated with dust influences were −1.55 ± 0.20 W m−2 τS550−1 for the Saharan region and −0.95 ± 0.11 W m−2 τS550−1 in the Asian area. These results may be used as a benchmark database for establishing aerosol corrections in UV satellite products or in global climate model estimations.
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Crouvi, Onn, Rivka Amit, Yehouda Enzel, Naomi Porat, and Amir Sandler. "Sand dunes as a major proximal dust source for late Pleistocene loess in the Negev Desert, Israel." Quaternary Research 70, no. 2 (2008): 275–82. http://dx.doi.org/10.1016/j.yqres.2008.04.011.
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AbstractGrain size analyses of three hilltop, primary eolian loess sequences in the Negev desert, southern Israel, show a bimodal grain-size distribution at 50–60 μm and 3–8 μm. Using analyses of mineralogy and OSL ages we demonstrate that the coarse mode is composed mostly of quartz grains and its relative magnitude increases regionally with time, suggesting an enhancement of a time-transgressive proximal dust source compared to a distal, Saharan fine-grain dust. The only proximal dust source for large amount of coarse silt quartz grains is the sands that advanced into Sinai and the Negev concurrently with the loess accretion during the late Pleistocene as a result of the exposure of the Mediterranean shelf. We therefore propose that the coarse silt quartz grains were formed through eolian abrasion within the margins of an advancing sand sea. This relationship between desert sand seas as a source for proximal coarse dust and desert margin loess deposits can be applicable to other worldwide deserts such as Northern Africa, China and Australia.
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Doganay, H., D. Akcali, T. Goktaş, et al. "African Dust-Laden Atmospheric Conditions Activate the Trigeminovascular System." Cephalalgia 29, no. 10 (2009): 1059–68. http://dx.doi.org/10.1111/j.1468-2982.2008.01839.x.
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It has been recently noticed that dust originating from deserts can be transported to other continents by the atmosphere and has an adverse effect on public health, such as increased asthma attacks. Dust originating from the Saharan Desert could initiate a series of reactions upon contact with cloud water and results in the formation of reduced iron (Fe2+), oxalate and various basic amino acids. We aimed to evaluate whether the simulation of Saharan dust-containing atmospheric conditions could trigger the trigeminovascular system. Freely moving rats incubated within simulated atmospheric conditions containing (i) Saharan dust, (ii) Co60 gamma ray-treated Saharan dust (sterilized) and (iii) dust-free air, were investigated for the presence of c-fos expression in trigeminal nucleus caudalis (TNC) and for NOx (nitrate+nitrite) levels in blood samples. Atmospheric samples were analysed for microorganisms. Saharan dust-containing atmospheric conditions induced c-fos expression in nociceptive neurons within TNC. The number of c-fos+ neurons in superficial lamina of TNC was significantly higher in the Saharan dust group (32.9 ± 5.3, P = 0.0001) compared with dust-free air (11.02 ± 2.7) or Co60-treated Saharan dust groups (15.01 ± 2.4). An increase in NOx levels was detected in blood samples of rats exposed to Saharan dust-containing atmosphere. This study has revealed an unknown environmental factor as a possible trigger for headache. It is the first time that transport of Saharan dust with the atmospheric air stream has been documented to be able to trigger the trigeminovascular system in animals. Further studies are needed to explore the mechanisms and molecules that mediate the nociceptive effect and to guide new treatment strategies.
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Boose, Yvonne, Philipp Baloh, Michael Plötze, et al. "Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 2: Deposition nucleation and condensation freezing." Atmospheric Chemistry and Physics 19, no. 2 (2019): 1059–76. http://dx.doi.org/10.5194/acp-19-1059-2019.
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Abstract. Mineral dust particles from deserts are amongst the most common ice nucleating particles in the atmosphere. The mineralogy of desert dust differs depending on the source region and can further fractionate during the dust emission processes. Mineralogy to a large extent explains the ice nucleation behavior of desert aerosol, but not entirely. Apart from pure mineral dust, desert aerosol particles often exhibit a coating or are mixed with small amounts of biological material. Aging on the ground or during atmospheric transport can deactivate nucleation sites, thus strong ice nucleating minerals may not exhibit their full potential. In the partner paper of this work, it was shown that mineralogy determines most but not all of the ice nucleation behavior in the immersion mode found for desert dust. In this study, the influence of semi-volatile organic compounds and the presence of crystal water on the ice nucleation behavior of desert aerosol is investigated. This work focuses on the deposition and condensation ice nucleation modes at temperatures between 238 and 242 K of 18 dust samples sourced from nine deserts worldwide. Chemical imaging of the particles' surface is used to determine the cause of the observed differences in ice nucleation. It is found that, while the ice nucleation ability of the majority of the dust samples is dominated by their quartz and feldspar content, in one carbonaceous sample it is mostly caused by organic matter, potentially cellulose and/or proteins. In contrast, the ice nucleation ability of an airborne Saharan sample is found to be diminished, likely by semi-volatile species covering ice nucleation active sites of the minerals. This study shows that in addition to mineralogy, other factors such as organics and crystal water content can alter the ice nucleation behavior of desert aerosol during atmospheric transport in various ways.
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Egeter, Bastian, Sara Peixoto, José C. Brito, Simon Jarman, Pamela Puppo, and Guillermo Velo-Antón. "Challenges for assessing vertebrate diversity in turbid Saharan water-bodies using environmental DNA." Genome 61, no. 11 (2018): 807–14. http://dx.doi.org/10.1139/gen-2018-0071.
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The Sahara desert is the largest warm desert in the world and a poorly explored area. Small water-bodies occur across the desert and are crucial habitats for vertebrate biodiversity. Environmental DNA (eDNA) is a powerful tool for species detection and is being increasingly used to conduct biodiversity assessments. However, there are a number of difficulties with sampling eDNA from such turbid water-bodies and it is often not feasible to rely on electrical tools in remote desert environments. We trialled a manually powered filtering method in Mauritania, using pre-filtration to circumvent problems posed by turbid water in remote arid areas. From nine vertebrate species expected in the water-bodies, four were detected visually, two via metabarcoding, and one via both methods. Difficulties filtering turbid water led to severe constraints, limiting the sampling protocol to only one sampling point per study site, which alone may largely explain why many of the expected vertebrate species were not detected. The amplification of human DNA using general vertebrate primers is also likely to have contributed to the low number of taxa identified. Here we highlight a number of challenges that need to be overcome to successfully conduct metabarcoding eDNA studies for vertebrates in desert environments in Africa.
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Bunbury, Judith, Piers Litherland, Jenny Litherland, et al. "Climate resilience in the desert areas of Egypt." Claroscuro. Revista del Centro de Estudios sobre Diversidad Cultural, no. 22 (May 22, 2024): 1–19. http://dx.doi.org/10.35305/cl.vi22.135.
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Today the Saharan region is known as a hyper-arid environment with minimal human activity outside the few oases. However, archaeological evidence suggests that, in the past, the landscape was more accessible and that settlements sprang up around springs and wells that were linked by well-used routes. Our studies suggest that this activity was concentrated into historical periods when fresh water was available, particularly the Eighteenth Dynasty of the New Kingdom and the Graeco-Roman Period. Comparison with records of global temperature proxies in the Greenland Ice Sheet Project show that these periods of activity were also times of high global temperatures, leading to the conclusion times of global warming produce increased rainfall in the Saharan region that supports ecosystems and activity in the desert.
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Guirado, C., E. Cuevas, V. E. Cachorro, et al. "Aerosol characterization at the Saharan AERONET site Tamanrasset." Atmospheric Chemistry and Physics Discussions 14, no. 11 (2014): 16641–90. http://dx.doi.org/10.5194/acpd-14-16641-2014.
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Abstract. More than two years of columnar atmospheric aerosol measurements (2006–2009) at Tamanrasset site, in the heart of the Sahara desert, are analysed. AERONET level 2.0 data were used. The KCICLO method was applied to a part of level 1.5 data series to improve the quality of the results. The annual variability of aerosol optical depth (AOD) and Angstrom exponent (AE) has been found to be strongly linked to the Convective Boundary Layer (CBL) thermodynamic features. The dry-cool season (autumn and winter time) is characterized by a shallow CBL and very low mean turbidity (AOD ~ 0.09 at 440 nm, AE ~ 0.62). The wet-hot season (spring and summer time) is dominated by high turbidity of coarse dust particles (AE ~ 0.28, AOD ~ 0.39 at 440 nm) and a deep CBL. The aerosol-type characterization shows desert mineral dust as prevailing aerosol. Both pure Saharan dust and very clear sky conditions are observed depending on the season. However, several case studies indicate an anthropogenic fine mode contribution from Libya and Algeria's industrial areas. The Concentration Weighted Trajectory (CWT) source apportionment method was used to identify potential sources of air masses arriving at Tamanrasset at several heights for each season. Microphysical and optical properties and precipitable water vapour were also investigated.
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Rizzolo, Joana A., Cybelli G. G. Barbosa, Guilherme C. Borillo, et al. "Soluble iron nutrients in Saharan dust over the central Amazon rainforest." Atmospheric Chemistry and Physics 17, no. 4 (2017): 2673–87. http://dx.doi.org/10.5194/acp-17-2673-2017.
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Abstract. The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m−3), Fe(II) (16 ng m−3), Na (470 ng m−3), Ca (194 ng m−3), K (65 ng m−3), and Mg (89 ng m−3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the main source of soluble mineral nutrients.
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Urrutia-Pereira, Marilyn, Luciana Varanda Rizzo, Patrícia Latour Staffeld, Herberto Jose Chong-Neto, Giovanni Viegi, and Dirceu Solé. "Dust from the Sahara to the American Continent: Health impacts." Allergologia et Immunopathologia 49, no. 4 (2021): 187–94. http://dx.doi.org/10.15586/aei.v49i4.436.
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The Saharan Air Layer is a mass of hot, dry air laden with dust that forms over the Sahara and moves towards the Atlantic Ocean. This air mass contains soil dust particles emitted by the action of winds on the African continent. Between June and August, the large-scale patterns of wind circulation transport dust from the Sahara across the tropical North Atlantic Ocean,affecting parts of the Caribbean, Central America, Mexico, even some regions of the United States, and the Mediterranean and Southern Europe. Between December and April, wind circulation patterns facilitate dust transportation from the Sahara to the northern parts of South America and the Amazon. This dust transportation a phenomenon of interest to geosciencesand public health because of the potential health impacts of dust dispersion and circulation in the atmosphere. Thus, we assessed the relationship between exposure to Saharan dust (SahD) and its implications for human health in the Americas. We performed a nonsystematic review in the PubMed, Google Scholar, EMBASE, and Scielo databases of studies published between 2000 and 2020 in Portuguese, English, French, or Spanish using the search words “Saharan dust,” or “mineral dust,” or “desert dust,” and “human health.” The available direct air pollutants measurements indicate that the pollution level in the cities affected on a constant and prolonged basis is high versus acceptable standards. Further, this review also showed that the negative health effects of SahD are sparsely studied in the Americas.
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Montero-Calasanz, Maria del Carmen, Markus Göker, Gabriele Pötter, et al. "Geodermatophilus normandii sp. nov., isolated from Saharan desert sand." International Journal of Systematic and Evolutionary Microbiology 63, Pt_9 (2013): 3437–43. http://dx.doi.org/10.1099/ijs.0.051201-0.
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A novel Gram-reaction-positive actinobacterial strain, designated CF5/3T, was isolated from a sand sample obtained in the Sahara Desert, Chad. The greenish-black-pigmented isolate was aerobic and exhibited optimal growth from 25–40 °C at pH 6.0–10.0 with 0–1 % (w/v) NaCl. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus . The DNA G+C content of the genome of the novel strain was 75.5 mol%. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diamino acid. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and a minor fraction of phosphatidylglycerol. MK-9(H4) was the dominant menaquinone, and galactose was detected as a diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids: iso-C15 : 0 and iso-C16 : 0. Analysis of 16S rRNA gene sequences showed 95.6–98.8 % pairwise sequence identity with the members of the genus Geodermatophilus . Based on phenotypic and chemotaxonomic properties, as well as phylogenetic distinctiveness, the isolate represents a novel species, Geodermatophilus normandii, with the type strain CF5/3T ( = DSM 45417T = CCUG 62814T = MTCC 11412T).
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Yaalon, Dan H. "Saharan dust and desert loess: effect on surrounding soils." Journal of African Earth Sciences (1983) 6, no. 4 (1987): 569–71. http://dx.doi.org/10.1016/0899-5362(87)90096-0.
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Vodounou, Victor A. "Development of Special Education in Selected Sub-Saharan African Countries." Rural Special Education Quarterly 15, no. 3 (1996): 38–41. http://dx.doi.org/10.1177/875687059601500307.
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African countries South of the Saharan Desert are predominately rural. A review of literature on current trends in special education in selected Sub-Saharan African countries indicates a changing attitude toward individuals with disabilities. Modern practices have been influenced by the development of basic education, the enactment of national policies, and heightened public awareness created by the United Nations' International Year (1981) and Decade of the Disabled (1981–1991). This work provides an overview of the historical development of special education in several Sub-Saharan countries, describes current conditions, and makes recommendations for further positive change.
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Chatzikonstantinou, N., T. J. Mertzimekis, A. Godelitsas, et al. "Using synchrotron radiation to study iron phases in Saharan dust samples from Athens skies." HNPS Proceedings 21 (March 8, 2019): 136. http://dx.doi.org/10.12681/hnps.2018.
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The Sahara desert is the largest source of dust in the world. Saharan dust is characterized by great com- plexity, composed mainly of mixtures of mineral phases (amorphous or crystalline, with particle sizes of the order of μm or even nm). The presence of amorphous components makes it difficult to detect their struc- ture. For this purpose the spectroscopic technique of X–ray absorption fine structure μ–XAFS combined to ultrabright synchrotron SR microbeams is suitable. SR’s main advantage is the recording of spectra in a very short time. In this paper we focus on the study of forms of iron deposited on southeast Mediterranean Sea and mainland of Greece by the waves of Saharan dust. Data collection was carried out at the premises of ANKA (KIT, Germany) on the beamline SUL–X of the environmental research laboratory with advanced X–ray spectroscopic techniques, μ–XRF, μ–XRD and μ–XAFS. Results from the measurements and the simulated spectrum are presented.
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Arnaiz-Villena, Antonio, Valentín Ruiz-del-Valle, Adrián López-Nares, and Fabio Suárez-Trujillo. "Iberian inscriptions in Sahara Desert rocks (Ti-m Missaou, Ahaggar Mts. area, Algeria): first evidence of incise Iberian rock scripts in continental North Africa." International Journal of Modern Anthropology 15, no. 2 (2021): 440–67. http://dx.doi.org/10.4314/ijma.v15i2.3.
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In the present paper, we show Iberian or Iberian-Guanche scripts found in the Middle of Sahara Desert, Ti-m Missaou (Tim Missao, Tim Missaw), 270 km SouthWest of Tamanrasset on Ahaggar or Hoggar Mountains (Mts.) area (Algeria). More Iberian scripts may be earthed beneath Sahara Desert sands or have been neglected by observers. We also put forward that Iberian semi-syllabary may have its origin in the Neolithic Saharo-Canarian Circle, the same as other Mediterranean, Atlantic and European lineal scripts (apart from Berber/Tuareg) like Etruscan, Runes, Old Italian languages, Minoan Lineal A, Sitovo and Gradeshnitsa (Bulgaria) writings (6,000 yearsBC) and others. In fact, Strabo wrote that Iberians had written language before since 6,000 BC. On the other hand, Sahara Desert was green and populated since before 5,000 years BC and we had proposed that most of Mediterranean culture, languages and writing, had a Saharan origin. Ti-m Missaou Sahara Iberian inscriptions, together with our previous and others researches on Canary Islands, further support this proposal, i.e.: rock scripts, Gimbutas-like Paleolithic figurines and unusual artifacts, like a lunisolar Egyptian-like calendar (“Cheeseboard/Quesera” at Lanzarote) carved in a Megalithic stone, do no support that Phoenicians and Romans carried Canarian ancient Guanche culture. Finally, a continuous lineal writing systems developing seems to have occurred during Paleolithic and Neolithic Epochs, which also harbor the related incise Lineal Megalithic Scripts that could have given rise to Iberian development and other lineal African, European and Mediterranean lineal language scripts. Our present new data is interpreted in the context of the Sahara people migration which occurred when hyperarid conditions started establishing about 6,000 years BC.
 Keywords: Iberian, Iberian-Guanche, Scripts, Canary Islands, Lanzarote, Fuerteventura, Prehistory, Saharo-Canarian Circle, Genetics, Megaliths, Iberia, Sahara, Atlantic, Mediterranean, Lineal Scripts, Neolithic, Tamanrasset, Hoggar, Ahaggar, Usko-Mediterranean,Etruscan, Tuareg, Berber, Lineal A.
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Arnaiz-Villena, Antonio, Valentín Ruiz-del-Valle, Adrián López-Nares, and Fabio Suárez-Trujillo. "Iberian inscriptions in Sahara Desert rocks (Ti-m Missaou, Ahaggar Mts. area, Algeria): first evidence of incise Iberian rock scripts in continental North Africa." International Journal of Modern Anthropology 2, no. 15 (2021): 440–67. http://dx.doi.org/10.4314/ijma.v2i15.3.
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In the present paper, we show Iberian or Iberian-Guanche scripts found in the Middle of Sahara Desert, Ti-m Missaou (Tim Missao, Tim Missaw), 270 km SouthWest of Tamanrasset on Ahaggar or Hoggar Mountains (Mts.) area (Algeria). More Iberian scripts may be earthed beneath Sahara Desert sands or have been neglected by observers. We also put forward that Iberian semi-syllabary may have its origin in the Neolithic Saharo-Canarian Circle, the same as other Mediterranean, Atlantic and European lineal scripts (apart from Berber/Tuareg) like Etruscan, Runes, Old Italian languages, Minoan Lineal A, Sitovo and Gradeshnitsa (Bulgaria) writings (6,000 yearsBC) and others. In fact, Strabo wrote that Iberians had written language before since 6,000 BC. On the other hand, Sahara Desert was green and populated since before 5,000 years BC and we had proposed that most of Mediterranean culture, languages and writing, had a Saharan origin. Ti-m Missaou Sahara Iberian inscriptions, together with our previous and others researches on Canary Islands, further support this proposal, i.e.: rock scripts, Gimbutas-like Paleolithic figurines and unusual artifacts, like a lunisolar Egyptian-like calendar (“Cheeseboard/Quesera” at Lanzarote) carved in a Megalithic stone, do no support that Phoenicians and Romans carried Canarian ancient Guanche culture. Finally, a continuous lineal writing systems developing seems to have occurred during Paleolithic and Neolithic Epochs, which also harbor the related incise Lineal Megalithic Scripts that could have given rise to Iberian development and other lineal African, European and Mediterranean lineal language scripts. Our present new data is interpreted in the context of the Sahara people migration which occurred when hyperarid conditions started establishing about 6,000 years BC.
 Keywords: Iberian, Iberian-Guanche, Scripts, Canary Islands, Lanzarote, Fuerteventura, Prehistory, Saharo-Canarian Circle, Genetics, Megaliths, Iberia, Sahara, Atlantic, Mediterranean, Lineal Scripts, Neolithic, Tamanrasset, Hoggar, Ahaggar, Usko-Mediterranean,Etruscan, Tuareg, Berber, Lineal A.
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Mitsakou, C., G. Kallos, N. Papantoniou, et al. "Saharan dust levels in Greece and received inhalation doses." Atmospheric Chemistry and Physics Discussions 8, no. 3 (2008): 11967–96. http://dx.doi.org/10.5194/acpd-8-11967-2008.
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Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.
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Boose, Yvonne, Berko Sierau, M. Isabel García, et al. "Ice nucleating particles in the Saharan Air Layer." Atmospheric Chemistry and Physics 16, no. 14 (2016): 9067–87. http://dx.doi.org/10.5194/acp-16-9067-2016.
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Abstract. This study aims at quantifying the ice nucleation properties of desert dust in the Saharan Air Layer (SAL), the warm, dry and dust-laden layer that expands from North Africa to the Americas. By measuring close to the dust's emission source, before aging processes during the transatlantic advection potentially modify the dust properties, the study fills a gap between in situ measurements of dust ice nucleating particles (INPs) far away from the Sahara and laboratory studies of ground-collected soil. Two months of online INP concentration measurements are presented, which were part of the two CALIMA campaigns at the Izaña observatory in Tenerife, Spain (2373 m a.s.l.), in the summers of 2013 and 2014. INP concentrations were measured in the deposition and condensation mode at temperatures between 233 and 253 K with the Portable Ice Nucleation Chamber (PINC). Additional aerosol information such as bulk chemical composition, concentration of fluorescent biological particles as well as the particle size distribution was used to investigate observed variations in the INP concentration. The concentration of INPs was found to range between 0.2 std L−1 in the deposition mode and up to 2500 std L−1 in the condensation mode at 240 K. It correlates well with the abundance of aluminum, iron, magnesium and manganese (R: 0.43–0.67) and less with that of calcium, sodium or carbonate. These observations are consistent with earlier results from laboratory studies which showed a higher ice nucleation efficiency of certain feldspar and clay minerals compared to other types of mineral dust. We find that an increase of ammonium sulfate, linked to anthropogenic emissions in upwind distant anthropogenic sources, mixed with the desert dust has a small positive effect on the condensation mode INP per dust mass ratio but no effect on the deposition mode INP. Furthermore, the relative abundance of biological particles was found to be significantly higher in INPs compared to the ambient aerosol. Overall, this suggests that atmospheric aging processes in the SAL can lead to an increase in ice nucleation ability of mineral dust from the Sahara. INP concentrations predicted with two common parameterization schemes, which were derived mostly from atmospheric measurements far away from the Sahara but influenced by Asian and Saharan dust, were found to be higher based on the aerosol load than we observed in the SAL, further suggesting aging effects of INPs in the SAL.
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Menéndez, Inmaculada, José Mangas, Esperança Tauler, et al. "Aeolian influx and related environmental conditions on Gran Canaria during the early Pleistocene." Quaternary Research 91, no. 1 (2018): 35–50. http://dx.doi.org/10.1017/qua.2018.64.
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AbstractThe island of Gran Canaria is regularly affected by dust falls due to its proximity to the Saharan desert. Climatic oscillations may affect the Saharan dust input to the island. Geochemical, mineralogical, and textural analysis was performed on a well-developed and representative early Pleistocene paleosol to examine Saharan dust contribution to Gran Canaria. Significant and variable Saharan dust content was identified in addition to weathering products such as iron oxides and clay minerals. Variations in quartz and iron oxide concentrations in the paleosol likely reflect different Saharan dust input in more/less-contrasted rhexistasic/biostatic climatic conditions. Linking the quartz content in Canarian soils, the Ingenio paleosol, and two Canarian loess-like deposits to different ages from the Quaternary, we hypothesized that the dust input should be lower (about 33–38%) throughout the early to middle Pleistocene than during the late Quaternary. The Saharan dust input to the Gran Canaria profile in the Pleistocene persisted in spite of climatic variations.
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Rodriguez-Navarro, Carlos, Fulvio di Lorenzo, and Kerstin Elert. "Mineralogy and physicochemical features of Saharan dust wet deposited in the Iberian Peninsula during an extreme red rain event." Atmospheric Chemistry and Physics 18, no. 13 (2018): 10089–122. http://dx.doi.org/10.5194/acp-18-10089-2018.
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Abstract. The mineralogy and physicochemical features of Saharan dust particles help to identify source areas and determine their biogeochemical, radiative, and health effects, but their characterization is challenging. Using a multianalytical approach, here we characterized with unprecedented level of detail the mineralogy and physicochemical properties of Saharan dust particles massively wet deposited ( ∼ 18 g m−2) following an extreme red rain event triggered by a northern African cyclone that affected the southern Iberian Peninsula during 21–23 February 2017. Abundant palygorskite and illite, and relatively high carbonate contents, well-known northern and north-western Saharan dust indicators, along with low chlorite content and significant amounts of smectites and kaolinite, whose abundance increases southwards in the western Sahara, complemented by satellite imagery and back/forward trajectories, show that the most probable dust source areas were (i) southern/central Algeria, northern Mali, and northwestern Niger, and (ii) northern Algeria, southern Tunisia, and northwestern Libya. Scanning and transmission electron microscopy analyses, including Z-contrast high angle annular dark field (HAADF) imaging and analytical electron microscopy (AEM), show that clay minerals include abundant structural Fe (55 % of the total Fe) and typically form nanogranular aggregates covered or interspersed with amorphous/poorly crystalline iron oxyhydroxide nanoparticles (ferrihydrite), which account for ∼ 18 % of the free Fe, the rest being goethite and hematite. These nanogranular aggregates tend to form rims lining large silicate and carbonate particles. Such internally mixed iron-containing phases are the main contributors to the observed absorption of solar and thermal radiation, and along with the abundant coarse/giant particles ( > 10 µm) strongly affect the dust direct radiative forcing. The lack of secondary sulfates in aggregates of unaltered calcite internally mixed with clays/iron-rich nanoparticles shows that iron-rich nanoparticles did not form via atmospheric (acid) processing but were already present in the dust source soils. Such iron-rich nanoparticles, in addition to iron-containing clay (nano)particles, are the source of the ∼ 20 % soluble (bioavailable) iron in the studied desert dust. The dust particles are a potential health hazard, specifically the abundant and potentially carcinogenic iron-containing palygorskite fibers. Ultimately, we show that different source areas are activated over large desert extensions, and large quantities of complex dust mixtures are transported thousands of kilometers and wet-deposited during such extreme events, which dwarf any other Saharan dust event affecting southwestern Europe. The past, present, and future trends, as well as impacts, of such extreme events must be taken into account when evaluating and modeling the manifold effects of the desert dust cycle.
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Field, P. R., O. Möhler, P. Connolly, et al. "Some ice nucleation characteristics of Asian and Saharan desert dust." Atmospheric Chemistry and Physics Discussions 6, no. 1 (2006): 1509–37. http://dx.doi.org/10.5194/acpd-6-1509-2006.
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Abstract. The large (7 m×4 m cylinder) AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber facility at Forschungszentrum, Karlsruhe, Germany was used to test the ice nucleating ability of two desert dust samples from the Sahara and Asia. At temperatures warmer than −40°C droplets were formed before ice crystals formed, there was no deposition nucleation observed. At temperatures colder than −40°C both dust samples exhibited dual nucleation events that were observed during the same expansion experiment. The primary nucleation event occurred at ice saturation ratios of 1.1 to 1.3 and is likely to be a deposition nucleation mode. The secondary nucleation event occurred at ice saturation ratios between 1.35 and 1.5. It is unclear whether this ice nucleation event is via a further deposition mode or a condensation mode. The activated fractions of desert dust ranged from ~5–10% at −20°C to 20–40% at temperatures colder than −40°C. There was no obvious difference between the nucleation behaviour of the two dust samples.
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Arnaiz-Villena, Antonio, Ignacio Juarez, José Palacio-Grüber, Adrián Lopez-Nares, and Fabio Suarez-Trujillo. "The Northern Migrations from a drying Sahara (6,000 years BP): cultural and genetic influence in Greeks, Iberians and other Mediterraneans." International Journal of Modern Anthropology 15, no. 2 (2021): 484–507. http://dx.doi.org/10.4314/ijma.v15i2.5.
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Greeks have a Sub-Saharan gene input according to HLA and other autosomic markers. Iberians, Canarians, and North Africans show a close genetic relatedness. This is concordant with a drying humid Sahara Desert, which may have occurred about 6,000 years BC, and the subsequent northwards emigration of Saharan people may have also happened in Pharaonic times. Present study confirms this African gene input in Greeks according to 12th HLA International Workshop data, which was studied some years before by us. This genetic input into Atlantic and Mediterranean Europe/Africa is also supported with Lineal Megalithic Scripts in Canary Islands (as well as in Iberia) together with simple Iberian semi-syllabary rock inscriptions both at Canary Islands and Ti-m Missaou (Algeria, Central southern Sahara). Lineal African/European scripts are found in some language scripts like Berber/Tuareg, Iberian, Runes, Etruscan, Bulgarian (Sitovo and Gradeshnitza, 6,000 years BP), Italian Old Scripts (Lepontic, Venetic, Raetic), Minoan Lineal A, and other Aegean scripts. The possibility that Megalithic Lineal Scripts have given rise to these languages lineal writing is feasible because admixture of languages rock scripts and Megalithic Lineal Scripts may be found. Thus, resistance of Canarian aborigines (Guanches) to Cartago, Rome and Arabs left a bulk of Canarian-Saharan information which is used to study both Saharan and Canarian Prehistory, and also Atlantic and Mediterranean beginning of European and other civilizations: this preserved prehistoric inheritance may be named the “Saharo-Canarian Circle” of prehistoric knowledge. Also, linguisticsepigraphy, physical anthropology ,archaeology and domesticated cattle shows a close North Africa-Iberia Mesolithic/Neolithic relationship and demonstrates that the demic diffusion model does not exist in Iberia. Also, Tassili Sahara paintings of domesticated cattle appear 1,000 years before that agricultural practices started at Middle East.
 Keywords: Greeks, Macedonians, Sahara, Africa, Iberia, HLA, Genetics, Spaniards, Portuguese, Berbers, Algerians, demic, diffusion, Canary Islands, Lanzarote, Malta, Cart-ruts, Quesera, Cheesboard, Iberian, language, Guanche, Usko-Mediterranean, Phoenicians
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Arnaiz-Villena, Antonio, Ignacio Juarez, José Palacio-Grüber, Adrián Lopez-Nares, and Fabio Suarez-Trujillo. "The Northern Migrations from a drying Sahara (6,000 years BP): cultural and genetic influence in Greeks, Iberians and other Mediterraneans." International Journal of Modern Anthropology 2, no. 15 (2021): 484–507. http://dx.doi.org/10.4314/ijma.v2i15.5.
Full textAbstract:
Greeks have a Sub-Saharan gene input according to HLA and other autosomic markers. Iberians, Canarians, and North Africans show a close genetic relatedness. This is concordant with a drying humid Sahara Desert, which may have occurred about 6,000 years BC, and the subsequent northwards emigration of Saharan people may have also happened in Pharaonic times. Present study confirms this African gene input in Greeks according to 12th HLA International Workshop data, which was studied some years before by us. This genetic input into Atlantic and Mediterranean Europe/Africa is also supported with Lineal Megalithic Scripts in Canary Islands (as well as in Iberia) together with simple Iberian semi-syllabary rock inscriptions both at Canary Islands and Ti-m Missaou (Algeria, Central southern Sahara). Lineal African/European scripts are found in some language scripts like Berber/Tuareg, Iberian, Runes, Etruscan, Bulgarian (Sitovo and Gradeshnitza, 6,000 years BP), Italian Old Scripts (Lepontic, Venetic, Raetic), Minoan Lineal A, and other Aegean scripts. The possibility that Megalithic Lineal Scripts have given rise to these languages lineal writing is feasible because admixture of languages rock scripts and Megalithic Lineal Scripts may be found. Thus, resistance of Canarian aborigines (Guanches) to Cartago, Rome and Arabs left a bulk of Canarian-Saharan information which is used to study both Saharan and Canarian Prehistory, and also Atlantic and Mediterranean beginning of European and other civilizations: this preserved prehistoric inheritance may be named the “Saharo-Canarian Circle” of prehistoric knowledge. Also, linguisticsepigraphy, physical anthropology ,archaeology and domesticated cattle shows a close North Africa-Iberia Mesolithic/Neolithic relationship and demonstrates that the demic diffusion model does not exist in Iberia. Also, Tassili Sahara paintings of domesticated cattle appear 1,000 years before that agricultural practices started at Middle East.
 Keywords: Greeks, Macedonians, Sahara, Africa, Iberia, HLA, Genetics, Spaniards, Portuguese, Berbers, Algerians, demic, diffusion, Canary Islands, Lanzarote, Malta, Cart-ruts, Quesera, Cheesboard, Iberian, language, Guanche, Usko-Mediterranean, Phoenicians
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Sherzad, Mohammed Fareed, and Dirk Goossens. "Wind Tunnel Experiments and Field Observations of Aeolian Sand Encroachment around Vernacular Settlements in the Saharan and Arabian Deserts." Buildings 12, no. 11 (2022): 2006. http://dx.doi.org/10.3390/buildings12112006.
Full textAbstract:
One of the key repercussions of the desertification process in the Sahara and the Arabian desert is increased aeolian sand drift and sand deposition. Despite its isolated location and severe desert climate—particularly in terms of solar radiation, sand drift, and sand deposition—the region of El-Oued Souf in the Grand Erg Oriental in the Algerian Sahara has been a key cultural and trade center for many centuries. To resist the extreme weather conditions, the architecture of the vernacular settlements in the region of El-Oued Souf has unique design traits. Newly constructed buildings, on the other hand, frequently employ technologies based on models imported or imposed from climates that bear little resemblance to the desert. As a result, the inhabitants of these structures live more ‘in the desert’ than ‘with the desert’. This study investigates the impact and the effectiveness of vernacular desert architecture to resist aeolian sand encroachment problems in sandy desert areas. The sand accumulation patterns around vernacular buildings were identified and quantified using wind tunnel experiments. The size and shape of the buildings, as well as their geometric configuration within the settlement, were investigated in relation to the shape and dimension of sand accumulation formations. Field observations in north Algeria and the United Arab Emirates confirmed the accumulation patterns produced by the wind tunnel experiments. The study proposes possible design indicators for building forms to minimize the impact of sand deposition on such forms.
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Qor-El-Aine, Achraf, András Béres, and Gábor Géczi. "Case Study of the Saharan Dust Effects on PM10 and PM2.5 Concentrations in Budapest in March 2022." Journal of Central European Green Innovation 10, Suppl 1 (2022): 67–78. http://dx.doi.org/10.33038/jcegi.3500.
Full textAbstract:
The Earth's climatic system is greatly dependent on atmospheric mineral dust. Dust particles are regarded as one of the less well-known contributors to recent climatic changes, much like other aerosol constituents. Fifty to seventy percent of the world's budget for mineral dust comes from the Sahara Desert areas. These sources can produce dust-loaded air masses that can travel great distances and affect many parts of the world including Europe, the Middle East, North and South America. In March 2022 Europe faced two Saharan Dust storms (14-19 and 28-31), that affected many countries including Hungary. We used registered measurements of PM10 and PM2.5 concentrations from urban background air quality station in Budapest and MONARCH model to assess the effects of the two Saharan Dust storms on Budapest. As measured by daily average concentrations, PM10 and PM2.5 concentrations rose by 12 µg/m3 and 10 µg/m3 respectively during the first Saharan Dust event (SDE1), and by 14 µg/m3 and 5 µg/m3 during the Second Saharan Dust event (SDE2). While the effects of both SDEs on PM10 were nearly identical, SDE1 had a greater impact on PM2.5 concentrations than SDE2. Moreover, the dust load arriving to Budapest as estimated by the MONARCH model was higher in the SDE1 (1.26 g/m3), and that was associated with high values of dust surface concentration and Dust optical depth (243.1 µg/m3 and 0.71).
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Mitsakou, C., G. Kallos, N. Papantoniou, et al. "Saharan dust levels in Greece and received inhalation doses." Atmospheric Chemistry and Physics 8, no. 23 (2008): 7181–92. http://dx.doi.org/10.5194/acp-8-7181-2008.
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Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in the south European Region and especially in urban areas, where there is also significant contribution from anthropogenic sources. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.
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Field, P. R., O. Möhler, P. Connolly, et al. "Some ice nucleation characteristics of Asian and Saharan desert dust." Atmospheric Chemistry and Physics 6, no. 10 (2006): 2991–3006. http://dx.doi.org/10.5194/acp-6-2991-2006.
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Abstract. The large (7 m×4 m cylinder, 84 m3) AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber facility at Forschungszentrum, Karlsruhe, Germany was used to test the ice nucleating ability of two desert dust samples from the Sahara and Asia. Aerosol samples were lognormally distributed with a mode diameter of 0.4(±0.1) μm and geometric standard deviation of ~1.7(±0.2). At temperatures warmer than −40°C droplets were formed before ice crystals formed and there was generally no deposition nucleation observed. At temperatures colder than −40°C both dust samples exhibited dual nucleation events that were observed during the same expansion experiment. The primary nucleation event occurred at ice saturation ratios of 1.1 to 1.3 and is likely to be a deposition nucleation mode. The secondary nucleation event occurred at ice saturation ratios between 1.35 and 1.5. We cannot categorically determine whether this ice nucleation event is via a further deposition mode or a condensation mode, but the presence of some soluble material in the dust samples leads us to favour the latter process. The activated fractions of desert dust ranged from ~5–10% at −20°C to 20–40% at temperatures colder than −40°C. There was no obvious difference between the nucleation behaviour of the two dust samples.
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Åkesson, Susanne, Giuseppe Bianco, and Anders Hedenström. "Negotiating an ecological barrier: crossing the Sahara in relation to winds by common swifts." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1704 (2016): 20150393. http://dx.doi.org/10.1098/rstb.2015.0393.
Full textAbstract:
The Sahara Desert is one of the largest land-based barriers on the Earth, crossed twice each year by billions of birds on migration. Here we investigate how common swifts migrating between breeding sites in Sweden and wintering areas in sub-Saharan Africa perform the desert crossing with respect to route choice, winds, timing and speed of migration by analysing 72 geolocator tracks recording migration. The swifts cross western Sahara on a broad front in autumn, while in spring they seem to use three alternative routes across the Sahara, a western, a central and an eastern route across the Arabian Peninsula, with most birds using the western route. The swifts show slower migration and travel speeds, and make longer detours with more stops in autumn compared with spring. In spring, the stopover period in West Africa coincided with mostly favourable winds, but birds remained in the area, suggesting fuelling. The western route provided more tailwind assistance compared with the central route for our tracked swifts in spring, but not in autumn. The ultimate explanation for the evolution of a preferred western route is presumably a combination of matching rich foraging conditions (swarming insects) and favourable winds enabling fast spring migration. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.
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SALAMA, Fawzy Mahmoud, Monier Mohammed ABD EL-GHANI, Ahmed Abd El Rahman AMRO, Ali El Saeid GAAFAR, and Ayat Abd El Monem ABD EL-GALIL. "Vegetation Dynamics and Species Diversity in a Saharan Oasis, Egypt." Notulae Scientia Biologicae 10, no. 3 (2018): 363–72. http://dx.doi.org/10.15835/nsb10310296.
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The present study provides an analysis of the floristic composition, habitat types, vegetation structure and species diversity, elucidating the role of the environmental factors that affect species distribution in Kharga Oasis, Western Desert, Egypt. The vegetation was sampled from 89 permanently visited stands in 12 sites situated along N - S line transect across the oasis, and extending for about 185 km to cover as much as possible the physiognomic variation in habitats. Four main habitats were recognized and forming concentric zones (from inside to outside): farmlands and date-palm orchards represent the inner zone, the waste-salinized lands (not saltmarshes) in the middle zone, and the surrounding (bounding) desert in the outer zone. A total of 122 species from 35 families and 102 genera represented the flora of the study area. Poaceae, Asteraceae and Fabaceae were the major families, which constituted 47% of the total flora. Classification using Bray-Curtis cluster analysis produced 4 vegetation groups (A - D); each can be linked to a certain habitat. The arrangement of habitat zones along the first DCA axis can be noticed: outer zone (bounding desert), middle zone (waste-salinized lands) and inner zone (arable lands). On the other hand, farmlands and date-palm orchard groups were separated from each other along the second DCA axis. The relationship between the vegetation and soil variables was studied using Canonical Correspondence Analysis (CCA); it was indicated the most important environmental gradients those control the vegetation composition and the distribution pattern of species in Kharga Oasis, which were mainly related to gradients in soil moisture content and fine fractions. The present situation of Kharga Oasis urges the conservation of some old historic wells and the naturally growing open dom-palm forests before vanishing due to high human activities in the area.
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Slimane, Laribi, Ghaitaoui Touhami, Arama Fatima Zohra, and Tahar Touahri. "Experimental Analysis of the Degradation of PV UDTS-50 W Modules Exposed to Extreme Weather Conditions in a Saharan Environment." Applied Mechanics and Materials 905 (February 15, 2022): 21–28. http://dx.doi.org/10.4028/p-nx91mc.
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The degradation of the electrical performance of photovoltaic modules UDTS-50W exposed to the sun for a long period of about 10 years in a Saharan environment of Adrar was presented. In this article, the experimental results obtained during the analysis of the I-V characteristics of some UDTS-50W photovoltaic modules tested in the real conditions of the Saharan environment (Adrar region). The electrical performance degradation of the UDTS-50 W PV modules was identified by empirically analyzing the I-V and P-V characteristics and by visual field inspection of these modules, which were installed in a renewable research unit in a desert environment (URERMS). The comparison between the experimental characteristic curves IV and PV of the PV modules UDTS-50W and the reference in the standard test conditions (STC) shows that the degradation of the electrical performances is due globally by the delamination and the discoloration of the Ethylene-vinyl acetate (EVA) encapsulate after the long term exposure in a desert environment.
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Soupiona, Ourania, Maria Mylonaki, Alexandros Papayannis, Athina Argyrouli, Panayotis Kokkalis, and Georgios Tsaknakis. "Seventeen-year systematic measurements of dust aerosol optical properties using the eole ntua lidar system (2000-2016)." EPJ Web of Conferences 176 (2018): 05029. http://dx.doi.org/10.1051/epjconf/201817605029.
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A comprehensive analysis of the seasonal variability of the optical properties of Saharan dust aerosols over Athens, Greece, is presented for a 17-year time period (2000-2016), as derived from multi-wavelength Raman lidar measurements (57 dust events with more than 80 hours of measurements). The profiles of the derived aerosol optical properties (aerosol backscatter and extinction coefficients, lidar ratio and aerosol Ångström exponent) at 355 nm are presented. For these dust events we found a mean value of the lidar ratio of ~52±13 sr at 355 nm and of ~58±8 sr (not shown) at 532 nm (2-4 km a.s.l. height). For our statistical analysis, presented here, we used monthly-mean values and time periods under cloud-free conditions. The number of dust events was greatest in late spring, summer, and early autumn periods. In this paper we also present a selected case study (04 April 2016) of desert dust long-range transport from the Saharan desert.