Letteratura scientifica selezionata sul tema "Sahel central"
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Articoli di riviste sul tema "Sahel central":
1
Diba, Ibrahima, Moctar Camara, Alioune Sarr e Arona Diedhiou. "Potential Impacts of Land Cover Change on the Interannual Variability of Rainfall and Surface Temperature over West Africa". Atmosphere 9, n. 10 (28 settembre 2018): 376. http://dx.doi.org/10.3390/atmos9100376.
Abstract (sommario):
We used the Abdu Salam International Centre for Theoretical Physics (ICTP) Regional Climate Model version 4.5 (RegCM4.5), to investigate the potential impacts of land cover change of the Sahel–Sahara interface on the West African climate over an interannual timescale from 1990 to 2009. A simulation at 50 km grid spacing is performed with the standard version of the RegCM4.5 model (control run), followed by three vegetation change experiments at the Sahel-Sahara interface (15° N and 20° N): forest, tall grass, and short grass savanna. The impacts of land cover change are assessed by analyzing the difference between the altered runs and the control one in different sub-domains (western Sahel, central Sahel, eastern Sahel, and Guinea). Results show that the presence of forest, tall grass, and short grass savanna at the Sahel–Sahara interface tends to decrease the mean summer surface temperature in the whole domain. Nevertheless, this decrease is more pronounced over the Central Sahel when considering the forest experiment. This temperature decrease is associated with a weakening (strengthening) of the sensible (latent) heat flux in the whole domain. An analysis of the radiation field is performed to better explain the changes noted in the latent heat flux, the sensible heat flux, and the surface temperature. When considering the rainfall signal, the analysis shows that the afforestation options tend to alter the precipitation in the considered sub-domains substantially by increasing it in the whole Sahel region, with strong interannual variability. This rainfall increase is associated with an increase of the atmospheric moisture. Finally, we investigated the impacts of the afforestation options on some features of the rainfall events, and on the atmospheric dynamics during wet and dry years. All afforestation options tend to increase the frequency of the number of rainy days in regions located south of 18° N during both periods. Nevertheless, this increase is stronger over the Central and Eastern Sahel during wet years in the forest case. All afforestation experiments induce an increase (decrease) of the low-levels monsoon flux in the Eastern Sahel (western Sahel) during both periods. At the mid-levels, the three afforestation options tend to move northward and to decrease the intensity of the African Easterly Jet (AEJ) south of 13° N during wet and dry years.The intensity of the AEJ is weaker during the wet period. The vegetation change experiments also affect the Tropical Easterly Jet (TEJ), especially during wet years, by increasing its intensity over the southern Sahel. The analysis of the activity of African Easterly Waves (AEWs) patterns exhibits a decrease of the intensity of these disturbances over the Sahel during both periods. This may be due to the weakening of the meridional temperature contrast between the continent and the Gulf of Guinea due to the Sahel–Sahara surface temperature cooling induced by the afforestation. In summary, this study shows that during both periods, the increase of the atmospheric moisture due to the afforestation is associated with favorable AEJ/TEJ configurations (weaker and northward position of the AEJ; stronger TEJ) which in turn may create a stronger convection and then, an increase in the Sahel rainfall. This Sahel rainfall increase is associated with a strengthening of the intense and heavy rainfall events which may impact diversely local populations.
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Vircoulon, Thierry. "Quand le Sahel central rencontre l’Afrique centrale, réflexions sur le conflit centrafricain". Hérodote N°179, n. 4 (2020): 56. http://dx.doi.org/10.3917/her.179.0056.
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Monerie, Paul-Arthur, Emilia Sanchez-Gomez, Marco Gaetani, Elsa Mohino e Buwen Dong. "Future evolution of the Sahel precipitation zonal contrast in CESM1". Climate Dynamics 55, n. 9-10 (17 agosto 2020): 2801–21. http://dx.doi.org/10.1007/s00382-020-05417-w.
Abstract (sommario):
Abstract The main focus of this study is the zonal contrast of the Sahel precipitation shown in the CMIP5 climate projections: precipitation decreases over the western Sahel (i.e., Senegal and western Mali) and increases over the central Sahel (i.e., eastern Mali, Burkina Faso and Niger). This zonal contrast in future precipitation change is a robust model response to climate change but suffers from a lack of an explanation. To this aim, we study the impact of current and future climate change on Sahel precipitation by using the Large Ensemble of the Community Earth System Model version 1 (CESM1). In CESM1, global warming leads to a strengthening of the zonal contrast, as shown by the difference between the 2060–2099 period (under a high emission scenario) and the 1960–1999 period (under the historical forcing). The zonal contrast is associated with dynamic shifts in the atmospheric circulation. We show that, in absence of a forced response, that is, when only accounting for internal climate variability, the zonal contrast is associated with the Pacific and the tropical Atlantic oceans variability. However, future patterns in sea surface temperature (SST) anomalies are not necessary to explaining the projected strengthening of the zonal contrast. The mechanisms underlying the simulated changes are elucidated by analysing a set of CMIP5 idealised simulations. We show the increase in precipitation over the central Sahel to be mostly associated with the surface warming over northern Africa, which favour the displacement of the monsoon cell northwards. Over the western Sahel, the decrease in Sahel precipitation is associated with a southward shift of the monsoon circulation, and is mostly due to the warming of the SST. These two mechanisms allow explaining the zonal contrast in precipitation change.
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Schewe, Jacob, e Anders Levermann. "Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming". Earth System Dynamics 8, n. 3 (5 luglio 2017): 495–505. http://dx.doi.org/10.5194/esd-8-495-2017.
Abstract (sommario):
Abstract. Projections of the response of Sahel rainfall to future global warming diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of abrupt transitions in response to gradual forcing. Here we present climate modeling evidence for the possibility of an abrupt intensification of Sahel rainfall under future climate change. Analyzing 30 coupled global climate model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300 % over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the tropical Atlantic and Mediterranean moisture source regions, intensifying abruptly beyond a certain SST warming level. We argue that this behavior is consistent with a self-amplifying dynamic–thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under warming could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.
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Rangel de Moraes, Fernanda. "Mudanças climáticas, conflitualidades e sistemas de crises no Sahel (África ocidental)". Boletim GeoÁfrica 1, n. 1 (18 aprile 2022): 76–90. http://dx.doi.org/10.59508/geoafrica.v1i1.51609.
Abstract (sommario):
A região da África ocidental conhecida como Sahel é palco de diversas tensões e conflitos que a definem como um espaço geopoliticamente instável. A conflitualidade regional do Sahel é alimentada por um conjunto de problemas estruturais e conjunturais de naturezas diferentes que se articulam de forma complexa e multiescalar. O objetivo central deste trabalho é analisar os efeitos das mudanças climáticas nas crises e conflitos e existentes no Sahel. A metodologia objetiva elaborar um marco conceitual valorizando uma perspectiva de análise sistêmica, com o conceito de sistema regional de crise estruturando nossa abordagem. Sendo assim, concluiu-se que as mudanças climáticas estão realmente gerando uma grande ameaça à segurança regional, não apenas pela escassez hídrica, insegurança alimentar, prevalência de doenças, alteração nas linhas de costa e a redistribuição da população, mas também por inflamar antigos conflitos e gerar novas tensões em um ambiente tão complexo como Sahel, tomando o papel de multiplicador de ameaças e catalisador da disseminação e longevidade dos conflitos.
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Marteau, Romain, Vincent Moron e Nathalie Philippon. "Spatial Coherence of Monsoon Onset over Western and Central Sahel (1950–2000)". Journal of Climate 22, n. 5 (1 marzo 2009): 1313–24. http://dx.doi.org/10.1175/2008jcli2383.1.
Abstract (sommario):
Abstract The spatial coherence of boreal monsoon onset over the western and central Sahel (Senegal, Mali, Burkina Faso) is studied through the analysis of daily rainfall data for 103 stations from 1950 to 2000. Onset date is defined using a local agronomic definition, that is, the first wet day (>1 mm) of 1 or 2 consecutive days receiving at least 20 mm without a 7-day dry spell receiving less than 5 mm in the following 20 days. Changing either the length or the amplitude of the initial wet spell, or both, or the length of the following dry spell modifies the long-term mean of local-scale onset date but has only a weak impact either on its interannual variability or its spatial coherence. Onset date exhibits a seasonal progression from southern Burkina Faso (mid-May) to northwestern Senegal and Saharian edges (early August). Interannual variability of the local-scale onset date does not seem to be strongly spatially coherent. The amount of common or covariant signal across the stations is far weaker than the interstation noise at the interannual time scale. In particular, a systematic spatially consistent advance or delay of the onset is hardly observed across the whole western and central Sahel. In consequence, the seasonal predictability of local-scale onset over the western and central Sahel associated, for example, with large-scale sea surface temperatures, is, at best, weak.
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Koné, Brahima, Arona Diedhiou, Adama Diawara, Sandrine Anquetin, N'datchoh Evelyne Touré, Adama Bamba e Arsene Toka Kobea. "Influence of initial soil moisture in a regional climate model study over West Africa – Part 1: Impact on the climate mean". Hydrology and Earth System Sciences 26, n. 3 (11 febbraio 2022): 711–30. http://dx.doi.org/10.5194/hess-26-711-2022.
Abstract (sommario):
Abstract. The impact of soil moisture initial conditions on the mean climate over West Africa was examined using the latest version of the regional climate model of the International Centre for Theoretical Physics (RegCM4) at a 25 km horizontal resolution. The soil moisture reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis of the 20th century (ERA-20C) was used to initialize the control experiment, while its minimum and maximum values over the entire domain were used to establish the respective initial dry and wet soil moisture conditions (hereafter referred to as dry and wet experiments, respectively). For the respective control, wet and dry experiments, an ensemble of five runs from June to September was performed. In each experiment, we analyzed the two idealized simulations most sensitive to the dry and wet soil moisture initial conditions. The impact of soil moisture initial conditions on precipitation in West Africa is linear over the Central and West Sahel regions, where dry (wet) experiments lead to a rainfall decrease (increase). The strongest precipitation increase is found over the West Sahel for wet experiments, with a maximum change value of approximately 40 %, whereas the strongest precipitation decrease is found for dry experiments over the Central Sahel, with a peak change of approximately −4 %. The sensitivity of soil moisture initial conditions can persist for 3–4 months (90–120 d) depending on the region. However, the influence on precipitation is no longer than 1 month (between 15 and 30 d). The strongest temperature decrease is located over the Central and West Sahel, with a maximum change of approximately −1.5 ∘C in wet experiments, whereas the strongest temperature increase is found over the Guinea coast and Central Sahel for the dry experiments, with a maximum change of around 0.6 ∘C. A significant impact of soil moisture initial conditions on the surface energy fluxes is noted: in the wet (dry) experiments, a cooling (warming) of the surface temperature is associated with a decrease (increase) in sensible heat flux, an increase (decrease) in latent heat flux and a decrease (increase) in the boundary layer depth. Part 2 of this study (Koné et al., 2022) investigates the influence of soil moisture initial conditions on climate extremes.
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D'Andrea, A. C., S. Kahlheber, A. L. Logan e D. J. Watson. "Early domesticated cowpea (Vigna unguiculata) from Central Ghana". Antiquity 81, n. 313 (1 settembre 2007): 686–98. http://dx.doi.org/10.1017/s0003598x00095661.
Abstract (sommario):
From examining the remains of charred cowpeas from rock shelters in Central Ghana, the authors throw light on the subsistence strategies of the Kintampo people of the second millennium BCE. Perhaps driven southwards from the Sahel by aridification, the Kintampo operated as both foragers and farmers, cultivating selected plants of the West African tropics, notably cowpea, pearl millet and oil palm.
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Li, Laifang, Raymond W. Schmitt, Caroline C. Ummenhofer e Kristopher B. Karnauskas. "North Atlantic salinity as a predictor of Sahel rainfall". Science Advances 2, n. 5 (maggio 2016): e1501588. http://dx.doi.org/10.1126/sciadv.1501588.
Abstract (sommario):
Water evaporating from the ocean sustains precipitation on land. This ocean-to-land moisture transport leaves an imprint on sea surface salinity (SSS). Thus, the question arises of whether variations in SSS can provide insight into terrestrial precipitation. This study provides evidence that springtime SSS in the subtropical North Atlantic ocean can be used as a predictor of terrestrial precipitation during the subsequent summer monsoon in Africa. Specifically, increased springtime SSS in the central to eastern subtropical North Atlantic tends to be followed by above-normal monsoon-season precipitation in the African Sahel. In the spring, high SSS is associated with enhanced moisture flux divergence from the subtropical oceans, which converges over the African Sahel and helps to elevate local soil moisture content. From spring to the summer monsoon season, the initial water cycling signal is preserved, amplified, and manifested in excessive precipitation. According to our analysis of currently available soil moisture data sets, this 3-month delay is attributable to a positive coupling between soil moisture, moisture flux convergence, and precipitation in the Sahel. Because of the physical connection between salinity, ocean-to-land moisture transport, and local soil moisture feedback, seasonal forecasts of Sahel precipitation can be improved by incorporating SSS into prediction models. Thus, expanded monitoring of ocean salinity should contribute to more skillful predictions of precipitation in vulnerable subtropical regions, such as the Sahel.
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Diba, Ibrahima, Moctar Camara e Arona Diedhiou. "Investigating West African Monsoon Features in Warm Years Using the Regional Climate Model RegCM4". Atmosphere 10, n. 1 (10 gennaio 2019): 23. http://dx.doi.org/10.3390/atmos10010023.
Abstract (sommario):
This study investigates the changes in West African monsoon features during warm years using the Regional Climate Model version 4.5 (RegCM4.5). The analysis uses 30 years of datasets of rainfall, surface temperature and wind parameters (from 1980 to 2009). We performed a simulation at a spatial resolution of 50 km with the RegCM4.5 model driven by ERA-Interim reanalysis. The rainfall amount is weaker over the Sahel (western and central) and the Guinea region for the warmest years compared to the coldest ones. The analysis of heat fluxes show that the sensible (latent) heat flux is stronger (weaker) during the warmest (coldest) years. When considering the rainfall events, there is a decrease of the number of rainy days over the Guinea Coast (in the South of Cote d’Ivoire, of Ghana and of Benin) and the western and eastern Sahel during warm years. The maximum length of consecutive wet days decreases over the western and eastern Sahel, while the consecutive dry days increase mainly over the Sahel band during the warm years. The percentage of very warm days and warm nights increase mainly over the Sahel domain and the Guinea region. The model also simulates an increase of the warm spell duration index in the whole Sahel domain and over the Guinea Coast in warm years. The analysis of the wind dynamic exhibits during warm years a weakening of the monsoon flow in the lower levels, a strengthening in the magnitude of the African Easterly Jet (AEJ) in the mid-troposphere and a slight increase of the Tropical Easterly Jet (TEJ) in the upper levels of the atmosphere during warm years.
Tesi sul tema "Sahel central":
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Clanet, Jean-Charles. "Géographie pastorale au Sahel central". Paris 4, 1994. http://www.theses.fr/1994PA040312.
Abstract (sommario):
Ce travail qui porte sur la "géographie pastorale au sahel central", a suivi durant vingt-cinq ans les communautés toubou, touarègue, peule et arabe des éleveurs nomadisant dans le nord du Burkina-Faso, de l'est du Niger et la partie du Tchad médian d'ouest en est, vaste ensemble de régions correspondant à la partie aride du bassin versant du lac Tchad. Pour suivre l'ensemble des tribus prises en compte, nous avons développé une méthode graphique originale permettant d'analyser l'évolution spatiale des aires pastorales exploitées par les éleveurs sahéliens. Les variations de positions consécutives aux deux sècheresses 1969-1974 et 1984-1985 montrent à quel point ces systèmes pastoraux ont été durement frappés dans leur économie au cours des deux dernières décennies. Néanmoins en dépit des péjorations majeures et des pertes irréversibles subies par leur environnement, la plupart des communautés ont surmonté tant bien que mal les deux derniers épisodes arides. Les plus mobiles conservent encore un nomadisme efficace centre sur le Sahel, un tiers d'entre elles a émigré en zone soudanienne, tandis qu'un dixième des familles a abandonné l'élevage. Au-delà de ces scores inégaux, l'insertion de l'élevage nomade dans le domaine agricole soudanien pose le problème de la coexistence de deux modes extensifs d'exploitation du milieu naturel, alors que l'aridification générale et la croissance démographique réduisent les terres à parcours et agricoles disponiblesThis study, which turns on "pastoral geography in central Sahel", has followed for twenty five years, the Tibu, Fulani, Tuareg and Arab communities of wandering breeders in north Burkina, east Niger and part of Chad, broad expanse of countries corresponding to the Chad arid basin. To follow the whole tribes taken for examples, we have developed an original graphic method permitting analysing the special evolutions of pastoral areas ran by sahelian breeders. Variations of positions consecutive of the two dryness 1969-1974 and 1984-1985 show up to which point, these pastoral systems have been hardly stroken about their economy during the last two decades. Yet, in spite of major disparaging senses and irreversible run suffered by their environment, most of communities have surmounted somehow or other the last two arid sessions. The more mobile still keep an effectual wandering life based on the Sahel, a third of them has migrated to Sudanian zone, whereas a tenth of families has given up breeding. Beyond these unequal scores, the normal rearing insertion in Sudanian zone agricultural scope show off the problem of coexistence between two extensible modes of running natural spots, even when general barrenlessing and population growth reduce available agricultural and routing lands
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Malam, Moussa Ahmad Tijani. "Le choix des lieux de développement au Sahel : l'exemple de la région de Maradi, Niger central". Rouen, 2003. http://www.theses.fr/2003ROUEL439.
Abstract (sommario):
Le modèle "zonal" de développement appliqué au Sahel découpe l'espace en quasi-territoires étanches et distincts les uns des autres, occupés par des populations aux genres de vie exclusifs. L'Etat, principal acteur de "développement des zones rurales" au Sahel se base sur ce modèle. Les directions départementales (ou régionales) du Plan auquelles se réfèrent assez souvent les techniciens des projets et O. N. G. , mettent en avant l'étude des potentialités physiques des régions à partir desquelles elles établissent un zonage agro-écologique qui sert de base pour l'implantation des projets de développement. Or le Sahel est un espace qui n'est pas viable sans la circulation et les échanges ; "complémentarité et solidarité interzonales s'ordonnent mieux dans un réseau de relations méridiennes que dans une opposition et un découpage latitudinaux". C'est ce que Retaillé appelle le modèle sahélien ; c'est ce modèle qu'il a décrit déjà en 1982 en prenant comme laboratoire la région du koutous et le département de Zinder dans le centre-est du Niger. C'est ce modèle que nous avons voulu vérifier et valider dans la région de Maradi au Niger centralThe "zonal" model of development applying to Sahel, organise the space in distinct territories, isolated from each other, occupied by population with their own exclusive way of life ; the state, as the main character of the "rural area development" in Sahel, is based on that model. District or region management for the plan to which the technician (project and N. G. O. ) often refer, put forward the study of physical potentialities of the areas from which they establish strict agro-ecological deferenciation that is the base for the organisation od development pproject. However, Sahel is a space that is not viable without exchanges and movement of population ; "solidarity and complementarity between the different areas organise theirselves better on a network of meridian relations much more than in a latitudinal opposition" That is what Retaillé calls the sahelian model of development ; that is the model he has described in 1982, basing his studies on the koutous area and Zinder district in the centre-east Niger. This is the model we wanted to check and validate in the Maradi area, central Niger
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Durand, Alain. "Enregistrement sédimentaire de la dynamique climatique au quaternaire supérieur dans le sahel central (Niger et Tchad)". Dijon, 1993. http://www.theses.fr/1993DIJOS053.
Abstract (sommario):
Un essai de synthèse de la dynamique sédimentaire actuelle au sahel central a été tente en préalable à l'analyse paléoclimatique. Au quaternaire supérieur, on observe la prédominance de phénomènes alluviaux et éoliens dans un cadre structural instable. Mais les conditions climatiques du sahel central semblent être restées dans les limites des variations observées depuis le début du siècle. Le maximum aride kanémien situe entre 19,000 et 15,000 ans 14c b. P. , comprend en fait trois épisodes de moins d'un millénaire chacun, et n'ayant connu un recul des isohyètes vers le sud que de 150 a 300 km par rapport à la situation moyenne récente. Inversement, il n'a pas été observe de dépôt date directement de 6000 ans 14c b. P. Et dont les caractéristiques paléoécologies, sédimentologies et topographiques étaient susceptibles de correspondre a un megatchad de 330000 km#2 pour un niveau de 325 m. Par contre des déplacements verticaux de plusieurs dizaines de mètres sont attestes a l'holocène. Le cordon périlacustre de 325 m, le réseau hydrographique, certaines particularités hydrogéologiques et même certaines morphologies éoliennes s'expliquent par une origine structurale et une néotectonique active. Par analogie avec les sècheresses récentes, un essai d'interprétation des crises d'aridité du tardiglaciaire a été tente. Ces changements abrupts sont lies aux aérojets d'est, dans le cadre de la circulation atmosphérique zonale qui évolue en fonction de la circulation océanique globale. Le facteur déclenchant l'aridité serait une faible variation de la salinité des eaux de surface de l'atlantique nord
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Andre, Camille. "Bolloré Transport & Logistics face au risque géopolitique au Sahel central (janvier 2013-mai 2021) : analyse spatiale, quantitative et des jeux d’acteurs : l’apport de la méthode géopolitique à la compréhension des contextes d’opération dégradés". Electronic Thesis or Diss., Paris 8, 2021. http://www.theses.fr/2021PA080074.
Abstract (sommario):
Le Sahel central connaît depuis la chute du Mali en 2012 d’importantes problématiques sécuritaires. Après s’être accaparé la rébellion touarègue nord-malienne, les groupes armés djihadistes ont été contraints à la clandestinité par l’intervention extérieure française dès janvier 2013. Ces événements de 2012-2013 interviennent dans un contexte géopolitique et politique déjà complexe où de nombreux types d’acteurs évoluent (djihadistes, narcotrafiquants, groupes armés touaregs, milices d'auto-défense, civils, politiques …), chacun avec leurs stratégies propres et leurs représentations. Cette thèse CIFRE part du postulat que de nombreux événements et points de ruptures étaient prévisibles et que certaines dynamiques futures pourront l’être grâce à une approche méthodologique singulière. Ce travail mobilise la méthode géopolitique, constituant un biais d’appréhension qui se concentre sur l’analyse spatiale et multiscalaire ; sur l’analyse des acteurs et de leurs représentations et sur la constitution de plusieurs bases de données (événements armés et politiques) afin d’en extraire des analyses quantitatives et qualitatives. De cette thèse ressort la possibilité de monitorer l’étude quotidienne d’un territoire et ainsi repérer les signaux faibles des mutations géopolitiques, sécuritaire, politique. La méthode géopolitique apporte un éclairage sur la compréhension des dynamiques conflictuelles et des risques (géopolitiques, sécuritaires, politiques, réputationnels) que le contexte d’opération fait peser sur Bolloré Transport & Logistics et, plus largement, sur les acteurs économiques présents dans la zone qui se doivent de protéger leurs effectifs humains, matériels, leurs chaînes d’approvisionnement et leur réputationSince the fall of Mali in 2012, the central Sahel has been experiencing major security issues. After cornering the Northern Malian Tuareg rebellion, jihadist armed groups were forced into hiding by the French external intervention as early as January 2013. These 2012-2013 events take place in an already complex geopolitical and political context where many types of actors are evolving (jihadists, drug traffickers, Tuareg armed groups, self-defense militias, civilians, politicians ...), each with their own strategies and representations. This CIFRE thesis starts from the premise that many events and breaking points were predictable and that certain future dynamics could be foreseen thanks to a singular methodological approach. This essay uses the geopolitical method, constituting a means of understanding that focuses on spatial and multiscalar analysis; on the analysis of actors and their representations and on the constitution of several databases (armed and political events) in order to extract quantitative and qualitative analyses. From this thesis emerges the possibility of monitoring the daily study of a territory and thus identifying the weak signals of geopolitical, security and political changes. The geopolitical method sheds light on the conflictual dynamics and risks (geopolitical, security, political, reputational) that the business context poses for Bolloré Transport & Logistics and, more broadly, for the economic actors present in the area who must protect their staff and equipment, their supply chains and their reputation
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Hassane, Bouba. "Variabilité de la dynamique éolienne au sol (direction et vitesse du vent) et de ses conséquences (visibilité horizontale) au Sahel central et Sahara méridional entre 1950 et 2009 (exemple de quelques stations synoptiques au Niger)". Rouen, 2013. http://www.theses.fr/2013ROUES012.
Abstract (sommario):
Au Sahel, la variabilité climatique a d'abord été analysée à partir de la pluviométrie. Mais celle-ci ne concerne que quelques dizaines de jours dans l'année, alors que les jours sans vent sont peu fréquents. La variabilité climatique est donc analysée ic à partir de l'analyse de la dynamique éolienne au sol et de ses conséquences en lien avec la dégradation environnementale entre 1950 et 2009. - Appréhender les variations climatiques à partir de la direction et de la vitesse du vent mesurées par les stations synoptiques (TCM). Les variations journalières reflètent le rôle de la turbulence thermique. Les cycles saisonniers sont distingués par les directions et les vitesses du vent en lien avec les mouvements de la ZCIT et du FIT. Les périodes de forte aridité sont mises en évidence par des baisses significatives des vitesses moyennes. Les vents au sol distinguent différents types de sécheresses, ce que la pluviométrie ne permettait pas. Ainsi donc, les mesures d'observation du vent fournies par les stations synoptiques aboutissent à des résultats homogènes et en conformité avec les connaissances antérieures issues principalement de l'analyse d'autres paramètres. Ces mesures météorologiques sont donc fiables et d'un intérêt certain. - Comparer les observations météorologiques des vents avec les réanalyses 20CR, NNR-1, ERA-40 et ERA-Interim. Les séries mensuelles présentent de bonnes corrélations à Niamey et Maïné-Soroa, mais pas à Bilma. L'analyse du cycle annuel montre de fortes sur/sous-estimations des vents par les réanalyses. L'évolution interannuelle des vents en été (JJA) et hiver (DJF) montre que ces discordances varient selon les vents, les stations, les périodes et les réanalyses. Au total, ce sont donc ERA-40 et NNR-1 qui sont les plus proches des observations alors que 20CR s'écarte le plus fortement. La comparaison des observations avec les mesures météorologiques assimilées par NCAR (SYNOP) indique que les faibles corrélations des réanalyses avec les mesures TCM pourraient être liées aux fichiers SYNOP en raison de l'importance des données manquantes ou erronées. - Analyser la variation de la conséquence combinée des variations pluviométriques et des vents à travers la visibilité horizontale et les types de temps liés aux basses visibilités (chasses-sables, brumes de sable et brumes-sèches). Les variations interannuelles indiquent des baisses importantes de la visibilité en lien avec les variations de la pluviométrie. Mais l'augmentation des phénomènes météorologiques liés aux basses visibilités indique aussi un changement climatique plus précoce que ce qui est généralement admis sur la base de la seule évolution pluviométrique. Ces modifications concernent la zone saharienne, la plus sensible à l'érosion éolienne, dès la fin des années 1950. Pour les stations sahéliennes, une première dégradation est visible vers 1970, puis une seconde au début des années 1980. Il est possible qu'une nouvelle dégradation observable uniquement à Niamey dans les années 1990 et 2000 soit d'origine anthropique. Analyser la relation vitesse du vent-visibilité horizontale au cours du cycle annuel. Compte-tenu du gradient pluviométrique et de la position amont-aval des stations sur la trajectoire éolienne d'échelle continentale NE-SW, nous observons une évolution qui laisse supposer qu'interviennent d'autres facteurs. En effet, on passe progressivement d'un véritable cycle d'hystérésis à Maïné-Soroa en période humide à une forte relation binaire que vient à peine perturber une courte saison des pluies à Nguigmi en période aride. On peut donc supposer une relation binaire : s'agit-il de la végétation ou d'un facteur anthropique ?
6
Henry, Jean-Pierre. "Stratégies paysannes dans une zône sahelo-soudanienne fort peuplée l'arrondissement de Matamèye, Niger central". Lille 3 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37598359g.
7
You, Qing [Verfasser], e Bernhard A. [Gutachter] Sabel. "The role of physicochemical parameters on polybutylcyanoacrylate nanoparticles' delivery to the central nervous system / Qing You ; Gutachter: Bernhard A. Sabel". Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1220036072/34.
8
You, Qing Verfasser], e Bernhard A. [Gutachter] [Sabel. "The role of physicochemical parameters on polybutylcyanoacrylate nanoparticles' delivery to the central nervous system / Qing You ; Gutachter: Bernhard A. Sabel". Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1220036072/34.
9
Tawfik, Mohamed [Verfasser], e Bernhard A. [Gutachter] Sabel. "Nanoparticles delivery to the central nervous system in-vivo : PVP nanoparticles for brain drug delivery and neuroprotection with siRNA-caspase-3 / Mohamed Tawfik ; Gutachter: Bernhard A. Sabel". Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2021. http://nbn-resolving.de/urn:nbn:de:gbv:ma9:1-1981185920-387735.
10
Ardoin-Bardin, Sandra. "Variabilité hydroclimatique et impacts sur les ressources en eau de grands bassins hydrographiques en zone soudano-sahélienne". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2004. http://tel.archives-ouvertes.fr/tel-00568025.
Abstract (sommario):
Pour les pays du sous-continent ouest africain soumis depuis une trentaine d'années à un changement climatique sans précédent au XXème siècle, la modélisation de l'impact de la variabilité prévisible du climat sur les ressources en eau est fondamentale pour la planification des aménagements. L'objectif de ce travail est l'utilisation de simulation de pluies et d'évapotranspiration potentielle issues de scénarii climatiques en entrée de modèles hydrologiques, calés pour les grandes rivières d'Afrique de l'Ouest (Sénégal, Gambie, Sassandra) et Centrale (Logone-Chari), afin d'étudier la variabilité probable des ressources en eau au cours du XXIème siècle. Cette approche se fonde sur : - la connaissance de la variabilité des régimes pluviométriques et hydrologiques. Globalement, la période 1970-1998 est déficitaire et la décennie 90 témoignent de la persistance de la sécheresse. Ces déficits peuvent s'expliquer par une variation de l'espace couvert par la mousson s'inscrivant dans une dynamique à l'échelle de la circulation atmosphérique générale ; - l'évaluation d'outils de modélisation des régimes hydrologiques des grands cours d'eau régionaux. Deux modèles de bilans hydrologiques (GR2M et WBM), fonctionnant au pas de temps mensuel sur des grilles à la résolution du demi degré carré, ont été retenus. L'analyse de sensibilité modèles montre l'importance des précipitations et des états de surface dans la modélisation hydrologique. Cette évaluation souligne également la performance et la robustesse du modèle GR2M ; - le développement et l'application de scénarii climatique à partir des données issues des Modèles de Circulation Générale. Les sorties de modèles climatiques ne sont pas vraiment fiables mais les variations prévues peuvent être combinées aux observations pour générer des scénarii climatiques. L'utilisation des données de précipitations et de température du modèle HadCM3-A2, via deux scénarii climatiques, dans les modèles hydrologiques GR2M et WBM conduisent à la diminution des débits du Sénégal et de la Gambie, une augmentation suivie d'une diminution des débits du Sassandra et une augmentation des débits du Logone-Chari.
Libri sul tema "Sahel central":
1
Lamine, Ridha. Villes et citadins du Sahel Central. Tunis: l'Or du temps, 2001.
2
Haour, Anne. Rulers, warriors, traders, clerics: The central Sahel and the North Sea, 800-1500. Oxford: Published for the British Academy by Oxford University Press, 2007.
3
Haour, Anne. Rulers, warriors, traders, clerics: The central Sahel and the North Sea, 800-1500. Oxford: Published for the British Academy by Oxford University Press, 2007.
4
Sorieul, Françoise. Profil de la recherche et des besoins en information scientifique et technique du Centre Sahel. Québec, Canada: Centre Sahel, Université Laval, 1992.
5
Brahim, Fawzi. Le Sahel Centeral et Méridional, tunisie orientale: Géomorphologir et dynamique récent en milieu naturel. Tunis: Ibn Zeidoun éd., 2005.
6
Saheli Women's Resource Centre (New Delhi, India). 25 years of continuity-- and change. New Delhi: Saheli, 2006.
7
Gronenborn, Detlef. States and Trade in the Central Sahel. Oxford University Press, 2013. http://dx.doi.org/10.1093/oxfordhb/9780199569885.013.0058.
8
Toulmin, Camilla. Land, Investment, and Migration. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198852766.001.0001.
Abstract (sommario):
How do people survive and thrive in the uncertain and risk-prone Sahel? This long-term study portrays the people of Dlonguébougou in Central Mali, to show how they have adapted to change over the last 35 years, shaping new strategies and finding new sources of cash. Drawing on my 2 years in the village in 1980–1982, published in Cattle, Women, and Wells: Managing Household Survival in the Sahel (OUP 1992), I have revisited the people to explore the village economy and society today. A tripling in population, unpredictable rainfall, and the arrival of the Chinese have forced people into new ways of both making ends meet and building up wealth—some are doing much better than others. Using a combination of infographics, satellite images, interviews, and survey data, my research presents the different strategies and fortunes of individuals and their families, the search for new cash incomes, the shift of people from village to town, and the erosion of collective solidarity at household and village levels. Overall, people’s fortunes have been mixed. Many people acknowledge they have become financially better off, but they are no longer so rooted in the life and landscape of millet farming, which had structured household relationships and village society. Land has become much scarcer, and the villagers can no longer exert much power over the wider society and environment. In eight chapters, Land, Investment, and Migration is written in an engaging style, with plenty of illustrations and material from interviews.
9
Great Britain: Parliament: House of Commons: International Development Committee e Malcolm Bruce. Crisis in the Central African Republic: Oral and Written Evidence, 3 December 2013, Lynne Featherstone MP, Parliamentary under-Secretary of State, DFID, Andrew Mccoubrey, Deputy Head of Africa Regional Development, DFID and Rt Hon. Mr Stephen o'Brien MP, UK Special Envoy for the Sahel. Stationery Office, The, 2014.
10
Estimation des bilans fourragers dans la région du Sahel d'Afrique de l’Ouest et Centrale. FAO, 2020. http://dx.doi.org/10.4060/ca9111fr.
Capitoli di libri sul tema "Sahel central":
1
Sunday Ojo, John, e Oluwole Ojewale. "Gold Mining and Instability in the Central Sahel". In Governing Natural Resources for Sustainable Peace in Africa, 38–59. London: Routledge, 2023. http://dx.doi.org/10.4324/9781003355717-4.
2
Hilderbrand, Katherine. "Assessing the Components of Seasonal Stress Amongst Fulani of the Seno-Mango, Central Mali". In Population, Health and Nutrition in the Sahel, 254–88. London: Routledge, 2022. http://dx.doi.org/10.4324/9781315831794-13.
3
Eerenbeemt, Marie-Louise van den. "A Demographic Profile of the Fulani of Central Mali With Special Emphasis on Infant and Child Mortality". In Population, Health and Nutrition in the Sahel, 79–104. London: Routledge, 2022. http://dx.doi.org/10.4324/9781315831794-5.
4
Wagenaar-Brouwer, Martie. "Preliminary Findings on the Diet and Nutritional Status of Some Tamasheq and Fulani Groups in the Niger Delta of Central Mali". In Population, Health and Nutrition in the Sahel, 226–53. London: Routledge, 2022. http://dx.doi.org/10.4324/9781315831794-12.
5
Mortimore, Michael. "Changing Paradigms for People-Centred Development in the Sahel". In The End of Desertification?, 65–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-642-16014-1_3.
6
"Central Mali". In Jihadists of North Africa and the Sahel, 147–91. Cambridge University Press, 2020. http://dx.doi.org/10.1017/9781108771160.005.
7
Haour, Anne. "Sahelian frameworks". In Rulers, Warriors, Traders, Clerics. British Academy, 2007. http://dx.doi.org/10.5871/bacad/9780197264119.003.0002.
Abstract (sommario):
This chapter provides an overview of the current state of archaeological research in the central Sahel. Archaeological research on the central Sahel is still in its infancy while historical research is a little better advanced, focusing on the local dynastic lists and on their critique. Most of the published archaeological work about Sahel is still descriptive in nature rather than synthetic, highlighting the need for further research. This chapter describes some key areas in central Sahel based on available data including Darfur, Kanem-Borno, and southern Niger.
8
Haour, Anne. "Rulers". In Rulers, Warriors, Traders, Clerics. British Academy, 2007. http://dx.doi.org/10.5871/bacad/9780197264119.003.0003.
Abstract (sommario):
This chapter compares the privileges and duties of rulers in central Sahel and north-west Europe. It provides a factual overview of the political history of the central Sahel and north-west Europe and compares their rulers in terms of boundary control, economic control and taxation, and religious and social roles. It suggests that many medieval polities in north-west Europe and central Sahel were the result of economic interference or of military campaigns imposing a new framework on disparate societies.
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Haour, Anne. "Traders". In Rulers, Warriors, Traders, Clerics. British Academy, 2007. http://dx.doi.org/10.5871/bacad/9780197264119.003.0005.
Abstract (sommario):
This chapter examines the similarities in the medieval Sahel and north-west Europe within the specific context of trade, and particularly of traders. It outlines the common themes of trade in central Sahel and north-west Europe including the mechanisms for the movement of goods and forms of trade. The findings indicate that the commerce in slaves is a strong thread of similarity and a concrete link between north-west Europe and the central Sahel.
10
Haour, Anne. "The case for comparison". In Rulers, Warriors, Traders, Clerics. British Academy, 2007. http://dx.doi.org/10.5871/bacad/9780197264119.003.0001.
Abstract (sommario):
This chapter explains the coverage of this book, which is about the comparison of rulers, warriors, traders, and clerics on the central Sahel and the North Sea region. It argues that there was more similarity between north-western Europe and the central Sahel in the few centuries either side of AD 1001 than has hitherto been recognised, and maintains that the nature of the sources has obscured these formative times and left them in the shadow of organised structures. It discusses the interconnectedness of central Sahel and north-west Europe through contacts and shared pre-industrial nature.
Rapporti di organizzazioni sul tema "Sahel central":
1
Desmidt, Sophie, Oriol Puig, Adrien Detges, Pia van Ackern e Fabien Tondel. Climate change and resilience in the Central Sahel. European Centre for Development Policy Management, giugno 2021. http://dx.doi.org/10.55317/casc011.
Abstract (sommario):
This policy paper summarises the main findings from research conducted under CASCADES on the Central Sahel, covering Burkina Faso, Mali and Niger. This research focused on key climate related challenges in the region, notably with regards to livelihoods, food security, human mobility and human security, including communal conflicts and violent extremism. The main conclusion is that climate change is and will be an important factor for the future of the Central Sahel. Both its current and future impacts, however, are intrinsically linked to socio-economic and political factors that must be emphasised when addressing climate-related challenges in the region. This policy paper is structured as follows. We first present a brief overview of expected climate impacts on the region, and their possible knock-on effects on livelihoods and food security, mobility, communal violence and violent extremism. We then go on to discuss some of the current policy responses and the challenges related to these issues; and summarise policy recommendations to address shortcomings in current approaches to climate risks in the Sahel. In closing, we look forward to how climate change impacts could unfold in the region.
2
Van Ackern, Pia, e Adrien Detges. Climate change, vulnerability and security in the Sahel. Adelphi research gemeinnützige GmbH, dicembre 2022. http://dx.doi.org/10.55317/casc024.
Abstract (sommario):
Climate change plays an important role in the future of the Sahel. Temperatures, particularly in the northern-central Sahel, could rise 1.5 times faster than the global average. Climate shocks and extreme events such as droughts and heavy rains are projected to become more frequent and severe. These changes are accompanied by other challenges: accelerated population growth, low economic productivity and production diversity, political conflicts and crises, inter-communal violence and violent extremism. However, the severity of climate impacts on livelihoods, food security, mobility and conflict in the Sahel will depend largely on the future evolution of socio-economic and political conditions in the region. These will ultimately determine the vulnerability and resilience of Sahelian communities to climate impacts. The evolution of these conditions is uncertain, but we can consider different scenarios to help Sahelian communities and decision-makers prepare for the possible challenges (and opportunities) ahead. Looking ahead to 2050, this paper presents three scenarios for the part of the Sahel comprising Burkina Faso, Mali and Niger. Each scenario is characterised by a different level of vulnerability and resilience to the future effects of climate change, depending on the social, political and economic parameters that characterise it. Thus, each scenario presents different challenges and opportunities for the security and development of the region. The main purpose of the scenarios is to describe and assess these challenges in order to facilitate anticipatory action. The scenarios presented in this document were developed jointly with 19 experts from the region, working in the fields of climate change adaptation, natural resource management, conflict prevention and other relevant sectors, in order to obtain a multidisciplinary perspective on the main challenges and solutions. The methodological approach is described in the annex. The scenarios presented here are not exhaustive. Rather, they are intended to provide an overview of different possible futures, to provide a basis for adaptation strategies, and to raise awareness among decision-makers and stakeholders in the EU and the Sahel more generally. In particular, the scenarios can be used as tools to identify relevant policy options in the face of uncertain climatic, social, political and economic conditions in the Sahel.
3
Benjaminsen, Tor A., Hanne Svarstad e Iselin Shaw of Tordarroch. Recognising Recognition in Climate Justice. Institute of Development Studies (IDS), ottobre 2021. http://dx.doi.org/10.19088/1968-2021.127.
Abstract (sommario):
We argue that in order to achieve climate justice, recognition needs to be given more attention in climate research, discourse, and policies. Through the analysis of three examples, we identify formal and discursive recognition as central types of recognition in climate issues, and we show how powerful actors exercise their power in ways that cause climate injustice through formal and discursive misrecognition of poor and vulnerable groups. The three examples discussed are climate mitigation through forest conservation (REDD), the Great Green Wall project in Sahel, and the narrative about climate change as a contributing factor to the Syrian war.
4
Delgado, Caroline, Kristina Tschunkert e Dan Smith. Food Insecurity in Africa: Drivers and Solutions. Stockholm International Peace Research Institute, gennaio 2023. http://dx.doi.org/10.55163/gisr2785.
Abstract (sommario):
This paper explores how climate change, violent conflict, the Covid-19 pandemic and the cost-of-living crisis combine to drive rapidly increasing levels of food insecurity. These drivers play out differently across and within regions and countries, and this paper focuses on how a combination of the drivers plays out on the African continent. It looks at four subregions—North Africa, the Horn of Africa, the Sahel, and Central and Southern Africa—and several countries within these regions. Africa is the continent with the highest proportion of people—just over 20 per cent— facing hunger. Africa also carries the heaviest burden from the impact of climate change. In 2021 18 countries in sub-Saharan Africa experienced armed conflicts. The economic fallout of climate change, conflict and the Covid-19 pandemic has widened inequality and sharpened societal divisions. Addressing the impacts of these compounding crises and breaking the vicious cycle of climate change, food insecurity and conflict requires a concerted effort by local, national, regional and global humanitarian, development and peacebuilding actors, governments and donors. To this end, the paper concludes with nine recommendations on the way forward.
5
Deb, Shourjya, e Virginie Baudais. The Challenges of Data Collection in Conflict-affected Areas: A Case Study in the Liptako-Gourma Region. Stockholm International Peace Research Institute, ottobre 2022. http://dx.doi.org/10.55163/vwim3307.
Abstract (sommario):
Conducting research in the Sahel has become more challenging over the past 10 years, and the continuing deterioration of the security situation has restricted access to many areas. This SIPRI Insights paper provides an overview of the main challenges for researchers when conducting data collection in conflict-affected areas. The paper employs a case study of a humanitarian protection project that SIPRI has been working on in the Liptako-Gourma region. The project was designed in collaboration with the Danish Refugee Council (DRC) and three local research partners: the Centre for Democratic Governance (CGD) in Burkina Faso, Point Sud in Mali and the Laboratoire d’Études et de Recherche sur les Dynamiques Sociales et le Développement Local (LASDEL) in Niger. Using the case study, the paper identifies and outlines how the project addressed specific challenges. The paper also highlights key considerations for researchers to take into account when carrying out data collection and fieldwork in conflict zones. Evidence-based research can influence humanitarian and development initiatives and support shifts in policy and programming. The bottom-up research approach gives a voice to communities and alternative perspectives and advances evidence-based solutions that are locally driven, meaningful and sustainable for target populations.
6
Military coups, jihadism and insecurity in the Central Sahel. Organisation for Economic Co-Operation and Development (OECD), maggio 2024. http://dx.doi.org/10.1787/522f69f1-en.