14 research outputs found
VariabilitĂ© interannuelle et intra-saisonniĂšre des prĂ©cipitations en relation avec les deux rĂ©gimes dâondes dâEst en Afrique de lâOuest
LâĂ©tude de la variabilitĂ© inter-annuelle et intra-saisonniĂšre des prĂ©cipitations en relation avec les deux rĂ©gimes dâondes dâest est menĂ©e en Afrique de lâOuest. La distribution spatiale des prĂ©cipitations en relation avec ces ondes montre quâelles contribuent Ă lâaugmentation des prĂ©cipitations dans la bande de latitude 7°N â 15°N, vers la zone de convergence inter tropicale (ZCIT), avec deux maxima prĂšs du Fouta- Djalon en GuinĂ©e et vers le Lac Tchad. Les ondes sont trĂšs actives en juillet et aoĂ»t oĂč les prĂ©cipitations sont abondantes et faibles en juin et septembre marquant le dĂ©but et la fin de la saison des pluies. Elles sont aussi trĂšs actives (faibles) pendant les Ă©tĂ©s Ă forte (faible) pluviomĂ©trie. Les deux rĂ©gimes dâondes dâEst sont diffĂ©rents et contribuent Ă accroĂźtre les prĂ©cipitations de maniĂšres diffĂ©rentes. Pour lâonde de 6 â 9-jours, il existe une extension zonale des anomalies positives des prĂ©cipitations dans la bande de latitude 7°N-15°N de lâEst Ă lâOuest de la zone dâĂ©tude, avec deux maxima prĂšs du Fouta-Djalon en GuinĂ©e et vers le Lac Tchad. Dans ce rĂ©gime, les maxima des anomalies positives des prĂ©cipitations sont associĂ©s Ă de fortes anomalies de la composante zonale du vent, et lâaccroissement des prĂ©cipitations est liĂ© Ă dâimportantes modulations du jet dâest africain (AEJ). Les deux maxima des anomalies positives des prĂ©cipitations apparaissant vers le Fouta-Djalon et vers le Lac Tchad coĂŻncident avec les maxima des composites des anomalies du flux zonal de vapeur dâeau associĂ© Ă lâonde de 6 â 9-jours dans la couche 850â500 hPa (maxima de flux dâOuest). Pour lâonde de 3 â 5-jours, il existe une forte extension mĂ©ridienne des anomalies des prĂ©cipitations dans la bande de latitude 5°N-15°N en relation avec lâextension mĂ©ridienne de la structure de lâonde. Dans ce rĂ©gime, il nây a quâun seul maximum, vers la GuinĂ©e, des composites des anomalies du flux zonal de vapeur dâeau (flux dâOuest) dans la couche 850 â 500 hPa. Ainsi, les deux rĂ©gimes dâondes dâEst contribuent Ă lâaccroissement des prĂ©cipitations dans la rĂ©gion du Fouta-Djalon, tandis que le maximum des prĂ©cipitations observĂ© vers le Lac Tchad serait dĂ» uniquement Ă lâonde de 6 â 9-jours.Mots-clĂ©s : onde de 6â9-jours, onde Africaine, structure spatiale, les anomalies des prĂ©cipitations, flux de vapeur dâeau
La maladie de von-hippel lindau dans une famille togolaise
La maladie de Von Hippel Lindau(VHL) est une affection hĂ©rĂ©ditaire autosomique dominante dont lâexpression phĂ©notypique est variable et multiviscĂ©rale. Le diagnostic nĂ©cessite des arguments cliniques et un plateau technique de pointe. nous rapportons les rĂ©sultats dâune enquĂȘte au sein dâune famille togolaise à partir de deux observations cliniques. Ces observations mettent en exergue les difficultĂ©s de la pratique mĂ©dicale en Afrique subsaharienne liĂ©es Ă un plateau technique inexistant
Frontiers of urban control: lawlessness on the city edge and forms of clientalist statecraft in Zimbabwe
This article develops the concept of âurban frontierâ to explore conflicts over state regularization of city edge informal settlements in Zimbabweâs capital Harare. It conceptualises the presence of âlawlessâ urban frontiers and âillegalâ territorial authorities in capital cities as expressions of a permissive form of central statecraft. In so doing, the article takes forward debates over the politics shaping the margins of Africaâs rapidly expanding cities, redressing scholarsâ tendency to neglect central party-state strategic calculations and party politics in their analyses of unregulated settlements. Dominant interpretations generally hinge on state absence or weakness and emphasise localised influences. The case of Harareâs highly politicized city-edge informal settlements reveals the inadequacy of apolitical approaches particularly clearly, as all were controlled by the ruling ZANUPF party. The conflicts provoked by regularization provide a lens on disputes within the ruling party, which we interpret as disputes over different forms of clientalist statecraft. Analyses of urban frontiers can thus help move away from generic one-size-fits-all explanations of informality and patronage politics in Africaâs expanding cities
Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients
Convection activity over the Guinean coast and Central Africa during northern spring from synoptic to intra-seasonal timescales
International audienceThis study proposes an overview of the main synoptic, medium-range and intraseasonal modes of convection and precipitation in northern spring (MarchâJune 1979â2010) over West and Central Africa, and to understand their atmospheric dynamics. It is based on daily National Oceanic and Atmospheric Administration outgoing longwave radiation and Cloud Archive User Service Tb convection data, daily TRMM and Global Precipitation Climatology Project rainfall products and daily ERA-Interim reanalysis atmospheric fields. It is first shown that mesoscale convective systems can be modulated in terms of occurrences number and intensity at such time scales. Based on empirical orthogonal function analyses on the 2â90-day filtered data it is shown that the main mode of convective and rainfall variability is located along the Guinean coast with a moderate to weak extension over Central Africa. Corresponding regressed deseasonalised atmospheric fields highlight an eastward propagation of patterns consistent with convectively coupled equatorial Kelvin wave dynamics. Then a singular spectrum analysis combined with a Hierarchical Ascendant Classification enable to define objectively the main spectral bands of variability within the 2â90-day band, and highlight three main bands, 2â8-, 8â22- and 20â90-day. Within these three bands, spaceâtime spectral decomposition is used to identify the relative impacts of convectively coupled equatorial Kelvin, Rossby and inertiaâgravity waves, as well as MaddenâJulian Oscillation (MJO) signal. It confirms that eastward propagating signals (convectively coupled equatorial Kelvin wave and MJO) are highly dominant in these convection and precipitation variability modes over the Guinean coast during northern spring. So, while rain-producing individual systems are moving westward, their activity are highly modulated by sub-regional and regional scales envelops moving to the east. This is a burning issue for operational forecasting centers to be able to monitor and predict such eastward propagating envelops of convective activity