Abdou Moumouni University

About: Abdou Moumouni University is a education organization based out in Niamey, Niamey, Niger. It is known for research contribution in the topics: Population & Agriculture. The organization has 796 authors who have published 808 publications receiving 17478 citations. The organization is also known as: University of Niamey & Abdou Moumouni Dioffo University.

Finding all efficient extreme points for multiple objective linear programs

Abstract: In this paper we develop a method for finding all efficient extreme points for multiple objective linear programs. Simple characterizations of the efficiency of an edge incident to a nondegenerate or a degenerate efficient vertex are given. These characterizations form the basis of an algorithm for enumerating all efficient vertices. The algorithm appears to have definite computational advantages over other methods. Some illustrative examples are included.

A regional climate modeling study of the effect of desert dust on the West African monsoon

Abstract: [1] We investigate the effect of the shortwave radiative forcing of Saharan dust on the West African monsoon with a regional climate model interactively coupled to a dust model. Toward this purpose we intercompare sets of 38 summer monsoon season simulations (1969–2006) with and without dust effects over a domain encompassing most of the African continent and adjacent regions. We find that the main effect of the dust radiative shortwave forcing is to reduce precipitation over the Sahel region. This is in response to cooling over the Sahara, which decreases the meridional gradient of moist static energy and results in a weakening of the monsoon energy pump. The dust effects also cause a strengthening of the southern branch of the African Easterly Jet and a weakening of Tropical Easterly Jet. Over the Sahel the dust forcing causes climate response patterns that are similar to those found during dry years over the Sahel, which suggests that Saharan dust feedbacks might have a role in maintaining drought events over the region. Overall, the inclusion of dust also tends to improve the model simulation of the West African monsoon, as well as African and Tropical Easterly jets. This work focuses on climatic feedback associated to shortwave radiation forcing and should be further completed by the study of dust effect on long-wave radiation.

Long term measurements of sulfur dioxide, nitrogen dioxide, ammonia, nitric acid and ozone in Africa using passive samplers

Abstract: In this paper we present the long term monitoring of ambient gaseous concentrations within the framework of the IDAF (IGAC-DEBITS-AFRICA) program. This study proposes for the first time an analysis of long-term inorganic gas concentrations (1998 to 2007) of SO2, NO2, HNO3, NH3 and O3, determined using passive samplers at seven remote sites in West and Central Africa. Sites are representative of several African ecosystems and are located along a transect from dry savannas-wet savannas-forests with sites at Banizoumbou (Niger), Katibougou and Agoufou (Mali), Djougou (Benin), Lamto (Cote d'Ivoire), Zoetele (Cameroon) and Bomassa (Congo). The strict control of measurement techniques as well as the validation and inter-comparison studies conducted with the IDAF passive samplers assure the quality and accuracy of the measurements. For each type of African ecosystem, the long term data series have been studied to document the levels of surface gaseous concentrations. The seasonal and interannual variability have also been analyzed as a function of emission source variations. We compared the measured West and Central African gas concentrations to results obtained in other parts of the world. Results show that the annual mean concentrations of NO2, NH3, HNO3 measured in dry savannas are higher than those measured in wet savannas and forests that have quite similar concentrations. Annual mean NO2 concentrations vary from 0.9±0.2 in forests to 2.4±0.4 ppb in the dry savannas, NH3 from 3.9±1.4 to 7.4±0.8 ppb and HNO3 from 0.2±0.1 to 0.5±0.2 ppb. Annual mean O3 and SO2 concentrations are lower for all ecosystems and range from 4.0±0.4 to 14.0±2.8 and from 0.3±0.1 to 1.0±0.2 ppb, respectively. A focus on the processes involved in gas emissions from dry savannas is presented in this work, providing explanations for the high concentrations of all gases measured at the three dry savannas sites. At these sites, seasonal concentrations of all gases are higher in the wet season. Conversely, concentrations are higher in the dry season in the wet savannas. In forested regions, we measure no significant difference between wet and dry seasons. This unique database of long term gases concentrations monitoring is available at: http://medias.obs-mip.fr/idaf/.