A COMPARATIVE STUDY OF SEASONAL AND QUIETTIME foF2 DIURNAL VARIATION AT DAKAR AND OUAGADOUGOU STATIONS DURING SOLAR MINIMUM AND MAXIMUM FOR SOLAR CYCLES 21-22

A statistical study of quiet time foF2 diurnal variation of two West Africa stations (Dakar and Ouagadougou) is examined through seasons and during solar minimum and maximum phases. It is shown that during solar minimum and for all seasons both stations foF2 exhibit the same variability with more and less deep trough between 1200 LT and 1400 LT. foF2 profiles are afternoon predominance profiles except during winter and for Dakar station where the profile is morning predominance peak. During solar maximum, foF2 profiles show different behavior only for spring and summer where Dakar foF2 profiles are plateau profile and dome profile, respectively. For these seasons Ouagadougou profiles are morning predominance profile and noon bite out profile, respectively. At daytime there is more ionosphere at Dakar station than Ouagadougou at all seasons and for the solar cycle phases involved

Competitiveness Level of Photovoltaic Solar Systems in Ouagadougou (Burkina Faso): Study Based on the Domestic Electric Meters Calibration

The mean cost price of electricity in Burkina Faso at the end of the last quarter of 2012 was 158 FCFA/kWh for a country where more than 46% of the population lives below the national poverty threshold. To look for solution to that problem, the resort to photovoltaic solar energy is justified for that country. The purpose of this study is to promote the integration of both technical and economical surveys in solar energy preliminary projects in Ouagadougou. To reach that, investigations were carried out in some households and attention was paid from the calibration of the domestic electric meters. Energy demands collected within each household allow us to design a corresponding solar kit through optimization rules. An estimate was edited and financial viability study for each household was also carried out thereafter. In this study, only households using the national electricity network calibration meter on their disadvantage favorably answered to all financial indicators and appear as the only one that could profit from such project. This work is helpful to note that photovoltaic solar energy still stays at a primitive level of competitiveness compared to conventional energy resources for small systems in Ouagadougou

High-resolution rainfall maps from commercial microwave links for a data-scarce region in West Africa

We present high-resolution rainfall maps from commercial microwave link (CML) data in the city of Ouagadougou, Burkina Faso. Rainfall was quantified based on data from 100 CMLs along unique paths and interpolated to achieve rainfall maps with a 5-min temporal and 0.55-km spatial resolution for the monsoon season of 2020. Established processing methods were combined with newly developed filtering methods, minimizing the loss of data availability. The rainfall maps were analyzed qualitatively both at a 5-min and aggregated daily scales. We observed high spatiotemporal variability on the 5-min scale that cannot be captured with any existing measurement infrastructure in West Africa. For the quantitative evaluation, only one rain gauge with a daily resolution was available. Comparing the gauge data with the corresponding CML rainfall map pixel showed a high agreement, with a Pearson correlation coefficient > 0.95 and an underestimation of the CML rainfall maps of ∼10%. Because the CMLs closest to the gauge have the largest influence on the map pixel at the gauge location, we thinned out the CML network around the rain gauge synthetically in several steps and repeated the interpolation. The performance of these rainfall maps dropped only when a radius of 5 km was reached and approximately one-half of all CMLs were removed. We further compared ERA5 and GPM IMERG data with the rain gauge and found that they had much lower correlation than data from the CML rainfall maps. This clearly highlights the large benefit that CML data can provide in the data-scarce but densely populated African cities

Comparaison et détermination des dispositifs de stockage appropriés pour un système photovoltaïque autonome en zone sahélienne

Dans le contexte de changement climatique actuel, les énergies renouvelables en particulier l’énergie solaire photovoltaïque constituent une bonne alternative aux énergies conventionnelles. L’énergie solaire est une énergie non polluante, disponible sur l’ensemble du globe et aussi la ressource la mieux partagée sur terre. Toutefois, l’alternance jour/nuit provoquée par la rotation de la terre et les aléas climatiques causés par les orages et les passages nuageux limitent considérablement son utilisation de façon permanente. Pour pallier cette insuffisance et assurer la continuité du service dans les systèmes photovoltaïques (PV), l’utilisation de dispositif de stockage d’énergie est nécessaire. Il existe différents types de stockage dont certains déjà utilisés et d'autres en développement. Dans cet article, nous proposons d’examiner les principales caractéristiques des différentes techniques de stockage d'électricité et leur domaine d'application dans les systèmes PV en zone sahélienne (stockage permanent à long ou à court terme, puissance maximale requise, etc.). Pour permettre le choix des dispositifs de stockage appropriés, nous avons développé une approche caractérisée par l’indice de performance que nous avons implémenté en utilisant des matrices élémentaires de décision et des matrices globales de décision. Les résultats obtenus montrent que la méthode proposée permet de déterminer les dispositifs appropriés pour chaque type d’application et selon les besoins de la charge

Influence des aérosols sur la composition à l’équilibre d’un plasma d’air

La mousson et l’harmattan sont les principales dynamiques atmosphériques qui gouvernent le transport et le dépôt des aérosols en Afrique de l’Ouest. Ces aérosols proviennent du désert et des feux de biomasses et sont essentiellement composés d’oxydes de silicium, de calcium, de fer, d’aluminium et d’éléments carbonés issus de la biomasse. Ainsi, lorsque les disjoncteurs à air doivent fonctionner dans un environnement pollué par ces aérosols, ils peuvent avoir des comportements anormaux et des échecs de coupures. Ce travail porte sur l’influence des aérosols sur la composition chimique de plasma d’air à la pression atmosphérique et à l’équilibre thermodynamique local (E.T.L) dans une gamme de température allant de 4000 K à 20000 K. Nous utilisons la méthode de minimisation de l’énergie libre de Gibbs pour déterminer la composition du plasma. Les résultats obtenus montrent que la densité électronique augmente avec le pourcentage d’aérosols dans le plasma pour une température inférieure à 12000 K. Cela pourrait conduire à une augmentation de la conductivité électrique du plasma à basse température

Towards innovative solutions for monitoring precipitation in poorly instrumented regions: real-time system for collecting power levels of microwave links of mobile phone operators for rainfall quantification in Burkina Faso

Since the 1990s, mobile telecommunication networks have gradually become denser around the world. Nowadays, large parts of their backhaul network consist of commercial microwave links (CMLs). Since CML signals are attenuated by rainfall, the exploitation of records of this attenuation is an innovative and an inexpensive solution for precipitation monitoring purposes. Performance data from mobile operators’ networks are crucial for the implementation of this technology. Therefore, a real-time system for collecting and storing CML power levels from the mobile phone operator “Telecel Faso” in Burkina Faso has been implemented. This new acquisition system, which uses the Simple Network Management Protocol (SNMP), can simultaneously record the transmitted and received power levels from all the CMLs to which it has access, with a time resolution of one minute. Installed at “Laboratoire des Matériaux et Environnement de l’Université Joseph KI-ZERBO (Burkina Faso)”, this acquisition system is dynamic and has gradually grown from eight, in 2019, to more than 1000 radio links of Telecel Faso’s network in 2021. The system covers the capital Ouagadougou and the main cities of Burkina Faso (Bobo Dioulasso, Ouahigouya, Koudougou, and Kaya) as well as the axes connecting Ouagadougou to these citie

Effect of Initial Size and Shape Importance on Masse Transfer during Convective Drying

International audienc

Extreme Rainfall in Southern Burkina Faso, West Africa: Trends and Links to Atlantic Sea Surface Temperature

Understanding the space-time variations of extreme rainfall plays an important role in the management of water-related disasters in Sahel countries. This study investigates temporal changes in rainfall characteristics and explores the link between Atlantic Sea surface temperature and extreme rainfall in the southern part of Burkina Faso. We find substantial spatial heterogeneity in rainfall trends across the study area. In contrast to national and supra-national studies that found predominantly increasing trends in extreme rainfall, we detect more downward than upward trends, particularly for indices representing extreme rainfall. This difference is presumably a consequence of the high spatial variability in rainfall trends that can only be detected with sufficiently dense climate networks. We use the Poisson-General Pareto (Poisson-GP) distribution to quantify the frequency and intensity of extreme rainfall. Our comparison of the traditional, stationary Poisson-GP model with the nonstationary version where rainfall depends on Atlantic SST shows that the nonstationary model outperforms the traditional approach. This finding suggests that the assumption of stationary nature must be considered with care when modeling the frequency and intensity of extreme rainfall in the study area. Overall, our results suggest that the recent increase in flood disasters in Burkina Faso is rather caused by land use and land cover changes and population and urban growth and not by increasing rainfall extremes

Soil-Water Characteristic Curve Modeling at Low Water Content: Empirical and Semi-Empirical Approaches

International audienceIn this paper, we evaluate the performance of the most widely used semi-empirical models (van Genuchten (1980), Fayer and Simmons (1995) and Fredlund and Xing (1994)) and, an empirical model, the Modified Kovacs (MK) model for the determination of soil-water characteristic curve at the low water contents of two horizons of a soil from Burkina Faso. Combining terms from capillary state and adsorbed state of soil water gives a physical basis for the Modified Kovacs model. Our study confirms that the use of semi-empirical models requires somewhat large dataset covering the entire range of water content while the empirical model MK requires only basic geotechnical properties of soil and a few experimental points to adjust the parameters m and ac of the model. It appears that the MK model, by its simplicity and lower cost for the acquisition of experimental data, is the most appropriate