Variabilité de la dynamique éolienne au Sahel : caractéristiques des vents et de la visibilité horizontale entre 1950 et 1989 à Maïne-Soroa (Niger Oriental). Aeolian dynamics variability between 1950 and 1989 in the Sahel: wind characteristics and horizontal visibility at Maïné-Soroa (eastern Niger)
Résumé
Au Sahel, les études sur le changement climatique portent principalement sur les précipitations. Pourtant, ces précipitations sont peu représentatives des conditions locales permanentes car elles sont concentrées sur une partie de l'année (saison des pluies) et ne concernent que quelques dizaines de jours seulement. Au contraire les jours sans vent sont rares. Cette étude a donc pour objectif de savoir si le changement climatique peut être appréhendé à partir des paramètres du vent. Elle concerne la station de Maïné-Soroa (Niger oriental) entre 1950 et 1989. Elle porte sur les chroniques de 3 mesures journalières instantanées (à 6h, 12h et 18h) de la vitesse, de la direction du vent et de la visibilité horizontale liée aux poussières transportées par le vent. Les variations de vitesse et direction du vent permettent aisément de retrouver le changement majeur de la période 1967-1972 aussi bien que les fortes anomalies, tant aride (1984-1986) qu'humide (1951- 1954). On observe une diminution très importante de la visibilité horizontale après 1969.
Studies on climate change in the Sahel mainly concerns precipitations. However, these precipitations are not very representative of the permanent local conditions because they are concentrated during a part of the year (rainy season) and only during a few tens of days. On the contrary, the days without wind are rare. The aim of this study is thus to know if the climate change can be appraised by an analysis of wind parameters. The study concerns the meteorological station of Maïné- Soroa (Eastern Niger) between 1950 and 1989. It relates to the high frequency chronicle (3 measurements each day at 6:00, 12:00 and 18:00) of the speed and direction of the wind and the horizontal visibility related to the dust transported by the wind. The variations of speed and direction show the well-known major change during the period 1967-1972 as well as the strong anomalies, arid (1984-1986) and wet (1951-1954). Since 1969, we also observe a very important reduction in the horizontal visibility.
Studies on climate change in the Sahel mainly concerns precipitations. However, these precipitations are not very representative of the permanent local conditions because they are concentrated during a part of the year (rainy season) and only during a few tens of days. On the contrary, the days without wind are rare. The aim of this study is thus to know if the climate change can be appraised by an analysis of wind parameters. The study concerns the meteorological station of Maïné- Soroa (Eastern Niger) between 1950 and 1989. It relates to the high frequency chronicle (3 measurements each day at 6:00, 12:00 and 18:00) of the speed and direction of the wind and the horizontal visibility related to the dust transported by the wind. The variations of speed and direction show the well-known major change during the period 1967-1972 as well as the strong anomalies, arid (1984-1986) and wet (1951-1954). Since 1969, we also observe a very important reduction in the horizontal visibility.
Domaines
Sciences de la Terre| Origine | Accord explicite pour ce dépôt |
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