Variabilite Du Climat Au Sahel Central Depuis 1950: Essais D’Analyses Statistiques Des Relations Entre Precipitations, Vent et Visibilite Horizontale Au Se-Niger (original) (raw)

Abstract

ABSTRACT Maine-Soroa and N’Guigmi are located in SE Niger, in the Lake Chad basin. Some signal analysis methods used in hydrolgy were tested on the rainfalls, the wind speed and the horizontal visibility data. Using a local polynomial fitting reveals a long-term trend change of regim in the late 1960s. The Continuous Wavelets Analysis reveals some coherents frequency modes at seasonnal and quasidecadal scales, but the rainfall-visibility and the wind speed-visibiliy relationship are more complex. Hysteresis and cross-correlation function of mean daily regims were used for study the intra-seasonal and seasonal scales. We notice that, even if the rainfall increases the visibility, this one doesn’t modulate instantaneously the regional dust contributions. On the contrary, these contributions are linked to the wind speed.

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