Temporal/spatial distribution of rainfall and the associated circulation anomalies over West Africa
2016
Koumare, I. (Nanjing Univ. of Information Science and Technology (China). Coll. of International Education)
The most important climate variable over West Africa is rainfall, where many sectors of the economy depend on water resources. In this study we investigate the temporal/spatial features of rainfall and the associated circulation anomalies over West Africa. The spatial and temporal distribution of Jun-Sept (JJAS or wet) seasonal rainfall over West Africa was analyzed during the period 1960-2009, inclusive. Empirical Orthogonal Functions (EOF) was used and the associated large scale circulation patterns analyzed. The result from EOF analysis shows that the spatial distribution of rainfall during wet season is relatively uniform (EOFI), showing positive loadings most parts of the study region, except southeastern part. The wet (dry) years of PC1 were identified as; 1961, 1962, 1964, 1965, 1967, 1988, 1994, 1999, and 2003 (1972, 1973, 1982, 1983, 1984, 1987, 1990, and 2002). Analysis of the wet and dry years with respect to the different variables including wind, velocity potential/divergence (convergence) shows that the wet (dry) years were associated with convergence (divergence) in the lower troposphere, (at 850 hpa) and divergence (convergence) at the upper level (200 hpa). This suggests rising (sinking) motion, especially over the study area. The study region is dominated by westerly and southwesterly wind anomalies vectors, especially during wet years at 650 hpa and northeaster lies during dry years at 850 hpa.
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