This study investigates spatial and temporal features of the West African Summer Monsoon (WASM) and its relation to the Sea Surface Temperature Anomaly (SSTA). The variability of the WASM from June to September was analyzed during the period 1960-2013, with methods including EOF analysis of the precipitation anomaly and SSTA and the associated large scale circulation pattern. The result from the first EOF-Mode of the precipitation anomaly which has the highest positive loadings over the region shows that during the summer, the precipitation anomalies are positives in the Sahel and the Sahara. And negative anomaly over the forests of the Congo Basin. Wet (dry) years are: 1961, 1962, 1964, 1965, 1994, 1999, 2003, 2010 and 2012 (1972, 1973, 1982, 1983, 1984, 1987, 1990, and 2002). The first EOF- mode of the Atlantic SSTA shows that between June-September, there is negative SSTA in the South Atlantic and positives SSTA in the rest of the ocean with the highest values (up to 0.8) toward the center of the Ocean. The years where the SST is low (high) are: 1961, 1964, 1965, 1967, 1968, 1970, 1976, 1982 and 1992 (1987, 1998, 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011 and 2013). Further analyses were done including: composite analysis, student t-test, correlation analyses and also the variation of WASM based on the evolution of the West African Summer Monsoon Index. Then the years of weak and strong monsoon were identified. The results show that during years of strong monsoon the heavier precipitation are recorded compare to years of weak monsoon. Same results for the years with low SST over the Atlantic. The correlation maps obtained and the student t-text display for the first three EOF-modes the different key areas in the Atlantic Ocean which have by their surface temperature significant impact on the West African climate.
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