Precipitation patterns over West Africa display a broad range of timescales, from the intraseasonal to decadal timescales, as well as multidecadal shifts. Here we investigate the dominant patterns of the July to September precipitation over the region and the related ocean-atmosphere anomalies during the satellite-era from 1983 to 2017. Using extended empirical orthogonal function analysis of an ensemble of nine precipitation datasets, we identify two dominant modes that together account for about 33% of the variance. The Sahel mode displays spatially coherent increases in precipitation over much of West Africa and a decrease at the Guinea Coast, and is closely reproduced by linear trend analysis. Linear trends explain 25–53% of the Sahel variance from the drier mid-1980s to the wetter mid-1990s. The Guinea Coast mode displays robust precipitation anomalies south of the Sahel, with strong interannual variability and a statistically non-significant trend. The Sahel mode is associated with a northerly displacement of the Inter-Tropical Convergence Zone (ITCZ), warm North Atlantic with cold blob in the subpolar gyre region, warm Mediterranean Sea, warm tropical southwest Indian Ocean and negative Pacific decadal variability pattern. The Atlantic Niño leads the Guinea Coast mode by two months. Both Sahel and Guinea Coast modes are substantially influenced by the interactions between meridional (displacements of the ITCZ) and zonal (variations of the Walker Circulation) atmospheric circulations. The southerly displacement of the ITCZ, convection, upper-level divergence and surface convergence in the equatorial Atlantic associated with the Guinea Coast mode is horizontally compensated by strong surface divergence and upper-level convergence over the equatorial Pacific where anomalous cooling prevails, implying a strong role for the Walker Circulation during this period.

西非的降水模式显示了广泛的时间尺度，从季节内到年代际尺度，以及多年代际变化。在这里，我们调查了1983年至2017年卫星时代该地区7月至9月降水的主要模式以及相关的海洋-大气异常。使用扩展的经验正交函数分析，对9个降水数据集的集合，我们确定了两个主要的模式合起来占方差的33％。萨赫勒模式在西非大部分地区显示降水在空间上连贯的增长，而在几内亚海岸则有所下降，并且通过线性趋势分析得到了密切的再现。从1980年代中期至1990年代中期，线性趋势解释了萨赫勒地区25-53％的变化。几内亚海岸模式显示出萨赫勒以南的强降水异常，年际变化强烈，且趋势上无统计学意义。萨赫勒模式与热带辐合带（ITCZ）的北移，北极温暖的北大西洋，副极回旋区的冷滴，温暖的地中海，热带的西南印度洋和太平洋的年代际变率负型有关。AtlanticNiño领先几内亚海岸模式两个月。萨赫勒和几内亚海岸模式都受到子午（ITCZ的位移）和纬向（沃克环流的变化）大气环流之间相互作用的影响。ITCZ向南移动，对流，