Increased knowledge of future changes in rainfall variability is needed to reduce vulnerability to potential impacts of global warming, especially in highly vulnerable regions like West Africa. While changes in mean and extreme rainfall have been studied extensively, rainfall variability has received less attention, despite its importance. In this study, future changes in West African summer monsoon (WASM) rainfall variability were investigated using data from two regional climate models that participated in the Coordinated Regional Climate Downscaling Experiment (CORDEX). The daily rainfall data were band-pass filtered to isolate variability at a wide range of timescales. Under global warming, WASM rainfall variability is projected to increase by about 10–28% over the entire region and is remarkably robust over a wide range of timescales. We found that changes in mean rainfall significantly explain the majority of intermodel spread in projected WASM rainfall variability. The role of increased atmospheric moisture is examined by estimating the change due to an idealized local thermodynamic enhancement. Analysis reveals that increased atmospheric moisture with respect to warming following the Clausius–Clapeyron relationship can explain the majority of the projected changes in rainfall variability at all timescales.

为了减少对全球变暖潜在影响的脆弱性，尤其是在西非等高度脆弱的地区，需要更多地了解降雨变化的未来变化。尽管已经对平均雨量和极端雨量的变化进行了广泛的研究，但雨量变异性尽管很重要，但却很少受到关注。在这项研究中，西非夏季风（WASM）降雨变异性的未来变化是使用参与协调的区域气候缩减试验（CORDEX）的两个区域气候模型的数据进行调查的。对每日降雨量数据进行了带通滤波，以隔离大范围时间范围内的变化。在全球变暖的情况下，预计WASM的降雨量变化率将在整个区域内增加约10％至28％，并且在很宽的时间范围内都将表现出明显的稳健性。我们发现，平均降水量的变化显着解释了预计的WASM降水变化中大部分模型间的传播。通过估计由于理想化的局部热力学增强而引起的变化，来检查增加大气湿度的作用。分析表明，遵循克劳修斯-克拉珀龙关系，相对于变暖而言，大气湿度的增加可以解释所有时间尺度上降雨变化的大部分预测变化。