Convective-permitting ensemble simulations are used to understand the roles of thermodynamic and dynamic processes in changing intense storms over the West African Sahel due to increases in atmospheric greenhouse gas concentrations. Ensemble simulations with 16 members represent recent August conditions during the height of the boreal summer monsoon season over the Sahel. They are compared with 5 Future-Warming ensemble simulations with increased greenhouse gas concentrations under the late-21st -century high-emission SSP5-8.5 scenario and initial/boundary conditions from the Current-Climate data plus the multi-model mean anomalies derived from CMIP6 experiments. The Current-Climate simulations reproduce observed precipitation and environmental conditions over the Sahel well. The frequency of heavy rainfall events with 24-hr rainfall > 77 mm (the 99.9th percentile) increases by \(\ge\)38.2% in the Future-Warming simulations. While the low- to mid-level vertical wind shear increases in the Future-Warming simulations, we find no significant correlations between the environmental shear strength and peak storm rain rates. In contrast, lower (middle) tropospheric moisture and temperature are correlated (anticorrelated) with peak rain rates and/or the maximum updraft velocity of intense events, consistent with significant correlations between the increased atmospheric instability and storm intensity. Thus, thermodynamic processes and not dynamical (shear-related) processes dominate the rainfall intensification over the Sahel in the simulations. Nevertheless, the enhanced shear strength is associated with larger rain-shield areas and propagation speeds of intense storms in Future-Warming. Wind shear strength is also correlated with pre-storm atmospheric instability, which grows less/more under strong/weak shear with greenhouse gas increases and is relevant for sub/super Clausius-Clapeyron scaling of precipitation.

允许对流的集合模拟用于了解由于大气温室气体浓度增加而导致西非萨赫勒地区强烈风暴变化的热力学和动力学过程的作用。由 16 名成员组成的集合模拟代表了最近 8 月萨赫勒地区北方夏季季风季节高峰期的情况。将它们与 21 世纪末高排放 SSP5-8.5 情景下温室气体浓度增加的 5 个未来变暖集合模拟以及当前气候数据的初始/边界条件以及源自 CMIP6 的多模型平均异常进行比较实验。当前气候模拟再现了萨赫勒地区观测到的降水和环境条件。在未来变暖模拟中，24 小时降雨量 > 77 毫米（第 99.9 个百分位数）的强降雨事件频率增加了38.2 % 。虽然未来变暖模拟中低至中层垂直风切变有所增加，但我们发现环境切变强度与峰值暴雨率之间没有显着相关性。相反，对流层下部（中层）湿度和温度与峰值降雨率和/或强烈事件的最大上升气流速度相关（反相关），这与大气不稳定性增加和风暴强度之间的显着相关性一致。因此，在模拟中，热力学过程而非动力（剪切相关）过程主导了萨赫勒地区的降雨强度。然而，剪切强度的增强与未来变暖期间更大的防雨面积和强烈风暴的传播速度有关。风切变强度还与暴风雨前的大气不稳定性相关，随着温室气体的增加，在强/弱切变下大气不稳定性会减少/增加，并且与降水的亚/超级克劳修斯-克拉佩龙尺度相关。