Sahel rainfall and decadal to multi-decadal sea surface temperature variability
Sahel rainfall and decadal to multi-decadal sea surface temperature variability
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DOI：
10.1007/s00382-010-0867-2
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发表时间：
2011-08-01
期刊：
影响因子：
4.6
通讯作者：
Bader, Juergen
中科院分区：
文献类型：
--
作者：
Mohino, Elsa;Janicot, Serge;Bader, Juergen
二十世纪萨赫勒地区十年间降雨量的变化主要是由海面温度（SST）驱动的。与此同时，海表温度呈现出明显的长期全球变暖（GW）趋势。叠加在这种长期趋势上的年代际和多年代际变化模式可以被观察到，例如大西洋多层振荡（AMO）和年代际太平洋振荡（IPO）。使用大气环流模型，我们研究了每个成分对萨赫勒降水变化的相对贡献。为了考虑与使用不同海表温度数据集相关的不确定性，我们使用 HadISST1 和 ERSSTv3 重建集进行实验。模拟显示，所有三个海温信号对西非都有重大影响：GW 和 IPO 的正相位导致萨赫勒地区干旱，而 AMO 正相位则增加萨赫勒降雨量。热带海温变暖是GW影响萨赫勒降雨的主要原因。关于AMO，异常降水的模式是由大西洋和地中海盆地的海温确定的。反过来，热带海温异常控制了 IPO 部分对西非的影响。我们的研究结果表明，萨赫勒降雨的低频演变可以解释为三个因素的竞争：GW、AMO 和 IPO 的影响。根据这一解释，我们的结果表明，20 世纪 80 年代由海温驱动的萨赫勒干旱有 50% 是由 AMO 的负相位变化来解释的，而 GW 的贡献为 10%。此外，近年来萨赫勒地区降雨量的部分恢复主要是由AMO推动的。
Decadal Sahelian rainfall variability was mainly driven by sea surface temperatures (SSTs) during the twentieth century. At the same time SSTs showed a marked long-term global warming (GW) trend. Superimposed on this long-term trend decadal and multi-decadal variability patterns are observed like the Atlantic Multidecadal Oscillation (AMO) and the inter-decadal Pacific Oscillation (IPO). Using an atmospheric general circulation model we investigate the relative contribution of each component to the Sahelian precipitation variability. To take into account the uncertainty related to the use of different SST data sets, we perform the experiments using HadISST1 and ERSSTv3 reconstructed sets. The simulations show that all three SST signals have a significant impact over West Africa: the positive phases of the GW and the IPO lead to drought over the Sahel, while a positive AMO enhances Sahel rainfall. The tropical SST warming is the main cause for the GW impact on Sahel rainfall. Regarding the AMO, the pattern of anomalous precipitation is established by the SSTs in the Atlantic and Mediterranean basins. In turn, the tropical SST anomalies control the impact of the IPO component on West Africa. Our results suggest that the low-frequency evolution of Sahel rainfall can be interpreted as the competition of three factors: the effect of the GW, the AMO and the IPO. Following this interpretation, our results show that 50% of the SST-driven Sahel drought in the 1980s is explained by the change to a negative phase of the AMO, and that the GW contribution was 10%. In addition, the partial recovery of Sahel rainfall in recent years was mainly driven by the AMO.