气候变化领域集成服务门户(CCPortal): Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation

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DOI	10.1007/s00382-021-05696-x
	Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation
	Zhang Q.; Berntell E.; Li Q.; Ljungqvist F.C.
发表日期	2021
ISSN	0930-7575
起始页码	2183
结束页码	2201
英文摘要	There is a well-known mode of rainfall variability associating opposite hydrological conditions over the Sahel region and the Gulf of Guinea, forming a dipole pattern. Previous meteorological observations show that the dipole pattern varies at interannual timescales. Using an EC-Earth climate model simulation for last millennium (850–1850 CE), we investigate the rainfall variability in West Africa over longer timescales. The 1000-year-long simulation data show that this rainfall dipole presents at decadal to multidecadal and centennial variability and long-term trend. Using the singular value decomposition (SVD) analysis, we identified that the rainfall dipole present in the first SVD mode with 60% explained variance and associated with the variabilities in tropical Atlantic sea surface temperature (SST). The second SVD mode shows a monopole rainfall variability pattern centred over the Sahel, associated with the extra-tropical Atlantic SST variability. We conclude that the rainfall dipole-like pattern is a natural variability mode originated from the local ocean–atmosphere-land coupling in the tropical Atlantic basin. The warm SST anomalies in the equatorial Atlantic Ocean favour an anomalous low pressure at the tropics. This low pressure weakens the meridional pressure gradient between the Saharan Heat Low and the tropical Atlantic. It leads to anomalous northeasterly, reduces the southwesterly moisture flux into the Sahel and confines the Gulf of Guinea's moisture convergence. The influence from extra-tropical climate variability, such as Atlantic multidecadal oscillation, tends to modify the rainfall dipole pattern to a monopole pattern from the Gulf of Guinea to Sahara through influencing the Sahara heat low. External forcing—such as orbital forcing, solar radiation, volcanic and land-use—can amplify/dampen the dipole mode through thermal forcing and atmosphere dynamical feedback. © 2021, The Author(s).
英文关键词	Atlantic multidecadal oscillation; Decadal to multidecadal variability; EC-Earth; Last millennium; Tropical Atlantic variability; West Africa rainfall dipole
来源期刊	Climate Dynamics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/183545
作者单位	Department of Physical Geography, Stockholm University, Stockholm, Sweden; Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden; Department of History, Stockholm University, Stockholm, Sweden; Swedish Collegium for Advanced Study, Uppsala, Sweden
推荐引用方式 GB/T 7714	Zhang Q.,Berntell E.,Li Q.,et al. Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation[J],2021.
APA	Zhang Q.,Berntell E.,Li Q.,&Ljungqvist F.C..(2021).Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation.Climate Dynamics.
MLA	Zhang Q.,et al."Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation".Climate Dynamics (2021).