摘要
Recent findings indicate that rainfall variability over West Africa is characterized by more positive anomalies in the last four decades.The authors demonstrate that the recent interannual rainfall variability is linked to an air–sea phenomenon that occurs in the tropical Atlantic and eastern Pacific Ocean,and then propose the Trans-Atlantic-Pacific Ocean Dipole(TAPOD)index as a measure for this tropical ocean phenomenon,which is found to be closely correlated with the West African summer rainfall anomalies.Using observational and reanalysis datasets,composite analysis suggests that enhanced precipitation in West Africa is associated with the positive phase of the TAPOD,which is characterized by warm sea surface temperature anomalies(SSTAs)in the tropical Atlantic and cool SSTAs in the tropical eastern Pacific Ocean.During the positive phase of the TAPOD,there are significant westerly anomalies over the tropical Atlantic Ocean,which drives anomalous water vapor convergence over West Africa,leading to enhanced precipitation in the region.
本研究基于资料统计分析发现西非地区夏季降水与热带大西洋和太平洋海温异常存在紧密的关系;在此基础上提出可表征热带大西洋-太平洋海温异常结构特征的跨大西洋-太平洋偶极型(TAPOD)指数,该指数与西非夏季降水异常存在显著正相关。合成分析表明,当TAPOD指数为正位相时,热带大西洋地区海温为正异常、热带东太平洋海温为负异常,此时热带大西洋地区存在着显著的西风异常,西非地区则存在水汽净幅合异常,有利于该地区夏季降水的异常偏多;反之亦然。
基金
jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)[grant number XDA19030403]
the National Natural Science Foundation of China [grant numbers 41575095 and41661144032]
the CAS ‘Belt and Road Initiatives’ Program on International Cooperation [grant number134111KYSB20160010]
Victor Nnamdi DIKE acknowledges the support of a CAS-TWAS President Fellowship
