Interannual modulation of summer precipitation over North China by the coupled tropical Pacific–Atlantic SST Dipole Mode

Using multi-source reanalysis data, this study examines the relationship between the tropical Pacific–Atlantic SST Dipole Mode (TPA-DM) and summer precipitation in North China (NCSP) on the interannual timescale during the period of 1979–2022. The results show that the TPA-DM, the dominant pattern of interannual variability in the tropical Pacific and Atlantic regions, exhibits a significant negative correlation with NCSP. The positive phase of TPA-DM induces subsidence over the Maritime Continent through a zonal circulation pattern, which initiates a Pacific–Japan-like wave train along the East Asian coast. The circulation anomalies lead to moisture deficits and convergence subsidence over North China, leading to below-normal rainfall. Further analysis reveals that cooler SST in the Southern Tropical Atlantic facilitates the persistence of the TPA-DM by stimulating the anomalous Walker circulation associated with wind–evaporation–SST–convection feedback. 摘要 利用多源再分析数据, 本文研究了1979–2022年期间热带太平洋–大西洋海温偶极子模态 (TPA-DM) 对中国华北地区夏季降水 (NCSP) 年际变化的影响. 结果表明, TPA-DM是热带太平洋和大西洋海温年际变率的主导模态, 与NCSP呈显著的负相关关系 (−0.52) . TPA-DM的正位相海温异常通过纬向环流在海洋性大陆引发异常下沉, 进而在东亚沿海激发出类似太平洋–日本型的波列, 导致华北地区水汽减少和辐合下沉, 从而造成降水异常偏少. 此外, 热带南大西洋的异常冷海温通过激发与风–蒸发–海温–对流反馈机制, 促使异常沃克环流的形成, 从而增强和维持了TPA-DM型海温的增强与维持.