Major drivers of summer extreme precipitation over the Yangtze River Basin

Utilizing ERA5 reanalysis data, we carried out a series of analyses to investigate the major drivers influencing the interannual variability of summer extreme precipitation over the Yangtze River Basin (YRB) during 1950-2021. We found that both ENSO and IOD have the capability to generate anomalous anticyclones/cyclones over the Western North Pacific (WNPAC/WNPC), which in turn can enhance or diminish water vapor transport, leading to an increase or decrease in summer extreme precipitation over the YRB. However, the impact of negative ENSO-IOD forcings is generally weaker than that of positive forcings. The persistence of the abnormal tropospheric WNPAC/WNPC is primarily driven by local thermodynamic forcing and feedback from the Indian Ocean Basin Warming (IOBW). It is noteworthy that only strong ENSO events can trigger the anomalous IOBW, resulting in more pronounced responses in summer extremes. Notably, the negative ENSO-IOD phases yield non-linear outcomes, thus offering less robustness for the predictability of summer extremes over the YRB. This study provides valuable insights into the interannual variability of summer extreme precipitation in the YRB, highlighting the key predictors and physical mechanisms responsible for these variations.