Enhancement of the relationship between spring extreme precipitation over Southwest China and preceding winter sea surface temperature anomalies over the South Indian Ocean after the late 1980s

Spring extreme precipitation (SEP) significantly disturbs spring ploughing over Southwest China (SWC), bringing challenges for agricultural activities and production over the region. This study investigates the interannual relationship between SWC SEP and sea surface temperature (SST) in preceding winter, from a perspective of prediction. It is found that the dominate mode of SWC SEP interannual variability mainly reflects the variability over the eastern part. The variability of eastern SWC SEP has an enhanced connection with a dipole SST pattern over the South Indian Ocean in preceding winter after the late 1980s. Under the warmer SST background after the late 1980s, the South Indian Ocean dipole SST pattern can lead to significant convection activity over tropical central and western Indian Ocean. The tropical diabatic heating associated with enhanced convection can strengthen the western North Pacific anticyclone, which transports more water vapour to eastern SWC and induces stronger moisture convergence there, providing favourable moisture condition for the SEP occurrence. In addition, the dipole SST pattern can strengthen upward motion over eastern SWC through exiting a meridional circulation, providing a favourable dynamic condition for the SEP occurrence over there. In contrast, under the colder SST background before the late 1980s, the dipole SST pattern-related convection and atmospheric circulation anomalies are weak over the Indo-Pacific region. Therefore, the relationship of the dipole SST pattern with SEP over eastern SWC is weak before the late 1980s. The SST signals with one-season leading could provide valuable source for seasonal prediction of eastern SWC SEP variability after the late 1980s.