The enhanced relationship between Southern China winter rainfall and warm pool ocean heat content

A decadal change on relationship between winter rainfall over Southern China (SCWR) and Western Pacific warm pool heat content (WPHC) was detected by a sliding correlation analysis. The decadal turning point occurred around 1993. Before 1993, the relationship between SCWR and WPHC was quite weak with a correlation coefficient of -0.17. During this epoch, the WPHC-related anomalous troposphere circulation, sea surface temperature (SSTA) and outgoing longwave radiation (OLRA) were mainly confined to the Pacific Ocean. Therefore, the corresponding climate system anomalies cannot influence SCWR. However, after 1993, the relationship between SCWR and WPHC became significant and reached a correlation coefficient of -0.81. The troposphere circulation anomalies along with the SSTA and OLRA pattern that were associated with WPHC during this epoch significantly shifted northwestward and intensified, resulting in a direct impact on SCWR. A possible mechanism was put forth to explain the decadal enhanced relation between SCWR and WPHC. In the context of the increased and northwestward-shifted climatological maximum WPHC, the concurrent intensified and northwestward-shifted SST and atmospheric circulation anomaly pattern contributes to the decadal enhanced relation between SCWR andWPHC. On one hand, because of the increased and northwestward-shifted maximum sea surface temperature, the convection became more sensitive to the SSTA over Indian Ocean and Maritime Continent, thus dragged the Philippines anticyclonic/cyclonic anomaly northwestward via Kevin wave and Rossby wave response, which can directly affect SCWR. On the other hand, the increased and northwestward-shifted SSTA anchored the convection anomalies in South China Sea (SCS) and Maritime Continent, impacting the SCWR via anomalous descending/ascending motion of the anomalous local meridional cell.