Is the North Pacific Victoria Mode a Predictor of Winter Rainfall over South China?

Abstract

This study investigates the connection between the North Pacific Victoria mode (VM) during the boreal spring [February–April (FMA)] and the following boreal winter [January–March (JFM)] rainfall over South China (SC). The VM is defined as the second empirical orthogonal function mode (EOF2) of sea surface temperature (SST) anomalies (SSTAs) in the North Pacific poleward of 20°N. It is found that the boreal spring VM has a significant positive correlation with the following winter rainfall over SC. Analyses indicate that a strong positive VM during spring can induce El Niño during the following winter via an air–sea interaction, resulting in the generation of an anomalous anticyclone over the western North Pacific (WNPAC). The anomalous southwesterlies along the southeast coast of East Asia associated with the WNPAC favor an abundant supply of water vapor and anomalous ascending motion over SC. As a result, winter rainfall over SC increases. A linear regression model based on the VM shows that the VM can act as an effective predictor of winter rainfall over SC about 1 year in advance. It also has a higher prediction skill than ENSO in predicting winter rainfall over SC.