Program

Rainfall anomalies over southern China are found to be asymmetricly influenced by the Indian Ocean Dipole (IOD), with a far stronger influence from positive IOD (pIOD) events. A greater convection anomaly and an equivalent-barotropic Rossby wave train response occurs during pIOD events than during negative IOD (nIOD) events. Over the Bay of Bengal (BOB) and South China Sea (SCS), an associated low-level anomalous anticyclone strengthens the southwesterlies during boreal fall (September, October and November, SON), when a pIOD matures. The increased moisture flux gives rise to the anomalously high rainfall over southern China. During its developing phase (boreal summer, June, July, and August, JJA), the influence of a pIOD event on the contemporaneous rainfall over southern China is weak, but a JJA pIOD index is highly correlated with fall rainfall. Therefore, this index can serve as a potential predictor for variations of boreal fall rainfall over southern China.