Contributions of SST anomalies in the Indo-Pacific Oceans to the interannual variability of tropical cyclone genesis frequency over the western North Pacific

AbstractThis study attempts to evaluate quantitatively the contributions of sea surface temperature (SST) anomalies in the Indo-Pacific Oceans to the interannual variability of tropical cyclone (TC) genesis frequency (TCGF) over the western North Pacific (WNP). Three SST factors in the IndoPacific Oceans are found to play key roles in modulating the interannual variability of WNP TCGF. They are summer SST anomaly in the East Indian Ocean (EIO), summer El Nino-Southern Oscillation Modoki index (EMI), and spring SST gradient (SSTG) between the southwestern Pacific and the western Pacific warm pool. Results show that the three factors together can explain 72% of the total variance of WNP TCGF in the typhoon season for the period 1980-2015. Among them, the spring SSTG and the summer EIO contribute predominantly to the interannual variability of TCGF, followed by the summer EMI, with their respective contributions by 39%, 38% and 23%. Further analysis shows that the summer EMI was affected significantly by the...