Interannual and interdecadal variations of tropical cyclone activity in the South China Sea

This study attempts to identify the factors affecting annual tropical cyclone (TC) activity in the South China Sea (SCS) using data during the period 1965-2005. The results indicate that the total number of TCs and number of TCs entering the SCS from the Western North Pacific are below normal in El Niño events but above normal during La Niña events. However, for TCs formed inside the SCS, the difference in numbers between the two phases of the El Niño-Southern Oscillation (ENSO) is not as obvious. In addition, the positive phase of the Pacific Decadal Oscillation (PDO) generally favours less TCs in all categories, while the negative PDO phase favours more. These results may be explained by the fact that the ENSO and the PDO affect TC behaviour through altering the conditions in the WNP to be favourable or unfavourable for TC genesis and movement into the SCS.