Early and Extreme Warming in the South China Sea During 2015/2016: Role of an Unusual Indian Ocean Dipole Event

The South China Sea (SCS) experienced sea surface temperature that broke historical records in the autumn of 2015. This event cannot be explained by El Nino alone because the SCS usually warms during the El Nino peak and decaying phases. We show that an early anomalous anticyclone (AAC) establishment over the SCS in August contributed to this early warming. Analysis and simple modeling results reveal that such an early AAC establishment could be interpreted as a direct Rossby wave response to a cooling anomaly over the Maritime Continent (MC) and a Kelvin wave response to a heating anomaly over the tropical Indian Ocean (TIO). An unusual Indian Ocean dipole event contributed to the atmospheric heating anomaly over the TIO and made the cooling anomaly shrink to MC region. We should take into consideration the Indian Ocean SST patterns to improve the predictability of extreme East Asian climate.