Different Responses of Sea Surface Temperature in the South China Sea to Various El Niño Events during Boreal Autumn

This study investigates variations of sea surface temperature (SST) anomalies in the South China Sea (SCS) during developing autumn of various El Niño events. The warm SCS SST anomalies are observed in the SCS for canonical El Niño and El Niño Modoki I, whereas the cold SST anomalies are found for El Niño Modoki II. The ocean heat budget analyses show that the latent heat flux change induced by various types of El Niño is a major contributor to the SCS SST variations. An anomalous anticyclone resides near the Philippine Sea for canonical El Niño and El Niño Modoki I, which induces the southerly wind anomalies over the SCS and thus weakens the climatological northeasterly in boreal autumn. The weakened surface wind speed reduces heat loss from the ocean, leading to a warmer state in the SCS. For El Niño Modoki II, the anomalous anticyclone shifts westward to the west of the SCS, and thus the northeasterly wind anomalies appear in the SCS. Such northeasterly anomalies combined with the climatological northeasterly monsoon increase the wind speed, and make the ocean release more latent heat and thus result in the cooling SCS. The anomalous anticyclone associated with three types of El Niño can intensify the shortwave radiation. The increases of the shortwave radiation can also contribute to the SCS warming together with the latent heat flux for canonical El Niño and El Niño Modoki I. However, the magnitude of the latent heat flux is larger than that of the shortwave radiation flux for El Niño Modoki II, and thus the SCS tends to be cool.