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

摘要

This study investigates variations of sea surface temperature (SST) anomalies in the South China Sea (SCS) during developing autumn of various El Nino events. The warm SST anomalies are observed in the SCS for canonical El Nino and El Nino Modoki I, whereas the cold SST anomalies are found for El Nino Modoki II. The ocean heat budget analyses show that the latent heat flux change induced by various types of El Nino events is a major contributor to the SCS SST variations. An anomalous anticyclone resides near the Philippine Sea for canonical El Nino and El Nino 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. However, for El Nino Modoki II, the anomalous anticyclone shifts westward to the west of the SCS, and thus the northeasterly wind anomalies appear in the SCS. The northeasterly anomalies enhance the climatological northeasterly monsoon, increase the wind speed, and increase heat loss from the ocean, thus resulting in a cooling in the SCS. The anomalous anticyclone associated with El Nino events also increases shortwave radiation. The increases of the shortwave radiation can also contribute to the SCS warming for canonical El Nino and El Nino Modoki I in addition to the warm effect from the latent heat flux. Because the cooling effect from the latent heat flux is larger than that of the shortwave radiation for El Nino Modoki II, the SCS for El Nino Modoki II tends to be cool.