Antisymmetric responses of sea surface temperature trend in the South China Sea during maturity and decaying periods of CP El Niño events

Abstract Compared with the eastern El Niño events (EP), the central El Niño events (CP) impacts the sea surface temperature (SST) anomalies in the South China Sea (SCS) in various periods variously, which further affect the local hydrodynamic processes and ecological environment. We investigate that the SCS SST anomalies of the CP El Niño events experiences a transition from rapid warming and cooling during maturity and decaying periods, respectively, which is opposite and stronger than the EP El Niño events. Spatially, the distribution of SST anomalies trend in the SCS is antisymmetric in two periods. Heat budget analysis shows that during the maturity period, the warming trend of SST anomalies is determined by the net heat flux and horizontal heat advection. The net heat flux exerts a greater influence in the north, with latent heat flux being the principal factor which is influenced mainly by weakened wind-speed, whereas horizontal heat advection is more influential in the south. During decaying period, the basin-scale cooling is mainly caused by net heat flux, with the reduced short-wave is the main contributor of negative net heat flux, attributed to increased cloudiness resulting from weakened wind-speed, whereas horizontal heat advection plays an inhibitory role. Latent heat flux is the major factor in causing regional antisymmetric responses. During maturity period, in response to the anticyclone near the Philippines sea, the anomalous southwesterly and northeasterly winds were observed in the northern and southern parts of the SCS, respectively. However, this anticyclone is intensified and drifted northeastwardly in decaying period, resulting in the northeasterly winds over SCS. The shift of wind field on horizontal heat advection and net heat flux is the main mechanism modulating the antisymmetric SST trend in two periods. This study enhances the understanding of SST evolution and sea-air interactions of CP El Niño events.