Numerical study on the interannual oscillation of sea surface temperature in the South China Sea

Abstract

A two and a half layer oceanic model of wind-driven, thermodynamical general circulation is applied to study the interannual oscillation of sea surface temperature (SST) in the South China Sea (SCS). The model consists of two active layers: the upper mixed layer (UML) and the seasonal thermocline, with the motionless abyss beneath them. The governing equations which include momentum, continuity and sea temperature for each active layer, can describe the physics of Boussinseq approximation, reduced gravity and equatorial β-plane. The formulas for the heat flux at the surface and at the interface between two active layers are designed on the Haney scheme. The entrainment and detrainment at the bottom of the UML induces vertical transport of mass, momentum and heat, and couples of dynamic and thermodynamic effects. Using leap-frog integrating scheme and the Arakawa—C grid the model is forced by a time-dependent wind anomaly stress pattern obtained from category analysis of COADS. The numerical results indicate that there is a kind of oscillation with about 30 months period. The paper supports the opinion that the SST interannual oscillation is the oceanic response to the forcing by monsoon wind anomalies in the SCS.