SEASENAL AND INTERANNUAL VARIATIONS OF THE THERMOCLINE DEPTH IN THE SOUTH CHINA SEA

Based on SODA(Simple Ocean Data Assimilation)and NCEP data,the seasonal and interannual variation of the thermocline depth in the South China Sea was analyzed and the main reason for the thermocline depth anomalies during the El Nio event was discussed in this article.According to the analysis,the seasonal and interannual variation rule of the thermocline depth is obvious in the South China Sea.Thermocline depth is deeper in winter than that in summer,and it is in a transtion state in spring and autumn.Affected by Ekman transport caused by the monsoon,the thermocline is shallower in the southeastern South China Sea than that in the northwestern South China Sea in winter while the thermocline is deeper in the southeastern South China Sea than that in the northwestern South China Sea in summer.The thermocline depth is deeper in fall than in spring.During the El Nio event,the thermocline depth in most of the South China Sea shows negative anomalies from October[0]to March [+1],which is consistent with the time range of the high value of Nino3 index.The thermocline depth in most of the South China Sea shows positive anomalies from April[+1]to June[+1].The main factors to affect the thermocline depth in the South China Sea are net heat flux,stir of wind stress,wind stress curl and Ekman transport.Stir of wind stress and the net heat flux is dominant in the South China Sea during the El Nio event.