Application of P vector method to the diagnostic calculation of circulation in the South China Sea in summer

The P vector method is used to compute diagnostically the circulation of the South China Sea(SCS)in summer,based on the hydrographic data obtained during the SCScruise in June to July,1998.The results show that:The Kuroshio intrudes into the SCS,and then it makes a cyclonic meander to the northeast,and it finally has the trend of flowing out the SCS through the Bashi Channel.There is a cyclonic circulation in the northern part of the SCS,and its strength and scope decrease with the depth increases.There is a cold centre in this cyclonic circulation,and its position moves slightly the south with the depth increases.There are two obvious cyclonic and anticyclonic gyres in the central part of the SCS,and their scales are both about 250 km and they are quite stable above the 200 m level.The anticyclonic gyre lies to the east of Vietnam,and its centre is at 11°53'N,111°50'E.The centre of cyclonic gyre is at 13°17'N,112°55'E.There is an anticyclonic gyre west of Luzon Island.There is an anticyclonic gyre above 100 m level east of Balawan Island in the southern part of the SCS,but it becomes a cyclonic gyre at the levels below 200 m,and its current is quite weak.There is the intensify of curent in the western part of the SCS.