The South China Sea (SCS) is the largest marginal sea in the western Pacific, which directly connects with the West Pacific through the Luzon Strait (Fig. 1) to the northeast. Its central deep basin with maximum depth 4 5000 m is boarded by two broad shelves of o 200 m depths in the northwest and in the southwest SCS. As located in the East Asian Monsoon (EAM) regime, the SCS is influenced by a seasonally alternating wind stress field, which consequently causes seasonal change of surface circulation (Hu et al., 2000).