An airborne expendable bathythermograph survey of the South China Sea, May 1995

An extensive airborne expendable bathythermograph survey of the South China Sea (SCS) conducted in May 1995 and historical data are used to analyze and infer the upper layer (300 m) synoptic structure and general circulation. The primary thermal feature observed was a central SCS warm pool surrounded by several cool pools. The size of the warm pool decreased with depth from approximately 200,000 km 2 at 50 m depth to about 70,000 km 2 at 300 m depth. The maximum temperature of the warm pool was 30°C, appearing near the surface. At the depth of 50 m, the temperature of the central SCS warm pool was 29°C, and the temperature of the five surrounding cool pools ranged from 26°C to 22°C. A three‐dimensional estimate of the absolute velocity field was obtained from the observed temperature field and a climatological salinity field using the β spiral method. Striking circulation features were the existence of dual anticyclonic eddies in the central SCS warm pool and the existence of cyclonic eddies associated with the cool pools. In the upper layer the tangential velocity of the dual central SCS anticyclonic warm‐core eddies is around 30–40 cm/s and that of the five cyclonic cool‐core eddies varies from 10 cm/s to 40 cm/s. The tangential velocity of all the eddies decreased with depth. At 300 m depth, it became less than 5 cm/s for all the eddies.