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 gener
al circulation. The primary thermal feature observed was a central SCS
warm pool surrounded by several cool pools. The size of the warm pool
decrease 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 war
m pool was 30 degrees C, appearing near the surface. At the depth of 5
0 m, the temperature of the central SCS warm pool was 29 degrees C, an
d the temperature of the five surrounding cool pools ranged from 26 de
grees C to 22 degrees C. A three-dimensional estimate of the absolute
velocity field was obtained from the observed temperature field and a
climatological salinity field using the beta spiral method. Striking c
irculation features were the existence of dual anticyclonic eddies in
the central SCS warm pool and the existence of cyclonic eddies associa
ted 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 d
epth. At 300 m depth, it became less than 5 cm/s for all the eddies.