Studies on the sea-surface current-circulation pattern in the South China Sea derived from satellite altimetry

Radar altimeters flown in space are very useful tools for providing information about the ocean globally and continuously, including the study of surface currents. This research is concerned with the geostrophic currents in the South China Sea. Maps of geostrophic current-circulation patterns are produced for four periods, which are the northeast monsoon, the southwest monsoon and the inter-monsoon periods for April and October in 2004 and in 2005. The main data utilised are the sea-level anomaly from Jason-1 satellite altimetry data. To compute the geostrophic current velocity, the geostrophic equations were used. In order to validate the derived surface current, the correlation coefficient with field measurement data was determined. The field data are measured using Lagrangian buoys under the Data Buoy Cooperation Panel programme (DBCP) and also from the Japanese Oceanography Data Centre (JODC). In this study, it was found that the correlation of geostrophic current speed and direction is reasonable with coefficient of 0.9 and 0.7, respectively. As far as the geostrophic current-circulation pattern is concerned, the current in the South China Sea was pushed southward during the northeast monsoon and reversed during the southwest monsoon period. In addition, during the northeast and southwest monsoon, the water moved in anticlockwise and clockwise directions, respectively. This leads to the conclusion that the geostrophic circulation pattern can be monitored from satellite altimetry data