Discussions On The Movement Of Mesoscale Eddies In The South China Sea

There are many mesoscale eddies in the South China Sea. A composite time series (1993-2000) of sea surface height anomaly from several satellites is used to discuss the life historic statistics, especial the movement of mesoscale eddies. Altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period. They are grouped into four geographical zones according to known eddy generation mechanisms, and their statistics are discussed accordingly.The variation of the sea surface height (SSHA) dipole structure off center Vietnam in summer is analyzed using a series of satellite data. Principal Component Analysis is applied to discuss the principal modes of SSHA and wind stress curl. Results show that the two fields have a good lag correlation. Furthermore, A reduce gravity numerical model is applied to discuss the mechanism of the dipole structure generation and its evolution. Wind structure and are preconditions to form the dipole structure, and the vorticity transport from the nonlinear term results in the formation of dipole structure. This mechanism is similar to the formation of the recirculation of wind-driven general circulation in northern Pacific or Atlantic.By comparing model experiments forced with either QuikSCAT or NCEP winds, we examine the impact of small-scale wind features on the mesoscale simulation of the South China Sea. It indicates the wind stress curl associated with land topography may be an important mechanism to form those eddies that lie near southwest of Taiwan island, northwest of Luzon island and southwest of Luzon island in winter. The effects of QuikSCAT wind forcing with different spatial and temporal resolutions are also evaluated.