| Analysis and calculation were given based on Jason-1 satellite altimetry, CTD and ADCP data, which were sampled from Aug. 15 to Sept. 6 in the 2007 Summer Cruise within the area 11°N～15°N, 110°E～114°E.Satellite altimetry data were used to determine the locations, scales and life-spans of the mesoscale eddy A and B, respectively. Cold eddy A which lasted from Aug. 15 to Sept. 6, merged at 13.75°N, 112.25°E with a diameter around 120km. On Aug. 26, cold eddy B show up at 11.75°N, 110.5°E with a diameter about 150km. Further description to the characteristics of those two mesoscale eddies were carried out based on the analysis of spatial structures of temperature, salinity, density and absolute velocity fields.3-D density and absolute velocity field were used to obtain the absolute dynamic height field via the numerical solution of 2-D Omega equation. The geostrophic velocity field was calculated due to the geostrophic balance. Geostrophic velocity field is generally cyclonic pattern. At the outskirt of gyre, geostrophic velocity was up to approximately 1m/s. Given the 3-D geostrophic velocity field, velocity of vertical circulation could be diagnosed using 3-D Omega equation. Usually vertical velocity in the inner ocean owned the magnitude of O(10-2 ) m d-1. But due to the presence of mesoscale eddies, vertical velocity here was up to 6m d-1 and 15m d-1 at cold eddy A and B, respectively. The accuracy of the vertical velocity could be impact by following aspects, such as, the assumption of quasi-geostrophic balance, the interpolation of raw density data, the choice of boundary conditions and the assumption that each survey was a synoptic one with high resolution.
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