The kinematics of mesoscale eddies from TOPEX/Poseidon altimetry over the Subtropical Counter Current

Abstract

TOPEX/POSEIDON altimetry data were used to track mesoscale eddies over the Subtropical Counter Current (STCC). The radii, centers, vorticities, shearing deformation rates, stretching deformation rates, divergences and center velocities of all identified eddies over STCC were determined using a model that assumes constant velocity gradients. A case study was made for a cyclonic eddy and an anticyclonic eddy, with time series of eddy kinematic parameters computed. Both eddies survive for about 220 days and propagate westwards along over 22degreesN-24degreesN to reach the Kuroshio Current east coast of Taiwan. Sea surface temperature data confirm the existence of these two eddies. The radii of both eddies vary and their shapes are mostly elliptical during propagation. The anticyclonic eddy propagated almost westwards with oscillating north-south components, and the mean speed is 8.3 km/day. The cyclonic eddy moved southwestwards before reaching 130degreesE and then moved northwestwards, with a mean speed of 7.6 km/day. The propagations of these two eddies are basically consistent with the standard theory of eddy propagation but with larger speeds and varying propagating directions.