EDDY STATISTICS IN THE SOUTH-ATLANTIC AS DERIVED FROM DRIFTERS DROGUED AT 100 M

More than 130 satellite-tracked buoys drogued at 100 m depth have been deployed by us in the South Atlantic during the years 1990-1993 in an ongoing program. After eliminating those portions of the trajectories for which the drogue was off, Lagrangian eddy statistics are computed and compared to the results of a similar data set in the North Atlantic and to previous results for the South Atlantic. Regarding the relations based on Taylor's theory, no significant differences can be seen between the North and South Atlantic. The Lagrangian integral time scale is inversely proportional to the r.m.s.-velocity which implies that eddy diffusivity is directly proportional to the r.m.s.-velocity and not to the variance. Previous studies on that matter are most likely influenced by buoys which lost their drogue. Eddy length scale is constant with values of 37 km in zonal and 28 km in meridional direction, averaged over the entire Atlantic. Eddy diffusivity varies between 2.10(7) and 8.10(7) cm(2)/s, being smallest in the subtropics and highest in the Circumpolar Current. The proportionality to eddy velocity and a constant length scale opens the possibility to compute global distributions of eddy diffusivity from altimeter data.