Marine Science Faculty Publications

Document Type


Publication Date


Digital Object Identifier (DOI)


Tropical surface currents are estimated from satellite-derived surface topography and wind stress using a physically based statistical model calibrated by 15 m drogue drifters. The model, assumes a surface layer dominated by steady geostrophic and Ekman dynamics. Geostrophy varies smoothly from a beta plane formulation at the equator to an f plane formulation in midlatitude, with the transition occurring at similar to 2 degrees-3 degrees latitude. The transition is treated with a Gaussian weight function having a meridional decay scale that is found to be approximately the Rossby radius (similar to 2.2 degrees latitude). The two-parameter Ekman model represents drifter motion relative to wind stress, with downwind flow along the equator and turning with latitude. Velocities computed from satellite data are evaluated statistically against drifter velocities and equatorial current moorings. Examples of the geostrophic and Ekman flow fields in the western Pacific during a westerly wind burst in late December 1992 depict a strong eastward flow and equatorial convergence. A comparison between December 1996 and June 1997 illustrates the basin-wide reversal of equatorial surface flow during the onset of the 1997 El Nino.

Was this content written or created while at USF?


Citation / Publisher Attribution

Journal of Geophysical Research, v. 104, issue C10, p. 23313-23326

Copyright 1999 by the American Geophysical Union.