Surface Drifters			Abstract Introduction Model Descriptions Surface Drifters Numerical Trajectories Eulerian Statistics Mean Velocity Vectors MKE Ellipses EKE James test Lagrangian Statistics Diffusivities Time Scales Length Scales Summary Appendix A Appendix B Acronyms References Acknowledgements Forum
Observed velocities used in this study were obtained from the global surface drifter data archives of the NOAA Atlantic Oceanographic and Meteorological Laboratory. The instrument used is the World Ocean Circulation Experiment/Tropical Ocean-Global Atmosphere experiment (WOCE/TOGA) Lagrangian drifter (Sybrandy and Niiler, 1991) with a drogue at 15-m nominal depth. Drifter velocities were extracted for the years 1993-1997 for the North Atlantic domain, defined here as 20°N-70°N and 80°W-20°E. The velocities were corrected for drogue slippage resulting from wind effects using a formula based on regression analyses of a complete worldwide database of drifters and global wind products (Pazan and Niiler, 2001). The data were then sub-sampled at daily intervals to match the time of the model snapshots. Concentrated releases were made off Cape Cod and the coasts of Norway and Iceland, between the Azores and Canary Islands, east of the mid-Atlantic ridge between 44°N and 49°N, and in the Labrador Sea. The composite trajectory plot reflects the dispersion from the deployment sites, with high drifter data densities corresponding to the areas of intense deployment.
Enlarge	The drifter trajectories clearly show a coherent Gulf Stream and northern boundary currents, while the southeast basin is characterized by circuitous, rambling patterns. The coverage of the open ocean waters is extensive and few areas without drifter data are apparent. Particular regions lacking coverage are the western boundary of the Labrador Sea, the wide continental shelves off Canada, the marginal seas off western Europe, and over the African shelf.