The surface currents data are from the U.S. Coast Guard's Mariano Global Surface Velocity Analysis (MGSVA) Project directed by the Rosenstiel School of Marine and Atmospheric Science at the University of Miami, Florida. The temporal resolution of the surface current data is monthly while the horizontal resolution is one degree longitude and latitude.
The data was acquired by tracking the movement of several hundred drifting buoys using a satellite. Most of the drifters were equipped with devices to compensate for wind and wave action. These devices were large holey-sock drogues, centered at a depth of 15 m. Ocean currents were estimated by taking the temporal difference of nearby drifter positions. The drifters transmit sensor data to satellites which determine the buoy’s position and relay data to ground stations for processing and distribution. More information about the drifting buoys and the entire Global Ocean Current Velocity Project is described here.
The downloadable data is available here in ASCII tabular text form with fields representing the geographic coordinates, current velocity, and the x (east-west) and y (north-south) vector components of current directions. Azimuthal directions ranging from 0° to 360° have been calculated locally and a raster of these ocean current directions has been created.