The subsequent data set contains global near-surface current estimates, derived using quasi-linear and steady flow momentum equations. The horizontal velocity (zonal: u- and meridional: v-components) is a vertical average over a surface layer thickness of 30 m and is directly estimated from sea surface height, near surface vector wind and sea surface temperature data as described in brief in the Users Guide.
The data used were collected from various satellites and in-situ instruments. These comprise
- gridded SSH anomalies (AVISO)
- an absolute SSH product based on 7 years of GRACE mission data, altimetry and hydrologic and drifter data
- Near surface wind velocity (SSM/I until 07/1999, QuikSCAT (and presumably ASCAT) from 08/1999 until present
- Reynolds SST at weekly temporal resolution
The model formulation used combines geostrophic, Ekman and Stommel shear dynamics, and a complementary term from the surface buoyancy gradient [Bonjean and Lagerloef, 2002]. More details about the method are also given on the OSCAR webpage.
For both grid resolutions u- and v-components are given. For the 1 degree product additionally filtered velocities are included; see the OSCAR webpage for more information. For the 1/3 degree product additionally so-called "Maximum mask velocities" are included; these are basically the geostrophic component at every grid point plus any concurrent Ekman and buoyancy components. Inclusion of this latter product is driven by the different coverage of the gridded input data sets.
Last update of this data set at ICDC: December 15, 2017.