This data set is only available for a restricted user group, please contact us if you want to access these data.
RESTRICTED only accessable in CEN/MPI network or via CliSAP login What does that mean?
Data access via file system: /data/icdc/ocean/oscar_surface_current_velocity/
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
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: October 25, 2019.
Period and temporal resolution:
Coverage and spatial resolution:
The data set does not contain estimates of the uncertainty.
The authors of the data set note that the gridded data sets used to generate the OSCAR products (see description) create errors in the product due to, e.g. clouds, high wind velocity and rain in case of the near surface wind velocity and SST, residual orbit errors and long wavelength errors in case of the SSH products, and formal mapping and sampling errors.
The OSCAR product accuracy and representativity is limited by the usage of a simplified diagnostic model of the surface circulation. Effects on the near surface currents due to local acceleration and non-linearities are not taken into account. This limits the applicability of the OSCAR product to rather larger spatial scales (> 5° in longitude) and low frequency variations (> 20 days).
The authors of the data set note that the Johnson et al. (2007) paper is a bit outdated because in the current version (2009f for the 1/3 degree data set) an updated version of the AVISO SSH anomaly is used which reduced uncertainties.
For differences in the methodology used between the 1 degree and the 1/3 degree product we refer to the Users Guide.
We note that both the land mask and the sea ice mask change kind of irregularly in the two products and a not consistently used - which might prevent usage of the product too close to the coast and in certain basins.
1 degree data set:
1/3 degree data set:
When using the data please cite:
Bonjean F. and G.S.E. Lagerloef, 2002: Diagnostic model and analysis of the surface currents in the tropical Pacific ocean, J. Phys. Oceanogr., 32, 2938-2954.
and for the 1/3 degree data:
ESR. 2009. OSCAR third degree resolution ocean surface currents. Ver. 1. PO.DAAC, CA, USA. Dataset accessed [2019-10-15] at http://dx.doi.org/10.5067/OSCAR-03D01.
while for the 1 degree data use:
ESR. 2007. OSCAR 1 degree ocean surface currents. Ver. 1. PO.DAAC, CA, USA. Dataset accessed [2019-10-15] at http://dx.doi.org/10.5067/OSCAR-10D01.