Abstract

Validation and Error Analysis of OSCAR Sea-surface Currents

Fabrice Bonjean
Earth and Space Research, Seattle, WA 98102-3620.

Gary S.E. Lagerloef
Earth and Space Research, Seattle, WA 98102-3620.

John T. Gunn
Earth and Space Research, Seattle, WA 98102-3620.

Gary T. Mitchum
College of Marine Science, University of South Florida, St. Petersburg, FL

Comparison of OSCAR satellite-derived sea surface currents with /in
situ/ data from moored current meters, drifters, and shipboard current
profilers indicate that OSCAR presently provides accurate time-means of
zonal and meridional currents, and in the near-equatorial region
reasonably accurate time variability (correlation = 0.5 to 0.8) of zonal
currents at periods as short as 40 days and meridional wavelengths as
short as 8°. At latitudes higher than 10° the zonal current correlation
remains respectable but OSCAR amplitudes diminish unrealistically.
Variability of meridional currents is poorly reproduced, with amplitudes
badly underestimated and correlations diminished relative to those for
zonal velocity, especially on the equator. OSCAR's RMS differences from
drifter velocities are very similar to those experienced by the ECCO
data-assimilating models, but OSCAR generally provides a larger
ocean-correlated signal which enhances its ratio of estimated signal
over noise. Several opportunities exist for modest improvements in OSCAR
fidelity even with presently available data sets.