Global surface currents: a high-resolution product for investigating ocean dynamics |
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| Authors: | Joel Sudre Rosemary A Morrow |
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| Institution: | (1) CTOH/LEGOS, 18 av. E. Belin, 31401 Cedex 9 Toulouse, France |
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| Abstract: | A global 1/4° resolution product of surface currents has been developed by the Centre de Topographie des Océans et de l’Hydrosphère.
The surface current is calculated from a combination of Ekman currents derived from wind estimates from QuikSCAT satellite,
geostrophic current anomalies derived from altimetry, and a mean geostrophic current derived from climatology. In the equatorial
band, the currents are adjusted following the methodology proposed by Lagerloef et al. (J Geophys Res, 104(C10):22313–22326,
1999). These satellite-derived currents have been compared to different types of in situ current observations. A global validation
is performed using Lagrangian surface drifting buoys and acoustic Doppler current profiler current observations along ship
tracks. The comparison shows a very good agreement in the subtropical and mid-latitude bands. The correlation between the
satellite-derived currents and the drifter currents in zonal mean bands is around 0.7 for most of the world oceans, both for
the zonal and the meridional components. This correlation rises up to 0.8 in the regions of strong boundary currents. In the
equatorial band, the correlation with the surface drifting buoys is reduced. A direct comparison with the TOGA/TAO moored
current meter data at the equator shows that the low frequency currents are captured by the satellite current product, but
there is a substantial high-frequency signal (<20 days), which is not reproduced. This is especially the case for the meridional
component and is mainly related to the tropical instability waves. We also show that using daily QuikSCAT wind forcing improves
the satellite current product, particularly in the high-latitude westerly wind belt and in the tropical Indian Ocean. |
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| Keywords: | Ocean surface currents Satellite altimetry Scatterometry winds In situ currents |
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