The OSCAR (ocean surface current analysis real-time), which is a product derived from various satellite observations, has been evaluated in the tropical Indian Ocean (TIO) in two different ways. First, the OSCAR-derived monthly climatology has been compared with available drifter-derived climatology in the TIO. From the comparison of the two climatologies, one can infer that OSCAR product is able to capture the variabilities of the well-known surface current systems in the TIO reasonably well. Fourier analysis of the major current systems, as reproduced by OSCAR, shows that the dominant annual and semiannual periodicities, known to exist in these systems, have been faithfully picked up by OSCAR. Next, the evaluation has been carried out by comparing the OSCAR currents with currents measured by moored buoys. The zonal component of OSCAR-current is in good agreement with corresponding component of buoy-observed current with a correlation exceeding 0.7, while the match between the meridional components is poorer. The locations of the peaks of the mean and eddy kinetic energies are matching in both the climatologies, although the peak in the drifter climatology is stronger than the same in the OSCAR product. Finally, an important feature of Indian Ocean circulation, namely the reverse Wyrtki jet, occurring during anomalous dipole years, has been well-reproduced by OSCAR currents.

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This letter deals with the development of geophysical model functions (GMFs) specific to Oceansat-2 Scatterometer (OSCAT) for the operational retrieval of global ocean surface vector winds from OSCAT. It makes use of OSCAT-measured radar backscatter and the surface analysis winds at 10-m neutral-stability height from the European Centre for MediumRange Weather Forecasts (ECMWF) model for the period from November 2009 to April 2010. The OSCAT-specific GMF has been used for retrieving the vector solutions from backscatter data as well as for the directional ambiguity removal. The procedures and the conditions incorporated for the same are presented in this letter.Index Terms-Geophysical model function, Oceansat-2, ocean surface wind vector, scatterometer.

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