Improvements to a Real-Time, Satellite-Derived Surface Current Product (OSCAR) and Evaluation in the Intra-American Sea

A method of creating real-time height fields using available gridded altimetry data combined with extrapolated values computed using linear predictive coding for use in the Ocean Surface Currents Analysis, Real-time (OSCAR) is developed and tested. This method is implemented by Earth and Space Research (ESR) to produce operational height fields that are in turn used to calculate the geostrophic component velocity of OSCAR. The gridded altimetry product used in OSCAR is evaluated against sea level measured by tide gauges while the operational total near-surface velocity from OSCAR (geostrophic plus Ekman component velocity) is evaluated using ocean velocities from moored and shipboard acoustic Doppler current profiler (ADCP) measurements. The evaluation is focused in the Intra-American Sea (IAS), having complex currents due its topography and bathymetry, and proves to be a challenging place for OSCAR to accurately reproduce ocean velocity. Issues are related to the upper limit in frequency that altimetry can capture, accuracy of altimetry near to land, the scale of the spatial smoothing across relatively narrow currents and geographical differences in the effective smoothing of the gridded altimetry used for OSCAR. These problems highlight the need for more and better ocean observing and modeling systems to provide data that can supplement the use of gridded satellite-derived products, especially in the IAS