Towards a global Stokes drift product from SWIM/CFOSAT

The Stokes drift is the main contribution from ocean surface waves to particles drift in the ocean's upper layer. At the moment, estimates of the Stokes drift at the global scale rely on numerical models, due to the unavailability of such measurements from space. CFOSAT is a new mission concept, carrying SWIM, a rotating scatterometer, operating both at nadir and off-nadir. It aims at measuring the ocean surface waves slopes spectrum, from which the Stokes drift can be estimated. Potential for Stokes drift estimation from SWIM is illustrated using statistical diagnostics on SWIM ocean waves spectra. Although the Stokes drift is carried in majority by waves which are not resolved by SWIM, it is shown that an algorithm based on the extrapolation of SWIM waves spectra could be thought of. Such potential combined with the characteristics of SWIM make the effort to design and qualify a Stokes drift product interesting. Such a product would be of particular interest in areas such as the Southern Ocean, where Stokes drift is significant and poorly known, and where the observational conditions are favorable to SWIM (resolved wind sea, favorable wave direction)