Ocean forcing of tidal winds: evidence from harmonic analysis of altimeter-derived wind speed
Event: 2023 Ocean Surface Topography Science Team Meeting
Session: Tides, internal tides and high-frequency processes (ROUND TABLE)
Presentation type: Type Poster
Contribution: PDF file
Because the wind stress at the ocean surface depends on the difference in speed between the ocean surface current and the surface wind, the direction of transfer of momentum and energy between the ocean and atmosphere can vary as a function of spatial or temporal scale. Analysis of coupled models of the ocean and atmosphere have suggested that in regions of strong tidal currents, as found on some continental shelves, the ocean currents may accelerate the atmosphere and generate significant surface winds with speed around 1/3 that of the ocean currents (Renault and Marchesiello, 2022). This suggestion is examined here through tidal harmonic analysis of altimeter-derived wind speed from the Jason missions and comparison with predicted barotropic tidal currents on the continental shelves. A handful of sites are identified where M2 semidiurnal variations in wind speed are collocated with strong tidal currents, with the continental shelf off the Amazon River being noteworthy. Separate harmonic analysis of backscatter (sigma0) and significant wave height (Hs) indicates that the tidal wind speed modulations are primarily a result of sigma0 variability; although, some intriguing tidal variability of Hs is found. The correspondence between predicted tidal currents and measured wind speed is not so tight as to justify an evaluation of the scale factor between them, but the relative locations of tidal current and wind speed maxima may be informative about tide model errors.