How are geostrophic velocities computed at the Equator?
In the geostrophic velocity data distributed by Aviso today, current velocities at the equator are computed using equatorial geostrophy [Picaut et al., 1989]. At the Equator, (lat = 0) we use second derivative. This method is quite usual. In a 5° band around the Equator, a connection is computed to ensure continuity with classical geostrophy. This continuity is not completly satisfying just now, so a study was conducted to test the connection proposed by Lagerloef et al. [1999]. The improvement thus obtained is significant, and was validated using TAO measurements.
