The Rio05 Combined Mean Dynamic Topography (CMDT)

The issue of estimating a global Mean Dynamic Topography (MDT) is to reference the altimeter Sea Level Anomalies (SLA), computed relative to a 7 year (1993-1999) mean profile, in order to obtain absolute measurements of the ocean dynamic topography.
Required MDT has to be consistent with altimeter physical content and shall therefore correspond to the mean over 1993-1999 of the geostrophic, barotropic and baroclinic ocean circulation.

This work combines several steps:

• We first use a direct method to estimate at large scale a MDT using the CLS01 MSS and the EIGEN-GRACE 03S geoid. This MDT is then merged with the Levitus climatology MDT to provide our first guess.
   
• Then we use a synthetic method to improve the mean circulation infered from this first guess, using hydrographic and Lagrangian data together with altimeter Sea Level Anomalies over the 1993-2002 period. The global MDT is then compared to other surfaces.
   
• Finally, we used independant drifter data to compare Rio05 with ECCO, Levitus, and Le Grand derived MDT.

See also Rio05 references & publications.