"Computation of a new mean dynamic topography for the Mediterranean Sea from model outputs, altimeter measurements and oceanographic in situ data" by Rio et al., has been published in Ocean Science Journal

SOCIB, CLS, OGS and IMEDEA (CSIC-UIB) released a new Mean Dynamic Topography for the Mediterranean Sea (SMDT-MED-2014). The new Mean Dynamic Topography benefits from the use of the new multi-platform observing systems approach to ocean observation, extended datasets and refined processing. The updated dataset spans the 1993-2012 period (versus 1993-1999 for the previous version) and consists of: drifting buoy velocities provided by OGS, altimetry data provided by CLS, hydrological profiles provided by EN3, IMEDEA (CSIC-UIB), SOCIB and IEO and numerical model output provided by INGV.

The methodology is similar to the previous MDT (Rio et al. 2007), except that in Rio et al (2007) no hydrological profiles were considered. This has required the development of dedicated processing. A number of sensitivity studies have also been carried out to obtain the most accurate MDT as possible, showing moderate impact of the choice of correlation scales, but almost negligible sensitivity to the choice of the first guess (model solution).

A systematic external validation using independent data has been made in order to evaluate the performance of the new MDT. Compared to previous version, SMDT-MED-2014 features smaller scale structures, which results in an altimeter velocity variance closer to the observed velocity variance and, at the same time, gives better Taylor skills. This result is of significant scientific interest since semi- enclosed seas such as the Mediterranean, are challenging regions for the use of altimetry data, since the spatial scales of the oceanic structures are smaller than in the open ocean. More specifically, this new MDT allows an improved description of the main currents and semi-permanent structures of the Mediterranean Sea, with an improved description of major currents as the Liguro-Provençal current, or known structures as the Bonifacio gyre, compared to the previous SMDT07 solution. In addition, spurious currents present in the SMDT07 solution have now disappeared (along the Spanish Catalan coast for instance).

This new MDT is therefore an important tool to characterise the state and variability of the Mediterranean Sea from observations. Such a tool that will also be important in the assimilation of SLA into operational forecasting systems in the Mediterranean.

For specific information on the algorithm see:

  • M.-H. Rio, A. Pascual, P.-M. Poulain, M. Menna, B. Barceló, and J. Tintoré. Computation of a new mean dynamic topography for the Mediterranean Sea from model outputs, altimeter measurements and oceanographic in situ data. Ocean Sci. , 10, 731-744, 2014. http://www.ocean-sci.net/10/731/2014/os-10-731-2014.html   doi:10.5194/os-10-731-2014.