These data sets will cover:

• 1986/1989, with data from GEOSAT
• 1992-2004, with data from T/P and ERS-1/2 then Jason-1 and ENVISAT.

All these altimeter data sets will be fully reprocessed to provide a homogeneous, inter-calibrated and highly accurate long time series of SLA and MSLA altimeter data. In particular, improved altimetric corrections and processing algorithms will be used: better ocean tide model to correct altimeter data, improved methods for orbit error reduction and mapping.

In addition, near real time altimeter data sets will be produced by the SSALTO/DUACS system. This system delivers near-real-time SLA and MSLA combining data from different altimetric missions (TOPEX/POSEIDON, ERS-2, Jason-1, ENVISAT, GEOSAT follow on).

Find more information on altimetry on the AVISO web site.

A mean dynamic topography is essential to reference SLA altimeter data and get absolute dynamic topography. A precise mean dynamic topography will have a major impact on scientific and operational applications of satellite altimetry (e.g. Woodworth et al., 1998; Le Provost et al.,1999) :

• better interpretation of altimeter signals
• comparison/combination with in-situ data
• general circulation and heat transport
• data assimilation and ocean forecasting

In this project, a global mean dynamic topography will be obtained by combining the CHAMP geoid data with available in situ data and altimeter data using a synthetic geoid methodology. It will then be used by ENACT partners to assimilate altimeter data.

Find more with the poster: "Estimation of a global mean dynamic topography using altimetry, gravimetry and in situ data" - M-H Rio, F.Hernandez, D. Tamagnan, F. Davidson, S. Guinehut.
part 1 (PPT - 1892 Ko) and part 2 (PPT - 1514 Ko)

Systematic comparison of in-situ (temperature and salinity profiles, tide gauges) and altimetry will be carried out as part of ENACT to gain information on:

• the vertical structure of sea level variability (barotropic/baroclinic)
• sampling errors, salinity effects, inconsistencies between means

This information is crucial to effectively merge in situ and altimeter data through assimilation.

Find more with the poster "Comparison of altimetry and hydrography over the global ocean" - S. Guinehut, G. Larnicol, PY Le Traon (PDF - 1354 Ko)