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Ssalto/Duacs processing

There are three key features in Duacs: homogeneous products built on heterogeneous data flows from all missions, data centers, agencies and product types; shortest delay based on robust software, operational hardware and 24/7 operators; highest quality based on altimetry and oceanography expertise and on strict quality control.

 

Data used

  •   GFO IGDR and GDR files, provided by Noaa.
  •   Jason-1 and Envisat IGDR and GDR files, delivered by the Ssalto/CMA data server.
  •   Topex/Poseidon GDR data, provided by Po.Daac.

Various Dynamic Auxiliary Data (DAD) are needed to process these altimetric data (ECMWF, TEC grids from JPL, NRT Mog2D corrections…)

Overview of the Ssalto/Duacs system

  • Data acquisition and homogeneisation, where most recent corrections, models and references recommended for altimeter products are applied.
  • Input data quality control. 
  • Multi-mission Cross-calibration, based on two different algorithms: a global multi-mission crossover minimization for orbit error reduction (OER), and Optimal Interpolation (OI) for long wavelength error (LWE).
  • Along-track Sea Level Anomaly (SLA) and Absolute Dynamic Topography (ADT) product generation for each mission.
  • Merging process: the mapping procedure is based the OI software used for LWE reduction, then used to merge data from all missions in a single map of SLA or ADT.
  • Quality Control.

Ssalto/Duacs References

  • Dorandeu, J., and P.-Y. Le Traon, 1999: Effects of global mean atmospheric pressure variations on mean sea level changes from Topex/Poseidon, J. Atmos. Oceanic Technol., 16, 1279-1283.
  • Ducet, N., P.-Y. Le Traon, and G. Reverdin, 2000: Global high resolution mapping of ocean circulation from Topex/Poseidon and ERS-1 and -2, J. Geophys. Res., 105 (C8), 19477-19498.
  • Le Traon, P.Y., Faugère Y., Hernandez F., Dorandeu J., Mertz F. and M. Ablain, 2003. Can we merge GEOSAT Follow-On with TOPEX/POSEIDON and ERS-2 for an improved description of the ocean circulation? J. Atmos. Ocean. Techn., 20, 889-895
  • Le Traon, P.-Y. and F. Ogor, 1998: ERS-1/2 orbit improvement using TOPEX/POSEIDON: the 2 cm challenge. J. Geophys. Res., 103, 8045-8057.
  • Pascual A., Faugère F., Larnicol G., Le Traon P.Y, 2006, Improved description of the ocean mesoscale variability by combining four satellite altimeters, Geophys. Res. Let., Vol 33, L02611
  • Pujol I. and G. Larnicol, 2005, Mediterranean Sea eddy kinetic energy variability from 11 years of altimetric data, J. Mar. Syst. 58 (3-4), 121-142
  • Scharroo, R., and P. Visser, 1998: Precise orbit determination and gravity field improvement for the ERS satellites, J. Geophys. Res., 103 (C4), 8113-8127.