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ADT-H - Absolute Dynamic Topography (along-track)

Types of dataset: Ssalto/Duacs along-track multimission altimeter products
Contents: along-track sea surface heights above geoid; dynamic topography is the sum of sea level anomaly (SLA) and mean dynamic topography (MDT), both being referenced over a twenty-year period in the Duacs 2014  version (V15.0). On this basis, the ADT is unchanged  since the ADT products have been caluclated with consistent SLA and MDT field
Use: study of the general circulation (ocean gyres ...)
Condition of access : All Ssalto/Duacs product users need an account on FTP, see Access to Ssalto/Duacs data
Data access service: Along-track products are only delivered through the authenticated FTP server.
Description: mono altimeter satellite product homogeneous with other satellites, available in near-real time and in delayed time.
Geographic coverage: global. A specific regional product with an improved quality is available in local areas (more information).

Formats: NetCDF-CF



Description: this delayed time product is available in two series:

  • "filtered" serie (vfec) : validated + filtered + subsampled + correction for LW (long wavelengh) errrors product. Residual noise and small scale signals are removed by filtering the data using a Lanczos filter. As data are filtered from small scales, a sub-sampling is finally applied.  As a consequence, for a given date, the distance between each measurement is bigger in a "vfec" file than in the "vxxc" file. Note that the filtering and sub-sampling is adapted to each region and product as a function of the characteristics of the area and of the assimilation needs (see details in the handbook, section "Filtering and Sub-sampling" for Delayed-Time products). Users that need to use a measurement with noise error reduced should rather user this filtered product.
  • "unfiltered" serie (vxxc): validated + non filtered + non subsampled + correction for LW errrors. This product keeps the full 1Hz resolution. This means that for a given date, the number of measurements is bigger in a "vxxc" file than in the vfec file. Moreover, the uncorrelated measurement noise is not reduced (because of non filtering). Users that need the full 1 Hz measurements should use this unfiltered product keeping in mind that it is affected by the full 1Hz measurement noise error.

Copyright : 1993-ongoing CLS - Cnes

Access service Frequency Data period File weight
Saral FTP: unfiltered
FTP: filtered
3-4 months From mars-13 to janv-16 700 Ko per file (zipped)
Cryosat-2 From Apr-12 to janv-16
Jason-2 From oct-08 to janv-16
Jason-1 (j1, j1g, j1n) From Apr-02 to juin-13
Envisat (en, enn) From oct-02 to Apr-12
ERS-1 From oct-92 to May-95
ERS-2 From May-95 to Apr-03
T/P(tp, tpn) From sept-92 to oct-05


Description : Only "filtered" version ("vfec", see description above) is delivered. FTP delivers daily the most recent data: the most recent file is updated several times per day in order to include the most recent available OGDR data.
Data period : within a few months at most, from the latest update of the DT products to today.
Copyright : 2004-ongoing CLS-Cnes.

Access service
Frequency Delivery delay Data period File weight
Jason-3 authenticated FTP: filtered Daily 3 hours to 3 days From sept-16 today 2.5 MB per file (zipped)
Saral Daily 3 hours to 3 days From janv-16 to today 350 Ko per file (zipped)
Cryosat-2 Daily 3 hours to 3 days (best effort) From janv-16 to today 300 Ko per file (zipped)
Jason-2 Daily 3 hours to 3 days From janv-16 to sept-16 2.5 MB per file (zipped)
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