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DUACS 2018 Two-sat gridded merged products now disseminated by C3S

The Copernicus Climate Change Service ( is now in charge of the processing and distribution of the DUACS "two-sat-merged" altimeter sea level  gridded products as they are produced on an operational basis for climate oriented applications. 

The variables available in the products are the Sea Level Anomaly (SLA), the Absolute Dynamic Topography (ADT) and the associated geostrophic velocities in the Global Ocean, Mediterranean and Black Seas in Delayed-Time. Compared to previous products disseminated by Aviso+, the time series has been fully reprocessed (DUACS DT-2018 standards). Detailed information are available in the product user guide

You can register here.

Please contact the C3S service desk if needed:

Duacs 2018 FSLE Delayed-Time reprocessing

In July 2018, a new version of the SSALTO/Duacs delayed time Finite Size Lyapunov Exponents (FSLEs) products distributed by Aviso, so-called FSLE DUACS 2018, has been released with several significant upgrades. A complete reprocessing of the whole FSLEs delayed time series has been performed.

Upgrades are the following :

-MADT_UV input data are derived from DUACS-DT 2018 instead of DUACS-DT 2014

-Data are now daily data 

-Initial separation is 0.02 degree instead of 0.04 degree

-Data availability has been extended to January 2018 18th

Data format remains unchanged and is NetCDF-4 Classic with CF standards.

Duacs 2018 Climatology Delayed-Time reprocessing

July 2018: Information about DUACS 2018 Climatology products changes and updates

In June 2018, a new version of the SSALTO/Duacs Climatology products distributed by Aviso, so-called Climatology DUACS 2018, has been released with several significant upgrades. A complete reprocessing of the whole L4 altimeter delayed time series has been performed. 

The L4 processing parameters impact the L4 Climatology products:

  • Higher Sea Level variance over high variability areas (Western boundary currents and circumpolar current for the Global product; Algerian current, Central and Nord Ionian, Ierapetra area for the Mediterranean Sea product)
  • Increase of the EKE over high variability areas (Western boundary currents and circumpolar current) and decrease over the equatorial band
  • Global reduction of the formal mapping error over the Global ocean; Global augmentation of the formal mapping error for the Mediterranean Sea product.
  • Modification of the contribution of the different missions in the L4 products

The positive impact of this new processing on the quality was demonstrated as part of the full reprocessing exercise. Indeed, the assessment of the whole-time series shows a significant improvement of the quality, with notably a better consistency with independent measurements. 

Information for Global data

Information for Blacksea data

Information for Mediterranean sea data

May 2017: End of Transition AVISO+ to CMEMS and new CMEMS version since April 19th

The European Copernicus Marine Environment Monitoring Service (CMEMS) is now in charge of the processing and distribution of some altimetry products formely distributed by AVISO+. Indeed AVISO+ now focuses on the distribution of innovative products whereas CMEMS is dedicated to the operational products and services. Since CMEMS Version3 (April 19th, 2017) all the SSALTO/Duacs “all-sat-merged” products ( (M)SLA and (M)ADT Heights and geostrophic velocities (except the Mozambique area and climatologies) ) are disseminated by CMEMS. It is foreseen to stop the production of NRT products on Aviso+ by June 19th, 2017. Please if not already done, register on CMEMS as soon as possible. See below the list of products detailed in the tables with the end date of AVISO+ dissemination when necessary. 

What you will find in the AVISO+ reference portal in altimetry:

  • All the altimetry products are on the AVISO+ Catalogue (including those disseminated by CMEMS).
  • The gridded Sea Level products (MSLA-H, MSLA-UV, MADT-H and MADT-UV) can still be visualized with the Live Access Server (LAS).
  • AVISO+ keeps disseminating (see the tables below):
    • The Sea Level Anomalies climatologies for GlobalMediterranean Sea and Black Sea.
    • The Mozambique SLA-H, MSLA-H and MSLA-UV products with upgrades related to the new version, see below.
    • The gridded “two-sat-merged” Delayed-Time series. Note that this dataset is based on only two missions at most; it is mainly for applications in need of great temporal stability; they might not be the best in quality at a given time. In a near future, those products will be disseminated via the Copernicus Climate Change Service (C3S). AVISO+ will then stop the dissemination but will still propose these products in its catalogue.

List of the products concerned by the transition:

Click on the document Migration AVISO+ to CMEMS and C3S to display the hyperlinks for each product

April 19th new version:

The CMEMS version is called V3. The main changes are the following:

  • All the variables are delivered in a unique file (sla, adt, currents,… ) with new variable names,
  • The file nomenclature has changed,
  • New datasets are disseminated: Sentinel-3A (s3a) for NRT series and AltiKa Geodetic orbit called Drifting Phase (alg) , Jason-3 (j3) for REP (=REPROCESSING or Delayed-Time) series,
  • The MSS CNES_CLS15 is used instead of DTU13 for Arctic NRT series,
  • The extension of the REP series.

The complete description about this new CMEMS version (called V3) is available here, with details about each products in the dedicated CMEMS file where you will also find new files' samples. The altimetry products are referenced by the SEA LEVEL Thematic Assembly Center (SEA LEVEL TAC). 

The detailed information about AVISO+ dissemination is given below.

The Nomenclature of the CMEMS products dedicated to altimetry is:

SEALEVEL_<zone>_<variable>_<delay>_OBSERVATIONS_008_<xxx>    Where:

  • SEALEVEL stands for all SEA LEVEL TAC products
  • <zone>=GLO for global coverage, MED for Mediterranean Sea, BS for Black Sea, EUR for European region, ARC for Arctic Ocean
  • <variable>=PHY_L3 for SLA and ADT along-track products; PHY_ASSIM_L3 for SLA along-track products dedicated to assimilation; PHY_L4 for SLA, ADT and currents gridded-merged products
  • <delay>=NRT for near-real-time, REP for reprocessing (=delayed-time)
  • <xxx>= the number attributed to each product

Duacs 2014 Delayed-Time reprocessing

March 2014: Information about DUACS 2014 products changes and updates

On April 15th, 2014, a new version of the SSALTO/Duacs products distributed by Aviso, so-called DUACS 2014, will be released with several significant upgrades. The whole range of products, in near real time and delayed time, along track and gridded, will be impacted in terms of scientific content, format and naming. A complete reprocessing of the whole altimeter time series has also been performed. These evolutions have strong impacts and will necessitate actions on the user’s side.

These changes contribute to improve the product quality but also to better fit the users’ needs. They mainly concern:

  • The change of the reference period: in the DUACS 2014 version, the reference period of the Sea Level Anomalies is based on a 20-year [1993, 2012] period whereas in the former version it is on a 7-year [1993, 1999] period. 
  • The change of the SLA bias: the general convention to the bias applied to all of the SSALTO/DUACS SLA products consists of having a mean SLA null over the year 1993.
  • The evolution of the gridded product resolution and formats: a new Cartesian ¼° resolution is used instead of the 1/3° Mercator grid and a new NetCDF format with new variables is used. 
  • The evolution of the along track products geophysical content: a new processing is applied in terms of filtering and sub-sampling, inducing less smoothing notably at low latitudes and a denser dataset. 
  • In addition to these 4 main changes, several other scientific upgrades are applied. 

IMPORTANT NOTICE: the major upgrades of DUACS 2014 products, which are summarised in the table below, will have a strong impact and will necessitate actions on the user’s side. We encourage all SSALTO/Duacs users to carefully read the technical note which describes and explains these evolutions.

To insure a smooth transition between the current products and the DUACS 2014 products:

  • samples of DUACS 2014 products are already available in the dedicated operational ftp folders.
  • a double ftp dissemination is planned: the two versions of the products will be maintained up to mid June. 

The ftp access is already possible with the same personal username/password that you already have. Note that the ftp server has a new name since we changed by Aviso+ website: (the former one: is still working).

For any questions, please contact Aviso User Services: aviso(at) 

DUACS DT 2010 version
no more delivered
DUACS 2014 version
from April 15, 2014 onwards
Reference period for SLA (grid and along-track) 7-year period [1993, 1999] 20-year period [1993, 2012]
SLA bias convention - Mean SLA null over the year 1993
Spatial grid resolution and projection for the global product 1/3° Mercator 1/4° Cartesian with new grid points convention
Temporal grid resolution Daily maps in NRT
Weekly maps in DT
Daily maps in NRT and DT
Grid definition Latitude range for global product = [-82,82°N]
Longitude range for Mediterranean product= [355,396°E]
Latitude range for Global product= [-89.875,89.875°N]
Longitude range for Mediterranean product =[354.0625, 396.9375°E]
Grid NetCDF Standard NetCDF 3 Non CF NetCDF 3-CF, with new variables and attributes
Along track filtering for the Global product Low pass filtered with a cut-off wavelength between 65km and 250km depending on the latitude Low pass filtered with a cut-off wavelength of 65km for the whole globe
Along track sub-sampling for the global product 1 point kept over 3 to 7 points depending on the latitude 1 point kept over 2 points for the whole globe
Folders and file naming on server The Near Real Time and Delayed time product are respectively in the “nrt” and “dt” folders The Near Real Time and Delayed time product are respectively in the “near-real-time” and “delayed-time” folders and file nomenclature has changed

Further information:


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