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Ref20yto7y: change of the altimeter reference period

New reference period: In the Duacs 2014 version (v15.0), the reference period of the Sea Level Anomalies is based on a 20-year [1993, 2012] period whereas in the former version it was on a 7-year [1993, 1999] period.

To allow the users to ensure this consistency between the (M)SLA and MDT products, new "ref20yto7y" products are added to the catalogue. They consist of corrective maps that allow the user to change the reference period of the (M)SLA and MDT products from 20 years to 7 years. Depending on your application, you may wish to use this improved 20-year reference or you may wish to keep the original 7-year reference period. Further information: How to manage the change?

This corrective map is available for Global area, Mediterranean and Balck Seas (see below). For the another areas (Arctic Ocean, Mozambique and Europe areas) you have to use the global corrective map.

How to manage the change?

This corrective product can be used in two ways:

  • 1st corrective method, change the (M)SLA reference period:
    Users can apply the corrective map to the new DUACS 2014 (M)SLA fields referenced to the 20-year period (SLA_20y) in order to obtain a (M)SLA referenced to the original 7-year period (SLA_7y). The obtained (M)SLA is equivalent to the former DUACS products. When working with along-track measurements, you need to interpolate the gridded variable ref20yto7y onto the location of the SLA_20y measurements.
SLA_7y = SLA_20y – ref20yto7y
  • 2nd corrective method, change the MDT reference period:
    This corrective term can also be applied to the static MDT field:
MDT_20y = MDT_7y – ref20yto7y

In any case, the (Maps of) Absolute Dynamic Topography field will be unchanged if you use consistent (M)SLA and MDT products. Check that you compute it in a consistent way using the new 20-year reference period:

ADT = SLA_20y + MDT_20y

Or the 7 year reference period:

ADT = SLA_7y + MDT_7y

Global Ref20yto7y

SatelliteAuthenticated access service
FrequencyData periodFile weight
MergedFTPone shotno time resolution1 Mo
Global Ref20yto7y product: Corrective map to change the reference period of the (M)SLA and MDT products from 20 years to 7 years (to download through FTP). Credits CLS/Cnes.

Mediterranean Ref20yto7y

SatelliteAuthenticated access service
FrequencyData periodFile weight
MergedFTPone shotno time resolution1 Mo
Mediterranean Ref20yto7y product: Corrective map to change the reference period of the (M)SLA and MDT products from 20 years to 7 years(to download through FTP). Credits CLS/Cnes.

Black Sea Ref20yto7y

SatelliteAuthenticated access service
FrequencyData periodFile weight
MergedFTPone shotno time resolution1 Mo
Black Sea Ref20yto7y product: Corrective map to change the reference period of the (M)SLA and MDT products from 20 years to 7 years (to download through FTP). Credits CLS/Cnes.
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