Mobile version

The Combined Mean Dynamic Topography (CMDT)

Combined Mean Dynamic Topography MDT_CNES-CLS13. Credits CNES-CLS.

The point of estimating a global Mean Dynamic Topography (MDT) is to reference the altimeter Sea Level Anomalies (SLA), computed relative to a 20 year (1993-2012) mean profile, in order to obtain absolute measurements of the ocean dynamic topography.
Required MDT has to be consistent with altimeter physical content and shall therefore correspond to the mean over 1993-2012 of both the barotropic and baroclinic components of the ocean absolute dynamic topography. 

Note that the Ssalto/Duacs (M)SLA products are computed relative to 1993-2012 period since April 2014 (Duacs 2014 v15.0 version). Thus it is mandatory to be consistent and use (M)SLA and MDT referenced to the same time period. Further information on the change of the altimeter reference period.

The MDT_CNES-CLS13 calculation combines several steps:

  • We first use a direct method to estimate at large scale a MDT using the Mean Sea Surface MSS_CNES-CLS11 and the EGM-DIR-R4 geoid model (this model is based on 2 years of reprocessed GOCE data and 7 years of GRACE data).
  • Then we use a synthetic method where sea level anomalies are subtracted from in-situ measurements of the ocean state (dynamic heights over the 1993-2012 period and geostrophic surface velocities over the 1993-2012 period) to compute synthetic estimates of the MDT and the corresponding mean geostrophic surface velocities. 
  • Then, using a multivariate objective analysis, the synthetic estimates of mean heights and mean velocities are used to improve the first guess of the MDT. It's the calculation of the CMDT (Combined Mean Dynamic Topography).
  • Finally, a validation is done by comparing the MDT_CNES-CLS13 with others MDT: CNES-CLS09, Rio05, Maximenko et al. 2009, Glorys1V1 and DNSC.
Calculation method for MDT_CNES-CLS13.
Rss feedsContactSitemapPartnersFAQGlossaryLexiconMobile
You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

The new home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!