Combined mean dynamic topography - MDT CNES-CLS22

Types of dataset: auxiliary products

DOI: 10.24400/527896/a01-2023.003 - more metadata

Contents: The Mean Dynamic Topography MDT-CNES-CLS22 is an estimate of the mean over the 1993-2012 period of the sea surface height above geoid. This is consistent with the reference time period also used in the SSALTO DUACS products.

Use: ocean circulation, operational oceanography

Description: use of the latest GOCO06S geoid model (based on the complete GOCE mission fully reprocessed and 14 years of GRACE data) and 30 years of altimetry and in-situ data (hydrologic, drifters and High Frequency radar on a limited area). (More information)

Geographic coverage: global, 1/8°

Distribution media: Authenticated FTP, gridded data extraction tool and Thredds Data Server (TDS).

Condition of access: The MDT-CNES-CLS22 is a standard product as stated in the licence agreement. Please see our FAQ to access this product (distinction if you are already an Aviso+ user or not).

Copyright: 1992-ongoing Cnes-CLS

References:
- Jousset S., Mulet S., Wilkin J., Greiner E., Dibarboure G. and Picot N.: “New global Mean Dynamic Topography CNES-CLS-22 combining drifters, hydrological profiles and High Frequency radar data”, OSTST 2022, https://doi.org/10.24400/527896/a03-2022.3292.
- Image of the month March 2022: a new mean dynamic topography released

to get access Aviso products and select the product "MDT_CNES_CLS (Global Mean Dynamic Topography)"

MDT

Product	Authenticated access service	type	format	File weight
MDT-CNES-CLS22	access via MY AVISO+ and select the product "MDT_CNES_CLS (Global Mean Dynamic Topography)"	gridded	NetCDF4	48 Mb

Releases of previous MDT

MDT-CNES-CLS18

All information about this MDT can be found in a dedicated page.

MDT_CNES-CLS13 improvements are:

In the computation of the first-guess:
- use of the geoid model EGM-DIR-R4 based on 2 years of reprocessed GOCE data and 7 years of GRACE data
- use of the CNES-CLS11 Mean Sea Surface
- improvement of the filtering process
- optimal filter at around 125 km (instead of about 400 km)
In the combination with oceanic in-situ data:
- updated dataset of drifting buoy velocities (1993-2012) and carefully preprocessed to take into account drogue loss and corrected for wind slippage in this case
- Improvement of Ekman model to extract the geostrophic component of the buoy velocities (parameters fitted over the 1993-2012 period, by longitude, latitude and month) and computation of an Ekman model at 0m (used for undrogued boys) and at 15m depth (used for drogued boys)
- updated dataset of dynamic heights (1993-2012) computed from Temperature/Salinity profiles from CORA3.4

Comparison between MDT CNES-CLS13 and MDT09 can be found in a dedicated page.
Details about MDT CNES-CLS13 can be found here.

CNES-CLS09_v1.1

Contents: mean of the 1993-1999 period sea surface above geoid, corrected from geophysical effects. The MDT_CNES-CLS09 is an estimate of the ocean MDT for the 1993-1999 period. The MDT for a different time period P can be easily deduced using altimetric Sea Level Anomalies referenced to the 1993-1999 period with : MDT_P=MDT_93-99+<SLA_93-99>_P. The Ssalto/Duacs multimisson (M)ADT products from the Duacs 2014 (V15.0) are computed with a new MDT referenced over a twenty-year period [1993-2012] which doesn't correspond to this MDT CNES-CLS09.
Description: based on 4.5 years of GRACE data, and 15 years of altimetry and in-situ data (hydrologic and drifters data). (More information).

The strongest changes with the CNES-CLS09_v1.0 concern the mean velocity estimate in the equatorial band: due to the failure of the geostrophic approximation near the equator, no velocity estimates were given in the CNES-CLS09_v1.0 release for the [-3°,3°] latitudinal band. A specific work has been done to estimate the mean velocities at the equator.

Figure 1: Mean velocity module (in cm/s) in the [-15°, 15°] latitudinal band in the CNES-CLS09_v1.0 release (top) and in the CNES-CLS09_v1.1 release (bottom).

The height differences between the two releases is small with a global mean difference of -0.02 cm and a rms difference of 0.05 cm.

CNES-CLS09_v1.0.

Compared to the previous RIO05 field, the main improvements are:

The use of the recent EIGEN-GRGS.RL02.MEAN-FIELD based on 4,5 years of GRACE data
The use of an updated dataset of drifting buoy velocities(1993-2008)and dynamic heights(1993-2007)
The use of an improved Ekman model to extract the geostrophic component of the buoy velocities
The use of an improved processing method of the dynamic heights allowing to make use of T/S profiles to different reference depths.
Estimation was done on a 1/4° resolution grid(instead of 1/2° for RIO05).