Products
Combined mean dynamic topography
Types of dataset: auxiliary products
Contents: mean of the 1993-1999 period sea surface above geoid, corrected from geophysical effects
Use: ocean circulation, operational oceanography
Description: based on 4.5 years of GRACE data, and 15 years of altimetry and in-situ data (hydrologic and drifters data). (More information).
Geographic coverage: global
Format: ASCII, NetCDF
Distribution media: FTP
Condition of access: All auxiliary product users need an account, see Access to auxiliary products.
To get an acces to the last version of MDT product, please fill in, select the given product (on the second page of the form) and valid the following form:
Warning : 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 : MDTP=MDT93-99+<SLA93-99>P
File weight: 64 MB (Ascii) et 56 MB (NetCDF)
How to cite Aviso data?
Copyright: 1992-ongoing Cnes-CLS
Releases of MDT
March 2010: CNES-CLS09_v1.1
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.
- Figure 2: Map of height differences (in cm) between the CNES-CLS09_v1.0 MDT and the CNES-CLS09_v1.1 MDT
October 2009: 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).