vague
ENACT
CLS TASKS
The RIO-03 Combined Mean Dynamic Topography (CMDT)
 
The direct method
The synthetic method
CMDT versus OCCAM, Levitus and Le Grand
CMDT RIO-03 References
 





  Comparison of Global Mean Dynamic Topographies

 
  • Global comparison

The CMDT RIO-03 (righ bottom) is compared to 3 other MDT: the Levitus Climatology (left bottom), the OCCAM  model (mean from 1993-1995, left top) and the Le Grand inverse model solution (right top):

 
Four Mean Dynamic Topographies

 

 

The Levitus and Legrand MDT are too smooth. Levitus have poor realism in Arctic and Antarctic areas. The OCCAM and RIO-03 MDT compare better:

OCCAM - RIO MDT

Le Grand - RIO MDT

Levitus - RIO MDT

Scales of height differences in cm

 

To exactly quantify the differences, the four MDT have then been compared more carefully in four areas, using drifter velocities:

  • AGHULAS current
 

  SVP drifters in 2001 in the Aghulas Current

OCCAM

17.7 cm/s
17.0cm/s
Cv: 0.75

Le Grand

16.9 cm/s
17.1 cm/s
Cv: 0.75

Levitus

17.3 cm/s
16.8 cm/
Cv: 0.75

CMDT RIO-03

15.9 cm/s
16.3 cm/s
Cv: 0.78

 

Altimetric anomalies of geostrophic velocities are added to each MDT, in order to produce the full ocean currents, then compared to concurrent drifter velocities. Differences (in rms) are due to smoothing differences between altimetry and lagrangian data, noise in each data set, and MDT errors. Because we use exactly the same set of data, the lowest differences correspond to the more precise MDT. Vectorial correlation are also computed (Cv).

 
  • KUROSHIO area
 

  SVP drifters in 2001 in the Kuroshio area

OCCAM

14.0 cm/s
14.1 cm/s
Cv: 0.67

Le Grand

14.7 cm/s
15.1 cm/
Cv: 0.64

Levitus

14.4 cm/s
14.7 cm/
Cv: 0.64

CMDT RIO-03

13.7 cm/s
14.2 cm/s
Cv: 0.68

 
  • GULF STREAM area
  •  

      SVP drifters in 2001 in the Gulf Stream area    

    OCCAM

    19.5 cm/s
    18.2 cm/s
    Cv: 0.66

    Le Grand

    19.6 cm/s
    18.1 cm/
    Cv: 0.65

    Levitus

    20.4 cm/s
    18.3 cm/
    Cv: 0.62

    CMDT RIO-03

    18.1 cm/s
    17.4 cm/s
    Cv: 0.70

     

    Differences are particularly high in the Gulf Stream area were currents are intense, and differences between drifter velocity and satellite altimetric deduced velocities are larger.

     
    • DRAKE FALKLAND area
     
    Comparison in the Falkland Current area

      SVP drifters in 2001 in the Drake-Falkland area

    OCCAM

    14.0 cm/s
    14.5 cm/s
    Cv: 0.68

    Le Grand

    14.3 cm/s
    15.4 cm/
    Cv: 0.64

    Levitus

    14.8 cm/s
    16.6 cm/
    Cv: 0.60

    CMDT RIO-03

    13.3 cm/s
    13.7 cm/s
    Cv: 0.72

     

    The direct method
    The synthetic method
    CMDT versus OCCAM, Levitus and Le Grand
    CMDT RIO-03 References
    Copyright © 1999-2004 CLS. All rights reserved. Latest Update: 10/02/2004