1. Supervisor: Eric Chassignet
Louis-Nicolas CARRIL MURTA
Supervisor: Eric Chassignet

2. Outline Motivation ARGO float system HYCOM Data and model outputs
Comparison
Conclusion

3. Motivation
Aim?
To evaluate the performance of the global HYCOM ocean prediction system
To improve the global HYCOM ocean prediction system

4. ARGO’s float system Origin : WOCE 1990-1997
Data transmitted by satellite
Hydraulic system to descend till 2000m depth
Provide a global quantitative ocean variability, salinity, temperature, velocity with profiles
Used for model validation

5. Float’s distribution
Lack of floats

6. HYCOM Ocean Prediction System
(HYbrid Coordinate Ocean Model)
Hybrid model: combine 3 vertical discretizations
z-level in unstratified regions like the mixed layer
Density coordinates in stratified regions
Terrain-following coordinates in coastal regions
Solve oceanic physical processes
Global 1/12° horizontal resolution
Forced by NOGAPS, assimilation of observed T, S, SSH
Hindcast runs: velocities, temperature, salinity

7. ARGO data & HYCOM outputs
Salinity & temperature :
From 2004 to 2007
Daily data
Profiles (scattered data)
Velocity
Mean from 1997 to 2007
3°X3° rectilinear grid
HYCOM outputs :
Velocity, salinity and temperature :
From 2004 to 2007
Daily outputs
Global 1/12° curvilinear grid

8. HYCOM ARGO psu 37 36 35 34 33 32 °C 30 25 20 15 10 5 SALINITY SALINITY
TEMPERATURE
TEMPERATURE 25 20 15 10 5
SURFACE TEMPERATURE AND SALINITY ( )

9. Surface U Velocity HYCOM ARGO cm/s 2004-2007 average 1997-2007 average15 10 5 -5
-10
-15
-20
cm/s

10. Comparison Global differences: Correlation (SST only):
Average of 2004 to 2007
Seasonal average
Correlation (SST only):
Monthly average linear regression

11. 2004-2007 (ARGO-HYCOM) °C & psu 2 Surface Surface SALINITY TEMP 1.5 1
0.5
1000m
1000m
TEMP
SALINITY
-0.5 -1
-1.5 -2

12. Seasonal SST (ARGO-HYCOM)
Summer
Fall
Spring
Winter °C

13. Coefficient of Linear Regression
HYCOM & ARGO
opposite relationship
a ~ 0
No correlation
a ~ 1
HYCOM & ARGO
correlated

14. Conclusion
HYCOM global configuration provides a good approximation of mean salinity, temperature and velocity for long time periods
But HYCOM appears to not accurately capture the monthly variations

15. 1000 m U Velocity
HYCOM
ARGO
average
average
cm/s

16. Salinity
HYCOM
ARGO
Parking pressure 1000m
psu

17. Temperature
HYCOM
ARGO
Parking pressure 1000m °C