Supervisor: Eric Chassignet Louis-Nicolas CARRIL MURTA Supervisor: Eric Chassignet
Outline Motivation ARGO float system HYCOM Data and model outputs Comparison Conclusion
Motivation Aim? To evaluate the performance of the global HYCOM ocean prediction system To improve the global HYCOM ocean prediction system
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
Float’s distribution Lack of floats
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
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
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 (2004-2007)
Surface U Velocity HYCOM ARGO cm/s 2004-2007 average 1997-2007 average 15 10 5 -5 -10 -15 -20 cm/s
Comparison Global differences: Correlation (SST only): Average of 2004 to 2007 Seasonal average Correlation (SST only): Monthly average linear regression
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
Seasonal SST (ARGO-HYCOM) Summer Fall Spring Winter °C
Coefficient of Linear Regression HYCOM & ARGO opposite relationship a ~ 0 No correlation a ~ 1 HYCOM & ARGO correlated
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
1000 m U Velocity HYCOM ARGO 2004-2007 average 1997-2007 average cm/s
Salinity HYCOM ARGO Parking pressure 1000m psu
Temperature HYCOM ARGO Parking pressure 1000m °C