11Supervisor: Eric Chassignet

Louis-Nicolas CARRIL MURTA

22

OutlineOutline

• MotivationMotivation• ARGO float systemARGO float system• HYCOMHYCOM• Data and model outputsData and model outputs• ComparisonComparison• ConclusionConclusion

33

MotivationMotivation

•Aim?Aim?

– To evaluate the performance of the To evaluate the performance of the global HYCOM ocean prediction global HYCOM ocean prediction systemsystem

– To improve the global HYCOM ocean To improve the global HYCOM ocean prediction systemprediction system

44

ARGO’s float ARGO’s float systemsystem

• Origin : WOCE Origin : WOCE 1990-19971990-1997

• Data transmitted by satelliteData transmitted by satellite

• Hydraulic system to descend Hydraulic system to descend till 2000m depthtill 2000m depth

• Provide a global quantitative Provide a global quantitative ocean variability, ocean variability, salinity, salinity, temperature, velocity with temperature, velocity with profilesprofiles

• Used for Used for model validationmodel validation

55

Float’s distributionFloat’s distribution

Lack of floats

66

• Hybrid model: combine 3 vertical discretizationsHybrid model: combine 3 vertical discretizations– z-level in unstratified regions like the mixed layerz-level in unstratified regions like the mixed layer– Density coordinates in stratified regionsDensity coordinates in stratified regions– Terrain-following coordinates in coastal regionsTerrain-following coordinates in coastal regions

• Solve oceanic physical processesSolve oceanic physical processes• Global 1/12° horizontal resolutionGlobal 1/12° horizontal resolution• Forced by NOGAPS, assimilation of observed T, Forced by NOGAPS, assimilation of observed T,

S, SSH S, SSH • Hindcast runs: velocities, temperature, salinityHindcast runs: velocities, temperature, salinity

HYCOMHYCOM Ocean Prediction System Ocean Prediction System

(HYbrid Coordinate Ocean Model)(HYbrid Coordinate Ocean Model)

77

ARGO data & HYCOM ARGO data & HYCOM outputsoutputs

•ARGO data :ARGO data :– Salinity & temperature :Salinity & temperature :

•From 2004 to 2007From 2004 to 2007

•Daily dataDaily data

•Profiles (scattered Profiles (scattered data)data)

– VelocityVelocity

•Mean from 1997 to Mean from 1997 to 20072007

•3°X3° rectilinear grid3°X3° rectilinear grid

•HYCOM outputs :HYCOM outputs :– Velocity, salinity and Velocity, salinity and

temperature :temperature :

•From 2004 to From 2004 to 20072007

•Daily outputsDaily outputs

•Global 1/12° Global 1/12° curvilinear gridcurvilinear grid

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HYCOM ARGO psu

°C

SALINITY SALINITY

TEMPERATURE TEMPERATURE

SURFACE TEMPERATURE AND SALINITY (2004-2007)

37

32

30

0

36

35

34

33

15

510

20

25

99

Surface U VelocitySurface U VelocityHYCOM ARGO

cm/s

2004-2007 average 1997-2007 average

20 15 10 5 -5 -10 -15 -200

1010

ComparisonComparison

•Global differences:Global differences:– Average of 2004 to 2007Average of 2004 to 2007– Seasonal averageSeasonal average

•Correlation (SST only):Correlation (SST only):– Monthly average linear regressionMonthly average linear regression

1111

2004-2007 (ARGO-HYCOM)2004-2007 (ARGO-HYCOM)°C & psu

TEMP SALINITY

TEMP SALINITY

Surface Surface

1000m 1000m

1.5

1

0.5

-0.5

-1

-1.5

-2

0

2

1212

Seasonal SST (ARGO-HYCOM)Seasonal SST (ARGO-HYCOM)

°C

Summer Fall

Winter Spring

1313

Coefficient of Linear Coefficient of Linear Regression Regression

~ 1

HYCOM & ARGO

correlated

~ 0

No correlation

~ -1

HYCOM & ARGO

opposite relationship

1414

ConclusionConclusion

• HYCOM global configuration provides HYCOM global configuration provides a good approximation of mean a good approximation of mean salinity, temperature and velocity for salinity, temperature and velocity for long time periodslong time periods

• But HYCOM appears to not But HYCOM appears to not accurately capture the monthly accurately capture the monthly variationsvariations

1515

1000 m U Velocity1000 m U VelocityHYCOM ARGO

cm/s

2004-2007 average 1997-2007 average

1616

SalinitySalinityHYCOM ARGO

Parking pressure 1000m

psu

1717

TemperatureTemperatureHYCOM ARGO

Parking pressure 1000m

°C