Salinity impacts in the GMAO ocean data assimilation Chaojiao Sun

Experiments Assimilation method Forcing

GFDL 3D-VAR, Assimilating T only ODASIODASI-T OI, Assimilating T only ODASIODASI-TS OI, assimilating T and S ODASIGMAO-T OI, Assimilating T only GMAOGMAO-TS OI, Assimilating T and S GMAOGMAO-CTL No assimilation GMAO

Two GMAO schemes treat salinity differently: T – scheme: T assimilation only, S updates based on model T-S

relationship (Troccoli and Haines, 1999) TS – scheme: T and S assimilation (S comes from ARGO when

available, otherwise from Levitus climatology) Contributors: Michele Rienecker, Christian Keppenne, Jossy Jacob, Anna Borovikov (GMAO)Tony Rosati, Andrew Wittenburg, Matthew Harrison (GFDL)

TAO OBS

GMAO-CTL

ODASI-TS

GMAO-TS

ODASI-T

GMAO-T

GFDL analysis

T at 140°W(1993-2002)

TAO OBS

GMAO-CTL

ODASI-TS

GMAO-TS

ODASI-T

GMAO-T

GFDL analysis

U at 140°W(1993-2002)

Chaojiao Sun JCSDA Workshop April 20, 2005

1993-2002 average of U at 140°W

Chaojiao Sun JCSDA Workshop April 20, 2005

(Johnson et al., 2002)

1993-1998 Average(Ricci et al., 2005) 1993-2002 Average

Chaojiao Sun JCSDA Workshop April 20, 2005

(Johnson et al., 2002)

TAO servicing cruise tracks (meridional sections)

N. Niño 4(0°-5°N)

N. Niño 3(0°-5°N)

RMS T

RMS U

RMS S

RMS T

RMS S

RMS U

S. Niño 4(5°S-0°)

S. Niño 3(5°S-0°)

RMS T

RMS U

RMS S

RMS T

RMS S

RMS U

ECCO-GODAE project (1st year)

• Testing and porting MOM4 into the GMAO ocean model suite, and begin simulation

• Porting MOM4 in GMAO setting to JPL• Compare MOM4 results and data, including model error

calibration• Derivation of Kalman filter and smoother of MOM4 in

GMAO setting

Chaojiao Sun JCSDA Workshop April 20, 2005

Conclusions: TS scheme is effective in (1) correcting salinity bias in the model (2) constraining zonal current

1. Subsurface current structure – independent validation- GMAO compared well with TAO ADCPs (zonal structure on the EQ); GFDL compared well with Johnson’s data

(meridional structure)- sensitive to treatment of salinity – “TS” appears to be

effective

2. “TS” significantly improves subsurface salinity structure both zonally and meridionally, especially below the EUC core on the equator and in the northern Niñ0 3 & 4 regions; model bias is present in “T” scheme.

3. To effectively reduce salinity bias in the top 100-150m, satellite/in-situ salinity observations need to be assimilated

Ongoing work: treat surface salinity properly in “TS” investigate the impact of ARGO

assimilation

Chaojiao Sun JCSDA Workshop April 20, 2005

The End