Salinity impacts in the GMAO ocean data assimilation Chaojiao Sun

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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

(Johnson et al., 2002)

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

(Johnson et al., 2002)

TAO servicing cruise tracks (meridional sections)

N. Niño 4(0°-5°N)

N. Niño 3(0°-5°N)

S. Niño 4(5°S-0°)

S. Niño 3(5°S-0°)

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

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

The End

Salinity impacts in the GMAO ocean data assimilation Chaojiao Sun

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