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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)
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TAO OBS
GMAO-CTL
ODASI-TS
GMAO-TS
ODASI-T
GMAO-T
GFDL analysis
T at 140°W(1993-2002)
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TAO OBS
GMAO-CTL
ODASI-TS
GMAO-TS
ODASI-T
GMAO-T
GFDL analysis
U at 140°W(1993-2002)
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Chaojiao Sun JCSDA Workshop April 20, 2005
1993-2002 average of U at 140°W
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Chaojiao Sun JCSDA Workshop April 20, 2005
(Johnson et al., 2002)
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1993-1998 Average(Ricci et al., 2005) 1993-2002 Average
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Chaojiao Sun JCSDA Workshop April 20, 2005
(Johnson et al., 2002)
TAO servicing cruise tracks (meridional sections)
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N. Niño 4(0°-5°N)
N. Niño 3(0°-5°N)
RMS T
RMS U
RMS S
RMS T
RMS S
RMS U
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S. Niño 4(5°S-0°)
S. Niño 3(5°S-0°)
RMS T
RMS U
RMS S
RMS T
RMS S
RMS U
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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
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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
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Chaojiao Sun JCSDA Workshop April 20, 2005
The End