Hindcast Skill in SST Prediction in the new coupled NCEP Ocean-Atmosphere Model

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Hindcast Skill in the new coupled NCEP
Ocean-Atmosphere Model
E M C
Suranjana Saha, Wanqiu Wang, Hua-Lu Pan and the
NCEP/EMC Climate and Weather Modeling
Branch Environmental Modeling Center,
NCEP/NWS/NOAA Special Acknowledgements Sudhir
Nadiga, Jiande Wang, Qin Zhang, Shrinivas
Moorthi, Huug van den Dool
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Introduction A new global coupled
atmosphere-ocean model has recently been
developed at NCEP/EMC. Components a) the
T62/64-layer version of the current NCEP
atmospheric GFS (Global Forecast System) model
and b) the 40-level GFDL Modular Ocean Model
(version 3) Note Direct coupling with no flux
correction This model will replace the current
operational NCEP coupled model (CMP14) for SST
prediction in 2004.
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• Hindcast Skill Assessment
• 5-member ensemble over 22 years from 1981-2002
• January and April initial conditions
• Other months to follow
• 9 month runs
• Initial atmospheric states 0000 GMT 19, 20, 21,
  22, and 23 for each month
• Reanalysis-2 archive
• .
• Initial ocean states NCEP GODAS (Global Ocean
  Data Assimilation System) 0000 GMT 21st of each
  month
• Same for all runs
• GODAS operational September 2003

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• Hindcast Skill Assessment (cont)
• So far 220 runs have been made
• Hindcast skill
• Estimated after doing a bias correction for
  each year
• Uses model climatology based on the other years
• Anomaly correlation skill score for Nino 3.4
  region SST prediction
• Skill maps
• Global SST
• U.S. temperature and precipitation.
• Comparisons with CMP14 and CASST

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Observed
Coupled Red monthly bias
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• Composite Warm and Cold Events
• Events exceed ERSST variance by
• 1.0 SD (warm)
• 0.75 SD (cold)
• Heavy black line is mean

36 mo
- 36 mo
Peak
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SST Climatology on Equator
Red coupled model
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Ensemble Mean
CASST
CMP14
April IC
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CASST
Ensemble Mean
January IC
CMP14
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RMS Error April
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RMS Error January
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Observed
6 Month Lead (November) from April IC SST
anomaly for 1981-2002 Note Amplitudes
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Observed
6 Month Lead (August) from January IC SST
anomaly for 1981-2002 Note Amplitudes
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Hindcast Seasonally (3 month) Averaged SST
Anomaly Correlation April IC Note large
persistent skill in tropics
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Hindcast Monthly Averaged SST Anomaly
Correlation April IC June-September Left New
Coupled System Right CMP14
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Hindcast Monthly Averaged SST Anomaly
Correlation April IC October-January Left New
Coupled System Right CMP14
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Hindcast Seasonally (3 month) Averaged SST
Anomaly Correlation January IC Note large
persistent skill in tropics
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Hindcast Seasonally Averaged SST Anomaly
Correlation January IC Left New Coupled
System Right CMP14
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Hindcast 3 month Averaged U. S. Surface
Temperature Anomaly Correlation April IC Note
areas of persistent skill gt 60 at up to 6 month
lead
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U. S. Surface Temperature Hindcast Skill 3 Month
Averages April IC Comparison with CPC CCA Method
Note Coupled System skill complementary to CCA
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U. S. Surface Temperature Hindcast Skill 3 Month
Averages January IC Comparison with CPC CCA
Method Note Coupled System skill complementary
to CCA
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Hindcast 3 month Averaged U. S. Precipitation
Anomaly Correlation April IC Note areas of
persistent skill gt 60 at up to 6 month lead
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U. S. Precipitation Hindcast Skill 3 Month
Averages April IC Comparison with CPC CCA Method
Note Coupled System skill complementary to CCA
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U. S. Precipitation Hindcast Skill 3 Month
Averages January IC Comparison with CPC CCA
Method Note Coupled System skill complementary
to CCA
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MJO Forecasts (W. Wang)

• Experiments

• damp GFS03 with damped SST anomalies
• clim GFS03 with climatological SSTs
• amip GFS03 with observed SSTs
• coup CFS03 with MOM3 ocean analysis
• All forecasts to 45 days
• Composite results

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(Max pos. ampl. Over WPAC)
Phase 3
(Max pos. ampl. Over IO)
Phase 2
Phase 4
Phase 1
(Decay)
(Initiation)
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Days 1-30
Observed
SST Expt.
Damped
Climo
AMIP
Coupled
Note coupling necessary for propagation in
Phases 1-3
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Summary and Conclusions

• CFS03 hindcast skill for January and April
  initial conditions (1981-2002 ) have been
  evaluated
• For April, the SST AC skill over Nino 3.4 is
  better than CMP14 and CASST at all leads
• For January, the SST AC skill over Nino-3.4 is
  better than CMP14 and CASST for all leads, except
  lead 2

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Summary and Conclusions (cont)

• Ensemble mean forecasts for U.S. temperature and
  precipitation show comparable skill to CPCs CCA
  method.
• This skill is complementary to CCA as it
  manifests itself in different geographical areas
  and can be used in CPCs operational seasonal
  consolidated forecast.
• Hindcasts for the rest of the calendar months are
  being performed
• Implementation is being planned for late 2004

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New Climate Positions at NCEP/EMC

• UCAR Visiting Scientist Position at NCEP/EMC
• Work with NCEP Coupled Model
• http//www.earthworks-jobs.com/climate/ucar3101.ht
  ml
• NCEP Climate Team Leader (GS-15)
• Coordinate development activities with community
• Provide strategic guidance on NCEPs Climate
  Numerical Modeling activities
• Participate actively in development activities
  with EMC staff

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