Hindcast Skill in the new coupled NCEP Ocean-Atmosphere Model

1. 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

2. 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.

3. 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

4. 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

5. Observed Coupled Red: monthly bias

6. 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

7. SST Climatology on Equator Red: coupled model

8. Ensemble Mean CASST CMP14 April IC

9. CASST Ensemble Mean January IC CMP14

10. RMS Error April

11. RMS Error January

12. Observed 6 Month Lead (November) from April IC SST anomaly for 1981-2002 Note Amplitudes

13. Observed 6 Month Lead (August) from January IC SST anomaly for 1981-2002 Note Amplitudes

14. Hindcast Seasonally (3 month) Averaged SST Anomaly Correlation April IC Note: large & persistent skill in tropics

15. Hindcast Monthly Averaged SST Anomaly Correlation April IC June-September Left: New Coupled System Right: CMP14

16. Hindcast Monthly Averaged SST Anomaly Correlation April IC October-January Left: New Coupled System Right: CMP14

17. Hindcast Seasonally (3 month) Averaged SST Anomaly Correlation January IC Note: large & persistent skill in tropics

18. Hindcast Seasonally Averaged SST Anomaly Correlation January IC Left: New Coupled System Right: CMP14

19. Hindcast 3 month Averaged U. S. Surface Temperature Anomaly Correlation April IC Note: areas of persistent skill > 60% at up to 6 month lead

20. U. S. Surface Temperature Hindcast Skill 3 Month Averages April IC Comparison with CPC CCA Method Note: Coupled System skill complementary to CCA

21. U. S. Surface Temperature Hindcast Skill 3 Month Averages January IC Comparison with CPC CCA Method Note: Coupled System skill complementary to CCA

22. Hindcast 3 month Averaged U. S. Precipitation Anomaly Correlation April IC Note: areas of persistent skill > 60% at up to 6 month lead

23. U. S. Precipitation Hindcast Skill 3 Month Averages April IC Comparison with CPC CCA Method Note: Coupled System skill complementary to CCA

24. U. S. Precipitation Hindcast Skill 3 Month Averages January IC Comparison with CPC CCA Method Note: Coupled System skill complementary to CCA

25. 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

26. (Max pos. ampl. Over WPAC) Phase 3 (Max pos. ampl. Over IO) Phase 2 Phase 4 Phase 1 (Decay) (Initiation)

27. Days 1-30 Observed SST Expt. Damped Climo AMIP Coupled Note: coupling necessary for propagation in Phases 1-3

28. 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

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

30. 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.html • NCEP Climate Team Leader (GS-15) • Coordinate development activities with community • Provide strategic guidance on NCEP’s Climate Numerical Modeling activities • Participate actively in development activities with EMC staff