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Coupled Ocean-Atmosphere Response to North Tropical Atlantic SST: Tropical Atlantic Dipole, NAO and ENSO

Coupled Ocean-Atmosphere Response to North Tropical Atlantic SST: Tropical Atlantic Dipole, NAO and ENSO. Lixin Wu Physical Oceanography Laboratory Ocean University of China Qingdao, China. Collaborators: Feng He and Zhengyu Liu

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Coupled Ocean-Atmosphere Response to North Tropical Atlantic SST: Tropical Atlantic Dipole, NAO and ENSO

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  1. Coupled Ocean-Atmosphere Response to North Tropical Atlantic SST: Tropical Atlantic Dipole, NAO and ENSO Lixin Wu Physical Oceanography Laboratory Ocean University of China Qingdao, China Collaborators: Feng He and Zhengyu Liu Center For Climatic Research, University of Wisconsin-Madison

  2. Motivations Questions: Are there anythings remaining elusive? Are there anythings missing in this diagram

  3. Dong and Sutton 2002 Atlantic-Tropical Pacific Teleconnection in Recent Water-Hosing Experiments: Zhang and Delworth 2005 cooling warming

  4. Questions: • Is tropical Atlantic dipole an internal dynamic mode? • How does the tropical Atlantic affect the extratropical North Atlantic, particular in different seasons? • How does the North Atlantic SST affect the tropical Pacific?

  5. Outline • Motivations • Model and Experiments • Tropical Atlantic Response • Extratropical North Atlantic Response • Tropical Pacific Response • Summary and Conclusions

  6. Model and Experiments Fast Ocean Atmosphere Model (FOAM) • Atmosphere: CCM2 (dynamics) + CCM3 (physics) R15+19 levels (FOAM1.5) • Ocean: MOM-like 2.8ox1.4o x32 levels

  7. Model Tropical Climatology JJA DJF Annual

  8. Coupled Modeling exploring:

  9. Tropical Atlantic Response

  10. MAM Wind and Heat Flux and SST JAS Wind and Flux and SST

  11. IV Approach PC Approach

  12. Forcing in the South Atlantic MAM SST, Wind and Flux

  13. Suggestions: • The tropical dipole mode is an internal coupled mode, with a maximum in Spring season • The coupled ocean-atmosphere interaction in the tropical Atlantic is controlled by the WES feedback and seasonal migration of the mean ITCZ

  14. Extratropical North Atlantic Response

  15. Horseshoe FMA JJA FMA JJA Tripole OND FMA OND FMA

  16. FMA MJJ FMA Z500 Z500 OND JFM OND

  17. North Tropical Atlantic can • In late winter, force an NAO-like reponse in the extratropical Atlantic, and a dipole SST in the extratropics. • In summer, force a northward Rossby wavetrain to Europe and a horseshoe-like SST pattern • In the fall to next winter, force a NAO-like reponse (the sign as the previous winter) and a dipole

  18. Tropical Pacific Response

  19. FMA JJA OND

  20. SST, surface wind, heat flux averaged over <10S,10N>

  21. F FMA SST, SLP,wind,heat flux Z500, Precip.

  22. Predictability FM JJA OND

  23. South Atlantic Forcing FMA JJA OND

  24. Summary • Tropical Atlantic O/A interaction is regulated by WES feedback and seasonal migration of the ITCZ. The tropical Atlantic dipole is an internal dynamic mode, but occurs only in spring season. • Tropical Atlantic SST plays an important role in modulating extratropical Atlantic climate. NTA SST(late winter)->NAO->NTA SST(summer) ->horseshoe(summer and fall) ->NAO(next winter) ->extratropical dipole • The tropical north Atlantic SST can force a dipole-like SST in the eastern tropical Pacific, that can subsequently evolve into an ENSO-like pattern.

  25. Thank you Physical Oceanography Lab. Ocean University of China Tsingdao, China

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