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Simulating Rainfall Extremes in South America: Sensitivity to remote and local forcing

Simulating Rainfall Extremes in South America: Sensitivity to remote and local forcing. Anji Seth and Maisa Rojas International Research Institute for Climate Prediction. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003. South America: Population Density.

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Simulating Rainfall Extremes in South America: Sensitivity to remote and local forcing

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  1. Simulating Rainfall Extremes in South America: Sensitivity to remote and local forcing Anji Seth and Maisa Rojas International Research Institute for Climate Prediction Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  2. South America: Population Density • coastal populations • ecosystem diversity • arid Nordeste: 60% rural • Southeast: population • And economic center, • agricultural breadbasket Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  3. Features of South American Warm Season Rains CLIVAR/VAMOS, Kousky/Halpert Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  4. Motivation • Predictability exists, particularly in Nordeste Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  5. Rainfall anomalies in Nordeste, 1850-1995 Rainfall, SLP, Surface wind anomalies SST and Surface wind anomalies Wallace et al., 1998 Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  6. Motivation • Predictability exists, particularly in Nordeste • GCMs have good anomaly correlation skill in tropical South America Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  7. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  8. Motivation • Predictability exists, particularly in Nordeste • GCMs have good anomaly correlation skill in tropical South America • RegCMs have potential to improve spatial and temporal characteristics of seasonal rainfall characteristics Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  9. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  10. Outline • Simulation: FMAM 1983, 1985 • Sensitivity: Remote Forcing – Pacific/Atlantic SST • Sensitivity: Local Forcing – Amazon moisture • Sensitivity: Domain Effects – Boundary issues • Conclusions Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  11. FMAM SST Anomalies 19831985 Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  12. RegCM2: Giorgi et al., 1993 • 110x145x14 • 60 km resolution • Remote: • Reanalyses 83,85 • CCM3(x3) 83,85 • Local: deforestation Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  13. Sensitivity to (Remote) Large Scale Forcing Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

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  18. Sensitivity to Local Forcing The interior Amazon rainfall does not appear to be sensitive to SST forcing. Is the region more sensitive to local forcing? Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  19. Sensitivity to Local Forcing Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  20. Sensitivity to Local Forcing Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

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  22. Sensitivity to Domain • Is the local forcing sensitivity dependent on domain? • Can a large domain improve the nested model • simulation of the ITCZ? Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

  23. Sensitivity to Domain Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

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  27. Conclusions/Lessons • Simulation: Large Scale Forcing is of 1st order importance in determining the seasonal rainfall anomalies. Test the RegCM with more than one set of BCs • Sensitivity: Remote Forcing. Good anomaly correlation skill is necessary but not sufficient for GCMs. Low level winds and moisture are important. Know your GCM biases! • Sensitivity: Local Forcing appears to affect the regions upstream and downstream from the Amazon basin. Evidence suggests that Amazon deforestation can affect scales larger than were included in the CONTROL domain. Do deforestation studies require global high-res models? • Sensitivity: A large domain can potentially improve upon the GCM circulation, and showed the best seasonal evolution of rainfall. Place lateral boundaries where GCM has skill. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

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  29. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003

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