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

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

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

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

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

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

8. 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 Motivation

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

11. Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003 FMAM SST Anomalies 1983 1985

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

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

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

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?

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

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

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

22. Sensitivity to Domain Is the local forcing sensitivity dependent on domain? Can a large domain improve the nested model simulation of the ITCZ?

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

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

27. Conclusions/Lessons Simulation: Large Scale Forcing is of 1 st 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.

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