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 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 CLIVAR/VAMOS, Kousky/Halpert Features of South American Warm Season Rains

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

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

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 RegCMs have potential to improve spatial and temporal characteristics of seasonal rainfall characteristics Motivation

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

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 FMAM SST Anomalies

Workshop on Theory and Use of Regional Climate Models ICTP, Trieste June 2003 RegCM2: Giorgi et al., x145x14 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 Sensitivity to (Remote) Large Scale Forcing

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

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 Sensitivity to Local Forcing

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

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

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 Sensitivity to Domain

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

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.

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