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The Impacts of the Indian Ocean warming trend on African Climate.

The Impacts of the Indian Ocean warming trend on African Climate. Dan Hodson and Rowan Sutton. NCAS Centre for Global Atmospheric Modelling Department of Meteorology University of Reading. Outline. Observations. Experiments I Atmosphere model forced with:

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The Impacts of the Indian Ocean warming trend on African Climate.

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  1. The Impacts of the Indian Ocean warming trend onAfrican Climate. Dan Hodson and Rowan Sutton NCAS Centre for Global Atmospheric Modelling Department of Meteorology University of Reading

  2. Outline • Observations. • Experiments I • Atmosphere model forced with: • Historical Observed Sea Surface Temperatures. • 1°C Anomaly in the Indian Ocean • Indian Ocean Temperature Trend • Experiments II • Atmosphere model force with Observed Indian Ocean warming Trend • Results • Conclusions and Caveats

  3. Observations

  4. 1950-1999 Trend in Rainfall Hoerling et al. J. Climate 2006

  5. Experiments I

  6. AGCM forced with Observed SSTs

  7. FMA AGCM Forced with Obs SSTs 1950-1999 Hoerling et al. J. Climate 2006

  8. JAS AGCM Forced with Obs SSTs 1950-1999 Hoerling et al. J. Climate 2006

  9. AGCM forced with 1°C Indian Ocean

  10. +1°C

  11. AGCM Forced with 1C Indian Ocean Anomaly

  12. AGCM Forced with 1C Indian Ocean Anomaly

  13. Indian Ocean Temperature Trend

  14. Indian Ocean SST Trend C

  15. Indian Ocean SST trend 0.02 -0.02 Annual mean SST trend 1951-1990 C/year

  16. Atmosphere model force with Observed Indian Ocean warming Trend

  17. SST Anomalies Sept May Jan

  18. Indian Ocean SST Trend IOP ION C

  19. Experiment • Five AGCMs • Arpege • CAM3 • Echam5 • GAM (IAP) • HadAM3 • Indian Ocean Positive (IOP) • Indian Ocean Negative (ION)

  20. Results

  21. Vertical velocity Rainfall Surface Temperature ARP CAM ECH GAM HAD FMA

  22. Vertical velocity Rainfall Surface Temperature ARP CAM ECH GAM HAD JAS

  23. Caveats?

  24. Observed MSLP trends Copsey et al GRL 2006

  25. MSLP Trends

  26. Conclusions • AGCMs forced with warm Indian Ocean capture some of the trends in African rainfall (both FMA and JAS). • Trends associated with changes in subsidence/ changes in Walker Circulation. • Can we use AGCMs to model past changes in this way?

  27. Vertical Structure JAS

  28. Vertical Structure FMA

  29. Station rainfall trends 1950-1999 (JAS/FMA)

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