1. A Recent Abrupt Decline in the East African Long Rains Bradfield Lyon and David G. DeWitt Presented by: Tufa Dinku tufa@iri.columbia.edu International Research Institute for Climate and Society The Earth Institute at Columbia University A Recent Abrupt Decline in the East African Long Rains Bradfield Lyon and David G. DeWitt Presented by: Tufa Dinku tufa@iri.columbia.edu International Research Institute for Climate and Society The Earth Institute at Columbia University

2. Outline The DeclineThe Decline The Driver(?)The Driver(?) Modeling experimentModeling experiment

3. Rainfall Decline: Regional CAMS_OPI (mm/day) anomaly for Mar-May 2011 CMAP Mar-May(1999-2010 average) anomaly (from 1979- 2010 mean) Mar-May total RR, averaged over (10S-12N, 30-53E) Box..

4. Apr-May PRCP (1998-2008) – (1979-1996) CMAP GPCP

5. Rainfall Decline: Ethiopia

6. Annual Rainfall, country average from different number of stations

7. Spatial Rainfall pattern Weights for leading mode(16.3% of VAR) of March-May precipitation obtained from EOF analysis of CAMS_OPI data for 1979-2011 Principal component time series for March- May leading mode

8. What is the driver? March-May SST anomaly averaged from 1999-2011, expressed as a standardized departure from the 1971- 2000 mean Loadings for the 2nd mode of March-May SST based on an EOF analysis for the period 1950-2011. Principal component time series (1950-2011)

9. The Driver: The Driver: East Africa April-May Rainfall Index and Tropical SST Correlation (1979-2010)

10. Modeling

11. Modeling Experiment a.Multi-model ensemble mean (72 members) MAM RR anomaly (mm/day) from simulations using observed SSTs, averaged over1999-2009. a. Ensemble mean (24 members) ECHAM5 precipitation anomaly (mm/day) from idealized runs forced with observed March-May SST anomalies averaged over 1999-2010 for the tropical Indian Ocean only. b.As in b, but for model runs forced with SSTs only for the tropical Pacific. Top legend only for a); bottom legend for b and c.