Historical and Projected Changes in East African Meteorological

Historical and Projected Changes in East African Meteorological Drought Nathan Moore 1, 2, Dong-Yun Kim 3, Jeff Andresen 2, Sarah Hession 2 1 Zhejiang University 1 Michigan State University 3 Virginia Tech NSF Biocomplexity in the Environment Award 0709671

Long-Term Precipitation Changes Ve ry ari dr eg ion s • Long term changes are often masked by high interannual variability • Turkana Channel and Eastern Kenya: stronger lowlevel jet? IOD?

Long-Term Temperature Changes • No cooling anywhere • Broad spatial pattern: likely not assoc. with local forcings

Increasing Drought Frequency? Some results from Kim et al. (in prep) • Used Horvath Method: change point detection in a time series • Detects temporal discontinuities and timing • Horvath method is effective for changes in mean and/or variance

Drought Frequency: • Results from ERA 40 and CRU mostly match, although both rely on at least some of the same station data • Broad trends suggest increasing drought frequency across some southern sections and decreases across the north • Disagreements in SW Tanzania, Mt Kenya likely linked to changes in seasonality

10 A) Abrupt Rainfall change versus elevation. Kenya (mostly Mombasa to Kisumu); Tanzania 9 Horvath Score 8 7 6 5 R 2 = 0. 0645 4 More abrupt change with elevation? R 2 = 0. 458 3 2 1 Elevation (m) 0 0 500 1000 1500 2000 2500 1. 2 1 0. 8 Early Detection? R 2 = 0. 1938 0. 6 0. 4 Temperature change versus elevation. (Jarušková (1998) method) 0. 2 0 0 1000 2000

“Change Year” identified by Horvath Score Coincident with major oceanic circulation changes

Drought Frequency Transitions: normal rainfall to extreme drought From Kim et al. , in prep Frequency of transition from normal to ext. drought in a 6 -month period Worldclim

Changes in seasonality Historical: recent minus midcentury (CRU TS 2. 0) Projected: 2050 s minus current

Summary: • Climate has generally become warmer in East Africa during the last half century and wetter in some areas and drier in others • Future projections in East Africa need to focus on seasonality and variability changes • Changes in variability are more important than changes in mean for East African rainfall • Magnitude of some changes are correlated with elevation in many areas

Next Steps: • Integrate drought analysis with expanding marginal lands • Investigate socioeconomic effects resulting from changes in drought frequency

Next Steps: High Resolution Modeling 20 km grid 5 km grid 1. 2 km grid Mount Kenya Mount Kilimanjaro

Annual Precipitation A World. Clim CRU TS 2. 1 (mm/day), 1961 -1990