Decadal Temperature, Rainfall and Hydrological Trends Over the Greater Horn of Africa

This study investigates decadal trends of temperature, rainfall and river discharge over the Greater Horn of Africa (GHA) through the diagnosis of observations and General Circulation Model (GCM) output. In the recent decades (1979-2001), observations suggest northern GHA is becoming increasingly wetter while southern GHA is becoming drier. Intraseasonal variability of the observed trend depicts a complex spatial distribution of the rainfall anomalies with the tendency for October to be the largest contributor to the rainfall anomaly trend. Model rainfall diagnostics from NCAR Community Atmosphere model version 2.0.1 suggests that the increasing trend in the recent decades may be representative of a quasi-decadal trend over GHA. Trends from the Blue Nile and White Nile Rivers also indicate decadal climate variability since the early 1910s. The projected rainfall from NCAR/NASA-CCM3 A2 scenario suggest a dipole like change in the rainfall anomalies with maximum precipitation change centered over Lake Victoria. As for temperature, observed and model seasonal mean surface temperatures generally show a warming trend since the 1960s. Projected surface temperatures suggest substantial temperature increase over GHA exceeding 3.5°C in higher elevations.