Ethiopia is one of the countries whose economy is highly dependent on rain-fed agriculture and is also facing recurring cycles of flood and drought. Climate variability imposes a significant challenge in the country. Consequently, this paper intends to predict the frequency of extreme rainfall in Eastern Ethiopia. Descriptive statistics, and spectrum analysis were used for analyzing 71 year annual rainfall data obtained from Ethiopian meteorological agency, from synoptic station of Dire Dawa ,Harar and JigJiga region. The amounts of rainfall at Dire Dawa and JigJiga are more or less the same on average in all seasons, and are much higher than that of Harar over the study period. However, variability of annual rainfall in JigJiga region during the past 71-year period is higher than neighboring region rainfall (Dire Dawa and Harar), indicating that climate instability is high in JigJiga than others. Spectral peak with periodicity of 4.17 year was statistically significant in the rainfall of Dire Dawa region. However, there is no evidence of significance spectral peak in the rainfall of Harar and JigJiga region. It can be inferred that rainfall extreme event recurs at every 2.33 years in Harar and 4.17 years in Dire Dawa and JigJiga regions. Based on the result in the observed periodicity of flood and drought, future climate change and weather extremes can be managed by reducing the magnitude of economic, social and human damage, which will eventually lead to better resistance.
Keywords: Extreme event, variability, periodicities, spectral analysis.