Statistical Analysis of Rainfall Pattern in Dire Dawa Eastern Ethiopia
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Date
2012-12
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Addis Abeba university
Abstract
This paper investigated the rainfall pattern of Dire Dawa, Eastern Ethiopia. Descriptive
Statistics, spectrum analysis, cross-spectral analysis as well as univariate Box-Jenkins
methodology to build Seasonal ARIMA model were used with the objective to analyze
rainfall pattern in Dire Dawa for the period from January, 1982-December, 2011 based
on data from Dire Dawa and adjacent stations: Dengego and Haramaya. Descriptive
Statistics result shows that the mean annual rainfall of Dire Dawa, Dengego and
Haramaya are 611mm, 774 mm and 772mm, respectively. The amount of rainfall at
Dengego and Haramaya are more or less the same on average in all seasons, and are
much higher than that of Dire Dawa over the study period. The variability of annual
rainfall in Dire Dawa during the last 30-year period is a bit larger than neighboring
station‟s rainfall (Dengego and Haramaya), indicating that climate instability is high in
Dire Dawa than other stations. A time series model for Dire Dawa station was adjusted,
processed, diagnostically checked and lastly an ARIMA (5, 0, 0)*(0, 1, 1)12 model is
established and this model is used to forecast two years monthly rainfall value. The
results indicate that relatively there is a tendency of increasing trend for forecasted
rainfall values. Spectrum analysis result showed that a rainfall extreme event recurs every
2.5 years in Dire Dawa. Further results indicated that rainfall pattern of Dengego and
Dire Dawa are found to be more related
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Keywords
Rainfall Pattern in Dire Dawa