The effect of El Niño-Southern oscillation (ENSO) on the Ethiopian Rainfall Pattern
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Date
2012-06
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Addis Ababa University
Abstract
This study is focused on the first step to investigate the interdependence between El Niño-Southern Oscillation (ENSO) and the rainfall pattern in the Ethiopian diverse micro-climate zones, using correlation and spectrum analysis. For this purpose, the sea surface temperature in the pacific and the measured rainfall in the diverse micro-climate zones have been used as parameters. The investigation was made by filtering the desired data and then directly correlating long period data both in time and frequency domain. The correlation analysis in the time domain on one hand showed that the rainfall in most locations in the north western, north east and central part of Ethiopia have a strong negative correlation with ENSO. The average time lag for these negatively correlated values is found to be 4 to 12 months after the occurrence of ENSO. On the other hand some few locations in the south and south eastern parts of Ethiopia showed very weak positive correlation. The result from the spectrum analysis also showed that the periods nearly 3 to 5 years play a crucial role in the pattern of the rainfall in Ethiopia. The cross-spectrum analysis in general showed that the 3.5 to 5 years periods play crucial role in the influence of ENSO. The result can also be used to forecast the relative intensity of rainfall on the basis of the occurrence of ENSO
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Ethiopian Rainfall Pattern