Assessing the Trends and Variabilities of Seasonal and Annual Rainfall Across South Ethiopia

Understanding rainfall variability and trends of historical rainfall data is crucial for decision-makers to take appropriate steps and interventions to avert the hazards posed by rainfall variations and variability, particularly extremes, in order to improve community adaptation and mitigation efforts in southern Ethiopia. The monthly rainfall data are obtained from FEWSNET website, of the years 1981–2022, are for six locations of 4x4 km grids. One grid point was selected from each of the seven homogenous rainfall zones using merged weather stations data and meteorological satellite measurements. Annual long term mean rainfall varies from 331.8 to 1324.3 mm/year across the region. The temporal variability and trends of annual and seasonal rainfall data at six homogenous rainfall zones in South Ethiopia are examined in this study. The results indicates high rainfall variability across most zones especially in the year 1997 was the wettest year while 1984 was the driest year. This study employed the Mann-Kendall test and Sen's slope estimator to analyze yearly and seasonal rainfall trends. The results indicate that the annual and Belg rainfall exhibit statistically insignificant decreasing trends in most of the zones however, Bega seasonal rainfall shows significant increasing trends. The study's findings can assist decision-makers in taking appropriate steps and interventions to deter the risks posed by rainfall variations and unpredictability, particularly extremes, in order to boost community adaptation and mitigation efforts in southern Ethiopia.