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INTRODUCTION
Climate variability and change cause a wide range of adverse impacts, particularly in developing countries. Eastern Africa faced serious challenges recently because of frequent drought and excessive rainfall events (Viste et al. 2013; Gebrechorkos et al. 2019). Unpredictable rainfall amount and distribution behavior has become a bottleneck for agricultural and livestock production (Intergovernmental Panel on Climate Change (IPCC) 2007, 2014). Detailed analysis and quantifying the spatial distribution of rainfall are required in water resource management, climate change studies and similar applications (Yadav et al. 2014).
Rainfall varies significantly in Ethiopia at both temporal and spatial scales. Most of the areas (more than 70%) in the country receive rainfall during the Kiremt season which extends from mid-June to mid-September (Korecha & Barnston 2007). Spatially, the country is known for diverse topography including mountains, dissected plateaus, valleys and plainlands or lowlands that affects rainfall distribution (Degefu et al. 2017). Areas with an average elevation of below 1500 m are known for the warm (hot) and semi-arid (arid) type of climate where rainfall is seriously scarce. These arid and semi-arid lands are located at the peripheries and most people inhabiting the region are either pastoralist (purely dependent on livestock systems) or agropastoral (dependent on both livestock raising and subsistence crop farming), constituting 10–12% of the total population. Climate change has far-reaching repercussions for Ethiopia due to its rain-dependent agricultural systems and the vast area of the country covered by arid and semi-arid lands (National Meteorological Agency [NMA] of Ethiopia 2018).
The variability and trend analysis of precipitation has obtained due attention and many researchers have shown interest in this area due to its tremendous impact on both socio-economic and environmental challenges. Several studies on rainfall variability and trend have been conducted in Ethiopia. Most of these papers emphasized highland areas (central, northwestern, northeastern and southwestern) (Rosell 2011; Ayalew et al. 2012; Kheireldin et al. 2016; Arragaw & Woldeamlak 2017; Fitsum et al. 2017; Birara et al. 2018; Alemu & Bawoke 2020; Etana et al. 2020; Geremew et al. 2020; Mekonnen & Berlie 2020; Shawul & Chakma 2020; Feke et al. 2021) and a few papers were conducted in a lowland area (Urgessa 2013; Degefu & Bewket 2014; Ahmed et al. 2017; Befikadu et al. 2018). On...