Spatial and Temporal Characteristics of Wet and Dry Spells During the Kiremt Season Over Ethiopia

The understanding of changes of rainfall patterns and climate extremes are crucial factors for addressing agricultural risks and sustaining water resources in Ethiopia. This study aims to investigate baseline rainfall climatology (1991-2020) and long-term spatiotemporal changes (1981-2022) of Kiremt seasonal rainfall totals (PRCPTOT) and selected ETCCDI-based rainfall indices across Ethiopia. The daily rainfall was analyzed using the Mann-Kendall test and Sen’s slope estimator to examine changes of wet and dry spell frequencies (NWS and NDS), spell durations (MWSL and MDSL) and total wet and dry days (TWD and TDD) from gridded and gauge-based datasets. The baseline climatology reveals a clear rainfall gradient with seasonal totals over 800 mm and more than 80 wet days in western highlands, while less than 400 mm and maximum dry spells over 80 days observed in the eastern lowlands. Kiremt rainfall significantly increased at a national scale by 2.56 mm/year (p = 0.004), specifically the central, western and northern highlands. However, the wet- and dry-spell frequencies increased while the maximum wet-spell duration showed no consistent trend while the total wet days declined recently. These changes suggest greater intra-seasonal rainfall variability with concentrated rainfall and frequent dry spells influencing risks of soil erosion, runoff, and water stress and crop yields. Therefore, it requires soil-moisture conservation, rainwater harvesting and climate-smart agricultural practices.