Effects of sea surface temperatures on monthly and dekadal Kiremt rainfall variability in the contrasting topographical regions of northern Ethiopia

Studies on rainfall variability to Sea Surface Temperature (SST) effects in arid and semi-arid parts of northern Ethiopia have been limited. This paper investigates the SST drivers of rainfall variability in contrasting areas of northern Ethiopia during the main rainy season "Kiremt" on monthly and dekadal (Ten-days) time scales. We analyzed daily rainfall records (1988-2017) from 41 meteorological stations across four homogeneous rainfall zones in northern Ethiopia's highlands and lowlands. Correlation analysis and multiple linear regression models were employed to examine the relationships between global SST and Kiremt rainfall, with the aim of predicting monthly and dekadal rainfall. Results reveal distinct rainfall distributions: the lowland receives bi-modal pattern with rainfall amount < 80 mm during the main rain season, while the highlands exhibit uni-modal pattern with rainfall amount of 350 mm. The variability in Monthly and dekadal rainfall in the lowlands and highlands is mainly linked to SST in the equatorial Pacific Ocean. Changes in SST in the Atlantic and Indian Oceans also significantly impact monthly and dekadal rainfall variability, regardless of their strength and lag-time effect. Warming of the western equatorial Pacific and Indian Ocean, and tropical northeast Atlantic Ocean enhances the rainfall over the highlands and lowlands while the eastern and central equatorial Pacific causes the declining of the rainfall. The prediction models for monthly and dekadal rainfall archived a moderate to good performance, with R(2 )ranging from 28%-61%. Efficient methods for predicting Kiremt rainfall are profoundly important to support systematic and informed decision-making in agriculture and water resource sectors.