Historical Trend Analysis and Future Projections of Rainfall in Amhara, Ethiopia

Abstract

Understanding rainfall trends & projections is essential for water resource management. This study showed historical (1981-2020) and future (2021-2100) rainfall amounts and trends across 71 grid points separated by 0.44o in Amhara and Amhara’s five rainfall regimes (A3, A4, A5U, A5L, A6). Ground and satellite merged historical data from Ethiopia Meteorology Institute (EMI) and the Rossby Centre Regional Atmospheric Model (RCA) forced by an ensemble of the best-performed Global Circulation Models (GCMs) in Amhara, HadGEM2-ES of UK and MPI-ESM-LR of Germany, in three Representative Concentration Pathway (RCP) scenarios, RCP2.6, RCP4.5, and RCP8.5 from CORDEX project were the basis of dataset. Amhara’s annual, seasonal, and monthly historical rainfall trends mostly increased. During Jun-Sep (Kiremt), lower rainfall receiving regimes (A6, A5L, A5U) had a significant increasing trend (~ 4 mm/year), while wetter regimes (A3 & A4) had a non-significant increasing (< 1 mm/year) and decreasing (~ -0.5 mm/year) trends, respectively. Generally, compared to the climatology, the annual and Kiremt rainfall in Amhara is projected to increase in the near-term (2021-2040) and mid-term (2041-2060) and decrease in the long-term (2081-2100); Oct-Jan (Bega) rainfall is projected to increase in all future terms and all RCP scenarios while Feb-May (Belg) rainfall will be abrupt