Climatological Study of SPEI Drought Index Using Observed and CRU Gridded Dataset over Ethiopia

Abstract This study aims to investigate the standardized precipitation evapotranspiration index (SPEI) using monthly observed and gridded Climate Research Unit (CRU) dataset across 13 stations in Ethiopia during period 1970–2005. SPEI is computed at a 4-month timescale represent drought Belg (February–May) Kirmet (June–September) seasons separately, an 8-month these two together (February–September). The results show that there are extremely strong correlations ( R ≥ 0.8) between estimated values from CRU values, with root mean square error (RMSE) of 4–99 mm percentage (MPE%) −30 73% most stations. For temperature SPEI, shows almost (0.6 ≤ < 0.8), while dominant RMSE MPE 0.7–5 °C −22 26%, respectively, for 0.28–0.96 −49 55%, three seasons. It also found each clusters (dry, normal, wet) has high success (≥ 60%) more than 50% stations, general accuracy exceeds 60% 75% Finally, correct hits often within corresponding cluster but may shift into another category (extreme, severe, moderate) except few events.