Intraseason and seasonal drought trends in Ethiopia were studied using a suite of drought indicators—standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index (PDSI) and Z-index for Meher (long-rainy), Bega (dry), and Belg (short-rainy) seasons—to identify drought-causing mechanisms. Trend analysis indicated shifts in late-season Meher precipitation into Bega in the southwest and southcentral portions of Ethiopia. Droughts during Bega (October–January) are largely temperature controlled. Short-term temperature-controlled hydrologic processes exacerbate rainfall deficits during Belg (February–May) and highlight the importance of temperature- and hydrology-induced soil dryness on production of short-season crops such as tef. Droughts during Meher (June–September) are largely driven by precipitation declines arising from the narrowing of the intertropical convergence zone (ITCZ). Increased dryness during Meher has severe consequences on the production of corn and sorghum. PDSI is an aggressive indicator of seasonal droughts suggesting the low natural resilience to combat the effects of slow-acting, moisture-depleting hydrologic processes. The lack of irrigation systems in the nation limits the ability to combat droughts and improve agricultural resilience. There is an urgent need to monitor soil moisture (a key agro-hydrologic variable) to better quantify the impacts of meteorological droughts on agricultural systems in Ethiopia.

14Ethiopian agriculture is not only affected by precipitation declines (meteorological droughts) but 15 also soil dryness caused by temperature increases and associated long-term hydrological changes. 16Meteorological drought indicators (e.g., SPI), do not fully capture the water deficits in agricultural 17 systems (i.e., agricultural droughts). An Ethiopia-wide assessment of meteorological and 18 agricultural drought trends was carried out to characterize century-scale (1902 -2016) changes in 19droughts. SPI and SPEI calculated using two-month accumulation and the Palmer Z-index were 20 used for assessing intra-season drought trends. SPI and SPEI at six-month accumulations and 21PDSI were used to define full season droughts. Detrended variance corrected Mann-Kendall test 22was used for trend analysis during Bega (dry), Belg (short-rainy) and Meher (long-rainy) seasons. 23The SPEI-2 and PDSI were most aggressive in characterizing intra-season and seasonal-drought 24 trends. There is on average 1% -6% annual increase in dryness with the lower estimate based on 25 precipitation declines and the upper end accounting for seasonal soil moisture dynamics. The area 26 between 37.5 o E -42.5 o E denotes a climate hot-spot. Precipitation declines in Belg along the 27 Ethiopia-South-Sudan/Sudan border during Belg and along Eretria-Ethiopia border during Meher 28have the potential to exacerbate transboundary water conflicts and further threaten the food 29 security of the region. 30 31