Spatial Analysis of Climate variability and Change in the Great Ethiopian Rift Valley Basins

Abstract

The generally high temporal and spatial climate variability and change in most parts of Ethiopia, where rainfed farming is the main form of crop production, has been the main cause of food insecurity in significant areas of the country. Spatial variations in selected climate variables were investigated for the great Rift Valley regions of Ethiopia during the baseline (1981-2010) and projected (2021-2100) periods. Baseline climate data from 16 stations that represent different agroecology were obtained from National Meteorology Agency of Ethiopia (NMA) (http://www.ethiomet.gov.et). Corresponding projected data grided over 0.5ᵒ X 0.5ᵒ were retrieved from eight GCM-RCM combinations under two Representative concentration pathways (RCPs) from CORDEX database (http://www.cordex.org).  First order Markov chain model was used for missing rainfall data filling. Coefficient of variation and standardized anomaly index descriptors were used in the analysis of climate data for each station. Spatial maps were then generated from station values using the ordinary kriging method of interpolation. The result indicated that rainfall of the study basins showed both spatial and temporal variabilities. The total annual rainfall showed variation in the year-to-year variability ranging from low in the southern half to high in the northern half of the basins. Seasonal rainfall showed high to very high variability which is challenging to rainfed agriculture. For the projected periods, majority of the climate models projected a decline in annual rainfall and increase in temperature. HadGEM2-ES_RCA4 model simulation suggested precipitation change varying from +4.2 to -16% and +3.8 to -18% for near period under RCP4.5 and RCP8.5 emission scenarios, respectively. Mean temperature is projected to rise from +0.7 to +1.25 ºC under RCP4.5 to +0.9 to +1.6 ºC under RCP8.5 across the GRVB in the near future and further warming was projected in the mid and end centuries. Rainfed crop production in the region, which is already impacted by the current climate variability, is likely to be further challenged with future climate change. As a consequence, specific impact -based adaptation strategies are essential to reduce the vulnerability of rainfed crop production in the area.

Keywords: Climate models, growing season, Rift Valley, seasonal water deficit, dry spell

DOI: 10.7176/JEES/11-16-01

Publication date:June 30^th 2021