Spatio-temporal variability and trends of precipitation and extreme rainfall events in Ethiopia in 1980–2010

• Published in: Theoretical and applied climatology Vol. 134; no. 3-4; pp. 1315 - 1328
• Main Authors: Gummadi, Sridhar, Rao, K. P. C., Seid, Jemal, Legesse, Gizachew, Kadiyala, M. D. M., Takele, Robel, Amede, Tilahun, Whitbread, Anthony
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.11.2018; Springer; Springer Nature B.V
• Subjects: Agriculture; Analysis; Annual rainfall; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climate; Climate change; Climate science; Climatic data; Climatology; Coefficient of variation; Earth and Environmental Science; Earth Sciences; Ethiopia; Extreme weather; Indonesia; meteorological data; Original Paper; Precipitation; Precipitation variability; Rain; Rainfall; Rainfall variability; Regions; Seasonal rainfall; Seasons; Temporal variability; temporal variation; Temporal variations; Trends; Waste Water Technology; Water Management; Water Pollution Control; Wet days; Ethiopia; Indonesia
• DOI: 10.1007/s00704-017-2340-1
• ISSN: 0177-798X

This article summarizes the results from an analysis conducted to investigate the spatio-temporal variability and trends in the rainfall over Ethiopia over a period of 31 years from 1980 to 2010. The data is mostly observed station data supplemented by bias-corrected AgMERRA climate data. Changes in annual and Belg (March–May) and Kiremt (June to September) season rainfalls and rainy days have been analysed over the entire Ethiopia. Rainfall is characterized by high temporal variability with coefficient of variation (CV, %) varying from 9 to 30% in the annual, 9 to 69% during the Kiremt season and 15–55% during the Belg season rainfall amounts. Rainfall variability increased disproportionately as the amount of rainfall declined from 700 to 100 mm or less. No significant trend was observed in the annual rainfall amounts over the country, but increasing and decreasing trends were observed in the seasonal rainfall amounts in some areas. A declining trend is also observed in the number of rainy days especially in Oromia, Benishangul-Gumuz and Gambella regions. Trends in seasonal rainfall indicated a general decline in the Belg season and an increase in the Kiremt season rainfall amounts. The increase in rainfall during the main Kiremt season along with the decrease in the number of rainy days leads to an increase in extreme rainfall events over Ethiopia. The trends in the 95th-percentile rainfall events illustrate that the annual extreme rainfall events are increasing over the eastern and south-western parts of Ethiopia covering Oromia and Benishangul-Gumuz regions. During the Belg season, extreme rainfall events are mostly observed over central Ethiopia extending towards the southern part of the country while during the Kiremt season, they are observed over parts of Oromia, (covering Borena, Guji, Bali, west Harerge and east Harerge), Somali, Gambella, southern Tigray and Afar regions. Changes in the intensity of extreme rainfall events are mostly observed over south-eastern parts of Ethiopia extending to the south-west covering Somali and Oromia regions. Similar trends are also observed in the greatest 3-, 5- and 10-day rainfall amounts. Changes in the consecutive dry and wet days showed that consecutive wet days during Belg and Kiremt seasons decreased significantly in many areas in Ethiopia while consecutive dry days increased. The consistency in the trends over large spatial areas confirms the robustness of the trends and serves as a basis for understanding the projected changes in the climate. These results were discussed in relation to their significance to agriculture.