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

Abstract

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 southwestern 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 southeastern parts of Ethiopia extending to the southwest covering Somali and Oromia regions. Similar trends are also observed in the greatest 3-, 5-and 10day 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.

Evaluation and Application of Multi-Source Satellite Rainfall Product CHIRPS to Assess Spatio-Temporal Rainfall Variability on Data-Sparse Western Margins of Ethiopian Highlands

“…This pattern of variability of rainfall has been reported from nearby regions [43,60]. Since 1980, Ethiopia at country level experienced severe drought events in 1983-1985, 1988, 2000, 2002-2003, 2006, 2011 and 2015 [64]. Similarly, our study area also experienced most of these drought events (Figure 8) except years 1988, 2000, 2006 and 2015.…”

“…National and watershed level analysis of rainfall in Ethiopia using gauge data shows most parts of the country shows statistically insignificant trends in rainfall [43,63,64]; however, our analysis of trends at a basin level using CHIRPS rainfall data demonstrated some significant trends of rainfall that vary locally. A significant increasing trend of rainfall was identified in the driest lower part of Beles Basin (Figure 11).…”

“…Previous studies in the region [52,55,63] have reported inverse relationship between CV and annual rainfall. The rainfall in the Beles Basin is characterized by moderate temporal interannual variability (Figure 11a) as compared to country level interannual variability with a high CV reaching up to 30% [64]. The low rainfall areas of the basin show high interannual variability, implying that in these regions there is a greater contrast in annual rainfall from year to year.…”

“…Extremely dry years in the country significantly affected the agricultural sector. Understanding the pattern of rainfall variability is essential because negative rainfall trends mostly result in a higher probability of droughts that have historically affected millions of people in Ethiopia [56,63,64]. It has been reported that the interannual variability of rainfall in the region could be under the influence of El Niño-Southern Oscillation (ENSO), and the Indian Ocean Sea Surface Temperature (SST) [43,52,65,66].…”

Spatial distribution and trends of different precipitation variability indices based on daily data in Northern Chile between 1966 and 2015

“…From a climatic point of view, it is well known that monthly amounts provide valuable information regarding the precipitation of a given territory. Traditionally, the focus has been placed on means and the extreme rainfall of concrete regions around the world at global (Berghuijs et al, ) and regional scales: the Mediterranean (Caloiero et al, ; Lazoglou et al, ; Zittis, ), the rest of Europe (Panagos et al, ; Beranová and Kyselý, ; Brown, ), Africa (Abahous et al, ; Gummadi et al, ), Asia (Jiang et al, ; Kim et al, ; Ullah et al, ; Zhao et al, ), and America (Bernardino et al, ; Ciemer et al, ; Valdés‐Pineda et al, ).…”