Climate Variability in the Horn of Africa Eastern Countries: Eritrea, Djibouti, Somalia

Abstract

Eritrea, Djibouti and Somalia have peculiar physiographic characteristics and, though their climate is mainly controlled by the north–south–north movement of the Intertropical Convergence Zone (ITCZ), the large difference in elevation (3000 m from sea level to the highest peak) and the variable distance from the ocean also play an important role, accounting for considerable spatial variability in climate characteristics. Gridded and ground instrumental data of mean monthly temperature and precipitation were the main platform to describe the climate of Eritrea, Djibouti and Somalia. The basic precipitation and temperature data were used to obtain other parameters such as rainfall erosivity and aridity indices. Data of other basic parameters such as wind or humidity are available only for a very small number of meteo-stations, and their time series are very short. The gridded data time series span a century-long interval (1901–2015) and were used to investigate mean annual temperature and precipitation trends. A complementary analysis of climate variations was carried out using old (early twentieth century) data reported by Fantoli (Elementi preliminari del clima dell’Etiopia. Sansoni, Firenze, 1940; Contributo alla climatologia della Somalia: riassunto dei risultati e tabelle meteorologiche e pluviometriche. Ministero degli Affari Esteri, Cooperazione Scientifica e Tecnica, Roma, 1965) and modern data. The gridded data time series show a marked increase in temperature in the three countries. A decreasing trend of precipitation is evident for Eritrea, whereas an increasing trend is observed for Somalia. Rainfall erosivity is relatively low, despite the presence of vast degraded areas. The aridity indices indicate that the region is already under desertification conditions and the situation is expected to get worse with a decrease in water resources and severe threats to agricultural productivity.