Observed changes in rainfall amount and extreme events in southeastern Ethiopia, 1955–2015

Abstract

This study analysed spatio-temporal variability and trends in rainfall amount and extreme events in the southeastern part of Ethiopia for the period 1955–2015. Daily rainfall data from 44 recording stations were used to define total rainfall amounts and 12 extreme event indices for three wet seasons and annual time scale. Mann–Kendall’s trend test and Sen’s slope estimator were used to determine trends and rates of change, respectively. Results showed the emergence of different trend signals across seasons and over space in the study area. Trend tests for total rainfall amount and extreme indices for annual and March–May season show a global significant downward tendency. However, the number of wet and dry days, maximum consecutive wet and dry spells and wet day rainfall intensity for the annual time scale show mixed significant upward and downward tendencies, while trends for the number of dry days and maximum consecutive dry spells showed a global significant increasing trend for the March–May season across the study area. On the other hand, mixed global significant upward and downward tendencies were found in all rainfall indices for the June–September season over the northern part of the study area. Different from the two wet seasons, the trend test for the September–November wet season in the southern part of the study area shows an increasing tendency, although only few of the upward trends were statistically significant. In contrast, the number of dry days and maximum dry spell length for this season reveal decreasing trends at most of the stations. Empirical evidences generated in rainfall trends using dense gauging stations provide useful information to develop spatially relevant climate change adaptation and climate risk management plans.