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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.

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Data availability

We have all the raw, processed data and result products, and if it is required, we can provide the processed data and documents. However, the National Meteorological Agency does not allow us to provide raw precipitation data.

Code availability

The codes used to generate extreme precipitation indices are available, and we can submit if these codes are needed in any circumstances. Similarly, we used the MAKESENS Microsoft Excel add-in software, which is an open source to generate trend magnitude and patterns, and we can make it available if it is needed.

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Acknowledgements

We are very grateful to the Ethiopian National Meteorological Agency (NMA) for providing us with the daily rainfall data used for this study. We also thank the Dire Dawa University for the financial support to the first and second authors.

Funding

This study was funded by the Dire Dawa University. There was no agreement number.

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Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Mekonnen Adnew Degefu and Yonas Tadesse. The first draft of the manuscript was written by Mekonnen Adnew Degefu. Yonas Tadesse and Woldeamlak Bewket reviewed and commented on the first draft of the manuscript. Woldeamlak Bewket has supervised the research work. All authors read and approved the final manuscript.

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Correspondence to Mekonnen Adnew Degefu.

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Degefu, M.A., Tadesse, Y. & Bewket, W. Observed changes in rainfall amount and extreme events in southeastern Ethiopia, 1955–2015. Theor Appl Climatol 144, 967–983 (2021). https://doi.org/10.1007/s00704-021-03573-5

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