Spatio-temporal analysis of temperature variability, extremes, and trends in Welmel watershed, southeastern Ethiopia

Abstract

This study aims to analyze spatio-temporal temperature variability and extremes in the Welmel watershed, providing a localized assessment using World Meteorological Organization indices to inform climate resilience in agriculture and water systems. To achieve this, historical temperature records from seven meteorological stations were sourced from the Ethiopian Meteorological Institute, providing a robust foundation for comprehensive spatio-temporal analysis. Mann–Kendall’s test and Sen’s slope estimator were used to analyze the trend and magnitude of change, respectively. Spatial interpolation was performed using the Inverse Distance Weighting method. For the temperature extremes analysis, nine indicators recommended by the World Meteorological Organization and the Expert Team on Climate Change Detection and Indices were used. The results showed that significant increasing trends in maximum temperature were observed at Haro (0.087 °C/year) and Rira (0.105 °C/year) annually, with strong seasonal rises, particularly during December-January-February (DJF) and March-April-May (MAM). In contrast, Angetu exhibited a slight decreasing annual trend (-0.009 °C/year), while Madda Walabu showed almost no change (-0.001 °C/year). Similarly, annual minimum temperatures displayed significant warming at Haro (0.133 °C/year) and Rira (0.120 °C/year), with consistent seasonal increases across all periods. Conversely, Bidire and Madda Walabu experienced slight cooling trends, notably during SON at Bidire (-0.025 °C/year), suggesting localized cooling effects. The extreme temperature indices also showed notable changes, with the majority of stations indicating an increasing trend in TXx (annual maximum of daily maximum temperature), TXn (annual minimum of daily maximum temperature), and TNx (annual maximum of daily minimum temperature). The most significant rise was recorded at Rira station, where TXx increased by 0.24 °C per year and TNx by 0.21 °C per year. Angetu and Delo Mena recorded notable warming in TXx and TNx but cooling trends in TXn and TNn. The frequency of summer days (SU) significantly increased at Rira ( 0.54 days/decade) but declined at Angetu (-1.08 days/decade). Warm temperature extremes, particularly warm days (TX90p), became more frequent at Haro and Delo Mena. Overall, the observed warming trends and increasing temperature extremes indicate a shift toward hotter conditions in the Welmel watershed. These changes have critical implications for local agriculture, water resources, and ecosystem stability, highlighting the urgent need for adaptive strategies to enhance climate resilience in Southeastern Ethiopia.