Spatiotemporal variability and trend of rainfall and temperature in Sidama Regional State, Ethiopia

Abstract

This study aims to investigate spatiotemporal variability, trends, and anomaly in rainfall and temperature in the Sidama region, Ethiopia. The TerraClimate gridded dataset on a monthly time scale for 30 years (1991–2020) with a horizontal resolution of approximately 4 km was used for the study. Trends in annual and seasonal rainfall and temperature were assessed using a nonparametric test (Mann-Kendal test) and Sen’s slope to test the statistical significance and magnitude of trends (increase/decrease), respectively. Our findings revealed that annual rainfall, summer (Hawado), and spring (Badhessa) rainfall have shown an increasing trend in most parts of the region, except for its northwest parts. We found a low annual rainfall variability (CV < 13%) over the southeastern and northwestern parts of the region. Rainfall variability revealed the difference in both time and space across the region. Six drought years (1999, 2001, 2002, 2003, 2012, and 2019) with different magnitudes were identified across the region. Annual average maximum (up to 0.4 °C decade−1) and minimum (up to 0.25 °C decade−1) temperatures revealed significantly increasing trends across the region. The standardized anomaly in the mean annual temperature indicated that the years in the recent decade (2011–2020) are getting warmer compared to the past two decades (1991–2010) due to natural and anthropogenic activities causing weather extremes in the region. The results of this study for rainfall contradict the other studies in the rift valley part of the region. Therefore, we suggest appropriate climate change adaptation strategies so that there is high rainfall and temperature variability across the region and between seasons.

Analysis of rainfall and temperature variabilities in Sidama regional state, Ethiopia

“…On the other hand, Wonsho and Hawassa Zuriya are situated in the Midland (1800–3200 masl) and lowland (1500–1800 masl) agri-environmental regions [ 35 ]. The study districts experience two distinct rainy seasons [ 28 , 31 , 36 ]. The primary rainy season, known as Kiremt, occurs from June to mid-September, while the shorter rainy season, called Belg, takes place between March and May [ 31 ].…”

“…The study districts experience two distinct rainy seasons [ 28 , 31 , 36 ]. The primary rainy season, known as Kiremt, occurs from June to mid-September, while the shorter rainy season, called Belg, takes place between March and May [ 31 ]. The Belg season's irregularity poses challenges for crop production and harvesting [ 19 ].…”

“…The Belg season's irregularity poses challenges for crop production and harvesting [ 19 ]. Due to the delayed onset, early termination, and poor performance of the Belg rainy season, the study districts currently facing food shortages [ 16 , 31 , 34 ].

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“…There is no consensus among previous studies carried out in the country on how precipitation and temperature change over different regions and periods. Some of them report an increase in rainfall, while others show a decrease [ 6 , 11 , 25 , [29] , [30] , [31] ]. For instance Ref.…”

“…In contrast, Matewos and Tefera [ 19 ] discovered notable and statistically significant declines in short-rainy season rainfall particularly in the northeastern Sidama region . More recently Ware et al [ 31 ] reported a steady drop in the average yearly precipitation, along with a notable reduction in both the short and long rainy seasons in Sidama region. Furthermore, Matewos and Tefera [ 19 ] also documented significant variability for the onset and cessation of rainfall , spatially and temporally.…”