Trends in Extreme Climate Events over Three Agroecological Zones of Southern Ethiopia

Abstract

The study aims to assess trends in extremes of surface temperature and precipitation through the application of the World Meteorological Organization’s (WMO) Expert Team on Climate Change Detection and Indices (ETCCDI) on datasets representing three agroecological zones in Southern Ethiopia. The indices are applied to daily temperature and precipitation data. Nonparametric Sen’s slope estimator and Mann–Kendall’s trend tests are used to detect the magnitude and statistical significance of changes in extreme climate, respectively. All agroecological zones (AEZs) have experienced both positive and negative trends of change in temperature extremes. Over three decades, warmest days, warmest nights, and coldest nights have shown significantly increasing trends except in the midland AEZ where warmest days decreased by 0.017°C/year (p<0.05). Temperature extreme’s magnitude of change is higher in the highland AEZ and lower in the midland AEZ. The trend in the daily temperature range shows statistically significant decrease across AEZs (p<0.05). A decreasing trend in the cold spell duration indicator was observed in all AEZs, and the magnitude of change is 0.667 days/year in lowland (p<0.001), 2.259 days/year in midland, and 1 day/year in highland (p<0.05). On the contrary, the number of very wet days revealed a positive trend both in the midland and highland AEZs (p<0.05). Overall, it is observed that warm extremes are increasing while cold extremes are decreasing, suggesting considerable changes in the AEZs.

Climate Variability and Farmers’ Perception in Southern Ethiopia

“…ough not statistically significant, a decreasing trend was observed (1.80 mm/year and 0.11 mm/year) in the lowland and highland AEZ, respectively, while an increasing trend (10 mm/year) (p < 0.05) was exhibited in the midland AEZ. e increasing trend in the ATR in the midland AEZ was in line with findings of other researchers [28,30], in which the midland AEZ experienced an increasing trend in the ATR. Likewise, Weldegerima et al [21] reported an increase in ATR in three stations in Northern Ethiopia.…”

“…In addition, over 60% of farmers in the highland AEZ perceived an increase in rainy season temperature while a comparable proportion of farm households perceived increased temperature in the rainy season both in the midland and lowland AEZs ( Figure 7). e farmers' perception results are in line with a recent study in the same AEZs [30]. Others studies observed similar patterns in different parts of Ethiopia [25,26,32,38,39,76].…”

“…In support of this, Ethiopian Panel on Climate Change (EPCC) [83] has recognized highland areas among the most vulnerable agroecology in Ethiopia. Esayas et al [30] also reported that the highland AEZ in Wolaita experienced a rapid rate of change in the extreme climate events compared to the lowland AEZ over three decades. Deressa et al [31] further noted that farmers from the highland AEZ in the Nile basin perceived climate change more than those in the lowland AEZ.…”

“…Other studies show positive trends in air temperature and negative trends in rainfall [24][25][26][27]. Other studies [28][29][30] observed both increasing and decreasing trends in the climate parameters, including extreme climate in the study area. However, none of the previous studies have linked their climate trend analysis with farmers' perceptions and its influencing factors.…”

“…Size and Procedure. Following Esayas et al [30], this study is based on a gridded daily (4 km by 4 km spatial resolution) temperature and rainfall data running from 1983 to 2014. e data are a combination of two data sets. First, station data were used sourced from the National Meteorological Agency (NMA) of Ethiopia.…”