Trends in climate extremes at local farming calendar timescale: evidence from Merti District, Ethiopia
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ORIGINAL ARTICLE
Trends in climate extremes at local farming calendar timescale: evidence from Merti District, Ethiopia B. Wubishaw Endale1 · E. Mini Simphiwe2 · A. Abegaz Yimer3 Received: 8 May 2020 / Accepted: 19 September 2020 © Springer Nature Switzerland AG 2020
Abstract This study analysed trends in extreme rainfall and temperature indices at three local farming calendar time (LFCT) periods, namely land preparation period (LPP), sowing and maintenance period (SaMP) and harvesting and threshing period (HaTP). The study was carried out over three agro-climatic zones (ACZs) (Kolla, Woina-Dega and Dega) of Merti district, Ethiopia. The three LFCT periods for the main Meher season in each ACZ were defined through focus group discussions (FGDs). Eight and five indices were defined from daily rainfall and temperature data series, respectively, for three stations for the period 1985–2014. INSTAT+ software and Microsoft Office EXCEL were employed to compute the indices. Mann Kendall’s and Sen’s methods were used to determine statistical significance and magnitude of the changes in the indices, respectively. Unlike Dega ACZ, most extreme rainfall indices in Kolla and Woina-Dega have shown decreasing tendency during LPP, while increasing tendency during HaTP. More complex trend results in extreme rainfall indices have been observed during SaMP than during LPP and HaTP. However, the trend tests revealed upward trends for most of the extreme temperature indices. Although the observed trends were not statistically significant for most of the extreme rainfall indices, the upward and downward signals could have negative implications for Meher crop production in Merti district. Because rainfall extreme indices in different ACZs tend to reflect LFCT-specific trends, adaptation interventions in Meher crop production in the study area tend to be based on LFCT- and ACZ-specific climate evidence. Keywords Extreme rainfall indices · Extreme temperature indices · Agro-climatic zone · Trends · Local farming calendar time · Ethiopia
Introduction The demand for information on local climate extremes has significantly increased in current time due to increasing impacts on the natural and human systems including agricultural activities. Evidences generated from empirical
* B. Wubishaw Endale [email protected] E. Mini Simphiwe [email protected] A. Abegaz Yimer [email protected] 1
University of South Africa, Pretoria, South Africa
2
Department of Geography, University of South Africa, Pretoria, South Africa
3
Department of Geography and Environmental Studies, Addis Ababa University, Addis Ababa, Ethiopia
observation (Mika 2013) and model studies (Hanson et al. 2007; Moriondo et al. 2011; Orlowsky and Seneviratne 2012; Omondi et al. 2014; Yu et al. 2018) confirm that frequency, intensity, timing and geographical extent of extreme climate phenomena (e.g. droughts and floods) have been changing mainly due to anthropogenic induced climate change (Intergovernmental Panel on Climate Change (IPCC) 2007). Similar
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