Trend and periodicity of drought over Ethiopia

Zeleke, Tadesse Terefe; Giorgi, Filippo; Diro, G. T.; Zaitchik, B. F.

doi:10.1002/joc.5122

Cited by 85 publications

(62 citation statements)

References 55 publications

(190 reference statements)

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“…A study by Viste et al [34] reported that even through the degree of drying varies spatially, all the studied areas experienced drought at annual scales in Ethiopia. Zeleke et al [35] documented that south and southwestern regions of Ethiopia have experienced drying, while the central mountainous, north, and northwestern regions had no observed long-term trends. Recently, Worku et al [36] reported a warming trend in extreme temperature indices while an increase in rainfall extreme events in Jemma Subbasin, Upper Blue Nile Basin.…”

Section: Introductionmentioning

confidence: 99%

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

Esayas

Simane

Teferi

et al. 2018

Advances in Meteorology

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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.

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Section: Introductionmentioning

confidence: 99%

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

Esayas

Simane

Teferi

et al. 2018

Advances in Meteorology

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“…Drought-event is defined as a condition on land described by deficiency of water that falls below threshold level or normal average values for a certain period of time [18], [23], [24]. The deficiency of water has significant impact on surface and ground water resources [19].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Drought and Wet-Events Using SWSI-Based Severity-Duration-Frequency (SDF) Curves for the Upper Tana River Basin, Kenya

Wambua¹

2018

HYD

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Drought and wet-event patterns in the Upper Tana River basin have significantly been changing due to variation of climatic and human-induced factors. This paper presents the analysis of drought and wet-events using Severity-Duration-Frequency (SDF) curves for the Upper Tana River basin, Kenya based on Surface Water Supply Index (SWSI). The extreme value EV1 (Gumbel) frequency distribution function was used to formulate SDF curves. The developed SDF curves were used to develop isoseverity maps for the basin. From the results, the event-probability show that likelihood of drought events increased linearly with increase in magnitude of SWSI while the return period of drought events increased exponentially with decrease in magnitude of SWSI. The findings show that the probability and magnitude, the return period and magnitude of drought have linear and exponential regression coefficients of 0.984 and 0.980 respectively. On the other hand the probability of wet-period events decreased linearly with increase in magnitude of SWSI while the return period of the events increased exponentially with increase in magnitude of SWSI with regression coefficients of the linear and exponential functions of 0.804 and 0.881 respectively. This indicates that both the drought and wet-events probability and magnitude, and the return period and magnitude have a strong correlation. Spatially, it was found that generally the river basin exhibit an increasing pattern in cumulative SWSI in south-eastern areas than the north-eastern and generally a more increase in extreme wet-events than droughts in the basin. The developed (SDF) curves are critical for design of hydrologic, hydraulic and water resources supply systems while the spatial event-patterns can be incorporated in prioritized mitigation of extreme events.

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“…Its reliability is also likely to be higher in warm climates (such as Ethiopia), where the hydrology is not affected by spring snowmelt. PDSI has also been used widely to characterize agricultural droughts [13,52,53]. Studies have shown that PDSI correlates strongly with SPI values computed using higher accumulations [54,55].…”

Section: Selection Of Meteorological and Agricultural Drought Indicatorsmentioning

confidence: 99%

Comparison of Meteorological- and Agriculture-Related Drought Indicators across Ethiopia

Tsige

Uddameri

Forghanparast

et al. 2019

Water

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Meteorological drought indicators are commonly used for agricultural drought contingency planning in Ethiopia. Agricultural droughts arise due to soil moisture deficits. While these deficits may be caused by meteorological droughts, the timing and duration of agricultural droughts need not coincide with the onset of meteorological droughts due to soil moisture buffering. Similarly, agricultural droughts can persist, even after the cessation of meteorological droughts, due to delayed hydrologic processes. Understanding the relationship between meteorological and agricultural droughts is therefore crucial. An evaluation framework was developed to compare meteorologicaland agriculture-related drought indicators using a suite of exploratory and confirmatory tools. Receiver operator characteristics (ROC) was used to understand the covariation of meteorological and agricultural droughts. Comparisons were carried out between SPI-2, SPEI-2, and Palmer Z-index to assess intraseasonal droughts, and between SPI-6, SPEI-6, and PDSI for full-season evaluations. SPI was seen to correlate well with selected agriculture-related drought indicators, but did not explain all the variability noted in them. The correlation between meteorological and agricultural droughts exhibited spatial variability which varied across indicators. SPI is better suited to predict non-agricultural drought states than agricultural drought states. Differences between agricultural and meteorological droughts must be accounted for in order to devise better drought-preparedness planning.

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Trend and periodicity of drought over Ethiopia

Cited by 85 publications

References 55 publications

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

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

Analysis of Drought and Wet-Events Using SWSI-Based Severity-Duration-Frequency (SDF) Curves for the Upper Tana River Basin, Kenya

Comparison of Meteorological- and Agriculture-Related Drought Indicators across Ethiopia

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