Background Rainfall variability exceedingly affects agriculture in Ethiopia, particularly in the eastern region where rainfall is relatively scarce. Hence, understanding the spatiotemporal variability of rainfall is indispensable for planning mitigation measures during high and low rainfall seasons. This study examined the spatiotemporal variability and trends of rainfall in the West Harerge Zone, eastern Ethiopia. Method The coefficient of variation (CV) and standardized anomaly index (SAI) were used to analyze rainfall variability while Mann-Kendall (MK) trend test and Sen’s slop estimator were employed to examine the trend and magnitude of the rainfall changes, respectively. The association between rainfall and Pacific Ocean Sea Surface Temperature (SST) was also evaluated by Pearson correlation coefficient (r). Results The annual rainfall CV during 1983–2019 periods is between 12 and 19.36% while the seasonal rainfall CV extends from 15–28.49%, 24–35.58%, and 38–75.9% for average Kiremt (June–September), Belg (February–May), and Bega (October–January) seasons, respectively (1983–2019). On the monthly basis, the trends of rainfall decreased in all months except in July, October, and November. However, the trends were not statistically significant (α = 0.05), unlike in November. On a seasonal basis, the trends of mean Kiremt and Belg seasons rainfall decreased while it increased in Bega season although it is not statistically significant. Moreover, the annual rainfall showed a non-significant decreasing trend. The findings also revealed that the correlation between rainfall and Pacific Ocean SST was negative for Kiremt while positive for Belg and Bega seasons. Besides, annual rainfall and Pacific Ocean SST was negatively correlated. Conclusions High spatial and temporal rainfall variability was observed at the monthly, seasonal, and annual time scales. Seasonal rainfall has high inter-annual variability in the dry season ( Bega ) than other seasons. The trends in rainfall were decreased in most of the months. Besides, the trend of rainfall decreased in the annual, Belg and Kiremt season while increased in the Bega season. The study also indicated that the occurrence of droughts in the study area was associated with ENSO events like most other parts of Ethiopia and East Africa.

中文翻译：

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埃塞俄比亚东部西哈雷格区降雨时空变化和趋势及其与太平洋海面温度的关系

背景 降雨量的变化极大地影响了埃塞俄比亚的农业，特别是在降雨量相对稀少的东部地区。因此，了解降雨的时空变异性对于规划高雨季和低雨季的缓解措施是必不可少的。本研究考察了埃塞俄比亚东部西哈雷格区降雨的时空变异性和趋势。方法采用变异系数（CV）和标准化异常指数（SAI）分析降雨变率，采用Mann-Kendall（MK）趋势检验和Sen's slop estimator分别检验降雨变化的趋势和幅度。降雨与太平洋海面温度 (SST) 之间的关联也通过皮尔逊相关系数 (r) 进行评估。结果 1983-2019 年期间的年降雨量 CV 介于 12% 和 19.36% 之间，而季节性降雨量 CV 介于 15-28.49%、24-35.58% 和 38-75.9% 之间，平均 Kiremt（6-9 月），比利时（2 月） – 5 月）和 Bega（10 月至 1 月）季节，分别为（1983-2019 年）。分月看，除7月、10月和11月外，其他月份降雨量均呈下降趋势。然而，与 11 月不同，这些趋势在统计上并不显着（α = 0.05）。在季节性基础上，Kiremt 和Belg 季平均降雨量呈下降趋势，而Bega 季则呈上升趋势，但无统计学意义。此外，年降水量呈不显着下降趋势。研究结果还表明，降雨量与太平洋海温之间的相关性对于基雷姆特来说是负相关，而在贝尔格和贝加季节是正相关。此外，年降雨量与太平洋海温呈负相关。结论 在月、季和年时间尺度上观察到高时空降雨变异性。与其他季节相比，旱季 (Bega) 的季节性降雨量年际变化较大。大部分月份降雨量呈下降趋势。此外，年降水量、贝尔格季和基里姆特季降水量呈下降趋势，贝加季降水量呈上升趋势。该研究还表明，与埃塞俄比亚和东非的大多数其他地区一样，研究区干旱的发生与 ENSO 事件有关。结论 在月、季和年时间尺度上观察到高时空降雨变异性。与其他季节相比，旱季 (Bega) 的季节性降雨量年际变化较大。大部分月份降雨量呈下降趋势。此外，年降水量、贝尔格季和基里姆特季降水量呈下降趋势，贝加季降水量呈上升趋势。该研究还表明，与埃塞俄比亚和东非的大多数其他地区一样，研究区干旱的发生与 ENSO 事件有关。结论 在月、季和年时间尺度上观察到高时空降雨变异性。与其他季节相比，旱季 (Bega) 的季节性降雨量年际变化较大。大部分月份降雨量呈下降趋势。此外，年降水量、贝尔格季和基里姆特季降水量呈下降趋势，贝加季降水量呈上升趋势。该研究还表明，与埃塞俄比亚和东非的大多数其他地区一样，研究区干旱的发生与 ENSO 事件有关。年、Belg 和Kiremt 季降雨量呈减少趋势，而Bega 季则呈增加趋势。该研究还表明，与埃塞俄比亚和东非的大多数其他地区一样，研究区干旱的发生与 ENSO 事件有关。年、Belg 和Kiremt 季降雨量呈减少趋势，而Bega 季则呈增加趋势。该研究还表明，与埃塞俄比亚和东非的大多数其他地区一样，研究区干旱的发生与 ENSO 事件有关。