Drought assessment and rainfall trend analysis in southwestern Nigeria

Prolonged instability and insufficiency of rainfall resulting in drought, extreme weather events, and food insecurity are climate change‐related challenges bedeviling humanity. This study assessed drought conditions and rainfall trends in southwestern Nigeria, using the 1984–2014 rainfall dataset from the Nigerian Meteorological Agency (NIMET). The coefficient of variation (CV), long‐term standardized precipitation index (SPI), serial correlation test, Mann–Kendall trend analysis, Sens's slope estimation, and Pettit test were carried out using various R programming packages. Long‐term mean annual rainfall ranged between 1224.7 and 1537.1 mm. The highest variation (17.3%) was observed for Abeokuta and Ikeja. SPI analysis revealed Ibadan and Oshogbo as the driest and wettest stations, respectively. There was no serial autocorrelation in the dataset. The Mann–Kendall trend showed an upward rainfall trend for Abeokuta, Ibadan, and Ikeja and a downward trend for Akure and Oshogbo. Sen's slope annual rates of change in mm for Abeokuta, Akure, Ibadan, Ikeja, and Oshogbo are 6.69, −2.36, 2.07, 7.82, and 1.42 respectively. The Pettit test revealed change points that are not statistically significant. The drought assessment largely showed a cyclical SPI pattern with greater years of dryness. Given the increasing impact of climate change, future studies are needed to simulate the local drivers of drought severity and frequency and the changing rainfall pattern in rapidly urbanizing cities. There is also the need to incorporate climate‐related adaptive strategies in existing water management policies. 长期的降雨不稳定性和不足导致干旱、极端天气事件和粮食不安全, 这为人类不断带来与气候变化相关的挑战。本研究使用尼日利亚气象局 (NIMET)提供的1984–2014年降雨数据集, 评估了尼日利亚西南部的干旱状况和降雨趋势。使用不同的R语言包计算变异系数 (CV)、长期标准化降水指数 (SPI)、序列相关检验、Mann‐Kendall趋势分析、Sen斜率估计和Pettit检验。长期平均年降雨量介于 1224.7–1537.1 毫米之间。阿贝奥库塔和伊凯贾的降水差异最大(17.3%)。SPI 分析表明, 伊巴丹的站点最干燥、奥绍博的站点最潮湿。数据集不存在序列自相关。Mann‐Kendall 趋势显示, 阿贝奥库塔、伊巴丹和伊凯贾的降雨量呈上升趋势, 而阿库雷和奥绍博的降雨量呈下降趋势。 阿贝奥库塔、阿库雷、伊巴丹、伊凯贾和奥绍博的 Sen 斜率年变化率 (以毫米计)分别为 6.69、‐2.36、2.07、7.82和1.42。Pettit检验揭示了在统计学上不显著的变化点。干旱评估在很大程度上显示了周期性的SPI模式, 其中包括更严重的干旱年份。鉴于气候变化的影响越来越大, 未来研究需要模拟干旱严重程度和频率的地方驱动因素, 以及快速城市化地区不断变化的降雨模式。还需要将与气候相关的适应性战略整合到现有的水资源管理政策。. La inestabilidad prolongada y la insuficiencia de precipitaciones que provocan sequías, fenómenos meteorológicos extremos e inseguridad alimentaria son desafíos relacionados con el cambio climático que acosan a la humanidad. Este estudio evaluó las condiciones de sequía y las tendencias de las precipitaciones en