ABSTRACT The impact of climate change is often demonstrated by rainfall and its attributes. Consequently, this study analyzes rainfall concentration, temporal trends, and rates of change in the savannah zones of Nigeria. Rainfall data were acquired from the archives of the Environmental Management Programme, Federal University of Technology, Minna, for 13 synoptic stations at annual, seasonal, and monthly time scales for the 1970–2016 period. The precipitation concentration index (PCI), Mann–Kendall trend test, Theil–Sen’s slope estimator (β), and relative percentage change methods were adopted for data analysis. The findings reveal that PCI calculated on an annual scale falls into three categories 11–15, 16–20, and PCI > 20. Two distinct patterns emerged from the calculated PCI indicating that stations in the Guinea savannah zone (Bida, Yola, Minna, Jos, Bauchi, and Kaduna) have moderate, irregular, and strongly irregular rainfall concentrations, whereas stations in the Sudano-Sahelian savannah zone (Kano, Gusau, Maiduguri, Yelwa, Nguru, Sokoto, and Katsina) have irregular and strongly irregular rainfall concentrations. The Mann–Kendall analysis of the PCI values reveals that 8 of the 13 stations (62%) experienced downward trends. This implies that rainfall is sliding toward a moderate to uniform distribution. The trends, and consequently the variability in the annual and seasonal rainfall, reveal that, with the exception of Yola and Jos stations, where the trends were downward, the overall rainfall was increasing significantly in some areas and insignificantly in others. The magnitude of the significant upward trends in the annual rainfall was found to be 3.59 mm yr−1 at Yelwa station, 9.84 mm yr−1 at Bauchi station, 17.13 mm yr−1 at Kano station, 3.98 mm yr−1 at Sokoto station, and 3.11 mm yr−1 at Katsina station. It is understood that the changes in rainfall distribution and trends have positive effects on water availability for crops, and this should facilitate enhanced productivity in rain-fed farming.

中文翻译：

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尼日利亚萨凡纳地区降雨分布、时间趋势和变化率分析

摘要 气候变化的影响通常表现为降雨及其属性。因此，本研究分析了尼日利亚大草原地区的降雨浓度、时间趋势和变化率。从明纳联邦科技大学环境管理计划的档案中获取了 13 个天气站的 1970-2016 年年度、季节性和月度时间尺度的降雨数据。数据分析采用降水浓度指数(PCI)、Mann-Kendall趋势检验、Theil-Sen斜率估计(β)和相对百分比变化方法。研究结果表明，按年度计算的 PCI 分为三类 11-15、16-20 和 PCI > 20。计算的 PCI 中出现了两种不同的模式，表明几内亚大草原带（Bida、Yola、Minna、Jos、Bauchi 和 Kaduna）具有中等、不规则和极不规则的降雨浓度，而位于苏丹-萨赫勒大草原地带（卡诺、古索、迈杜古里、耶尔瓦、恩古鲁、索科托和卡齐纳）的站点具有不规则和极不规则的降雨量降雨浓度。曼肯德尔对 PCI 值的分析表明，13 个站点中有 8 个（62%）经历了下降趋势。这意味着降雨量正朝着中等至均匀分布的方向滑动。这些趋势以及年和季节性降雨量的变化表明，除了 Yola 和 Jos 站的趋势下降外，总降雨量在某些地区显着增加，而在其他地区则不显着。在 Yelwa 站发现年降雨量显着上升趋势的幅度为 3.59 mm yr-1，Bauchi 站为 9.84 mm yr-1，Kano 站为 17.13 mm yr-1，Sokoto 站为 3.98 mm yr-1，Katsina 站为 3.11 mm yr-1。据了解，降雨分布和趋势的变化对作物的可用水量有积极影响，这将有助于提高雨养农业的生产力。