This study investigated the impact of recent West African monsoon seasonal rainfall on the vegetation trend in Nigeria. Using Mann-Kendall test, the satellite estimates revealed increasing trends in the mean Normalized Difference Vegetation Index (NDVI) at 95 % in area of the location between 1981 and 2020 with statistical significance (atα≤0.5 levels of significance) in the south-western States. The 6-month Standardized Precipitation Index (SPI) from the Climate Research Unit (CRU) observational rainfall within the same period indicated increasing trends at 73 % of the area with statistical significance (at α≤0.5 levels of significance) in the northern States above the 9° N latitude. From the temporal correlations between the seasonal rainfall and vegetation trends, there was significant (at 95 % confidence level from the t-test) positive characteristic impact on 89 % of the area. The CORDEX-Africa historical experiment outputs (1981–2005) of the selected models and the ensemble mean revealed strong correlation values with high normalized RMSE when representing the seasonal rainfall simulation. The bias-corrected output (2006–2020) in the RCP 8.5 experiment showed notably enhanced representation quality of the models and the ensemble mean, with 87 % of the area demonstrating “reasonable performance” efficiency. The 6-month SPI projection from 2021 to 2050 indicated positive trends in 84 % of the area. Indeed, the relative percentage difference between projected and baseline trends compellingly suggests a decrease in seasonal rains by 2050, intensifying the demand on vegetation and introducing additional climate challenges.

中文翻译：

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尼日利亚最近西非季风季节的植被趋势以及对 CORDEX-Africa 的近期影响


本研究调查了近期西非季风季节性降雨对尼日利亚植被趋势的影响。使用 Mann-Kendall 检验，卫星估计显示，1981 年至 2020 年期间，该位置面积的平均归一化差值植被指数 （NDVI） 呈增加趋势，为 95%，在西南部各州具有统计学意义（atα≤0.5 显著性水平）。气候研究单位 （CRU） 同期观测降雨的 6 个月标准化降水指数 （SPI） 显示，在北纬 9° 以上北部各州，具有统计显著性（α≤0.5 显著性水平）的 73% 的面积呈增加趋势。从季节性降雨和植被趋势之间的时间相关性来看，对 89% 的地区有显著的（在 t 检验的 95% 置信水平下）积极特征影响。所选模式的 CORDEX-Africa 历史实验输出 （1981-2005） 和集成均值在表示季节性降雨模拟时显示与高归一化 RMSE 的强相关性值。RCP 8.5 实验中的偏差校正输出 （2006-2020） 显示模型的表示质量和集成均值显著提高，87% 的区域表现出“合理的性能”效率。从 2021 年到 2050 年的 6 个月 SPI 预测表明，该地区 84% 的地区呈积极趋势。事实上，预测趋势与基线趋势之间的相对百分比差异令人信服地表明，到 2050 年，季节性降雨将减少，从而加剧对植被的需求并带来额外的气候挑战。