The Impact of Climate Variability and Trends on Drought Over Benin: A Statistical and Conceptual Approach

Abstract

This study assessed drought trends and variability in Benin and their relationship with climate modes such as El Niño–Southern Oscillation (ENSO), the Atlantic Interhemispheric Sea Surface Temperature Gradient (AISSTG), and the Pacific Decadal Oscillation (PDO). Drought intensity, duration and frequency were analysed using the Standardised Precipitation Index (SPI) from monthly precipitation data at six weather stations (Bohicon, Cotonou, Kandi, Natitingou, Parakou and Savè) for 1970–2015. Nonparametric tests showed that all stations had random, independent, homogeneous and stationary 12-month SPI series, except for Kandi and Parakou, which exhibited autocorrelation and a significant positive trend (p > 0.05). No significant trends were observed at other stations. Significant correlations were found between the 12-month SPI and both the Multivariate ENSO Index (MEI, r = −0.35) and the PDO index (r = −0.30). Principal component analysis (PCA) revealed wet years in Benin during negative MEI and PDO phases. Droughts of higher intensity and duration were more frequent (54%) during El Niño/Neutral and warm PDO phases, whereas wet years (56%) occurred during La Niña and cool PDO phases. Extreme drought events (SPI < −2) were more common (89%) from 1970 to 1995, coinciding with high positive MEI and PDO values, whereas intense wet years (SPI > 1.5) occurred more often (64%) from 1996 to 2010. Harmonic and spectral analyses identified dominant dry/wet frequencies of 5–7.5 and 2–4.5 years. Stations nearest the coast (Cotonou, Bohicon) and in northern Benin (Kandi) experienced more frequent extreme events (14–16 events). These findings highlight the significant influence of climate variability on interannual and decadal precipitation patterns in Benin.