Trends in the Spatial Extent of Precipitation Over West Africa in the Twentieth Century

Rainfall within the West African region is vital for domestic, industrial, agricultural, and socio-economic reasons. Excess or absence of sufficient rainfall, therefore, poses a significant threat to the region. Several factors, including large-scale oscillations, contribute to rainfall intensities in West Africa. Over the years, much attention has been paid to the point process and rainfall dynamics, not the spatial extent of rainfall. This study uses Mann–Kendall trend analysis to study the spatial extent of widespread precipitation over West Africa. Widespread rainfall is concerned with the percentage of an area within a region covered by a rainfall event. An increase or decrease in widespread rainfall over a long period indicates the role of climate change within the region. This information can be used to mitigate and adapt to the changing climate. In this study, rainfall for the twentieth century was obtained from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) over the West African region (0–15° N, 18° W–20° E) at a resolution of 0.5 × 0.5° grid. The spatial extent of daily precipitation was considered at thresholds of 1, 5, and 10 mm over ten decades. Results obtained showed that the spatial extent of precipitation has vastly been decreasing at all thresholds (1901–1910, 1921–1930, 1931–1940, 1941–1950, 1951–1960, 1961–1970) with increasing trends observed in fewer decades (1911–1920, 1970–1980, 1981–1990, 1991–2000). During the period, widespread precipitation showed decreasing trends of − 0.007, − 0.003, and − 0.011 for 1 mm, 5 mm, and 10 mm thresholds, respectively.