Isah Abdullahi Tanko1,3, Tayo Iyanda Yahaya1, Aishetu Abdulkadir1, Joel Aghaegbunam Ezenwora2, Wakil Malah Bukar4, Ishiaku Ibrahim1, Abdulrazak Tijjani Kura1, 5
1Department of Geography, Federal University of Technology, P.M.B. 65, Minna, Niger State, Nigeria.
2Department of Physics, Federal University of Technology, P.M.B. 65, Minna, Niger State, Nigeria.
3Nigerian Meteorological Agency (NiMet), National Weather Forecasting and Climate Research Centre, Abuja, Nigeria.
4Department of Geography, Kashim Ibrahim University, Maiduguri, Borno State, Nigeria.
5Department of Geography, Kano University of Science and Technology, Wudil, Nigeria.
*Corresponding author’s Email: tankoiaphd179@st.futminna.edu.ng, doi.org/10.55639/607.020100125
ABSTRACT
Understanding rainfall variability is essential for climate adaptation, agricultural planning, and water resource management in the Sudano-Sahelian region of West Africa. This study examined rainfall variability and hydroclimatic behaviour across northwestern Nigeria using NASA-POWER rainfall data (1983–2024). Rainfall trends, persistence, oscillatory behaviour, and hydroclimatic anomalies were analysed using Mann-Kendall trend testing, Sen’s slope estimation, autocorrelation analysis, wavelet analysis, and the Standardised Precipitation Index (SPI). The results revealed substantial spatial and temporal variability in rainfall across the region. Statistically significant increasing rainfall trends were observed in Katsina, Kebbi, and Sokoto States, while Zamfara exhibited a significant decreasing trend (p < 0.05). However, no significant long-term trend was detected for northwestern Nigeria as a whole, indicating that strong interannual fluctuations dominate regional rainfall variability. Autocorrelation analysis revealed strong seasonal persistence but weak annual rainfall memory, while wavelet analysis identified significant oscillatory behaviour across multiple temporal scales. The SPI analysis further showed alternating wet and dry phases, highlighting the recurrent occurrence of hydroclimatic extremes and rainfall anomalies. Although wetter conditions appeared more frequently in recent decades, the weak SPI trend suggests that caution is required when inferring long-term climatic transitions. The study concludes that rainfall variability in northwestern Nigeria is characterised by spatial heterogeneity, weak long-term persistence, evolving oscillatory behaviour, and recurring hydroclimatic extremes. These findings provide valuable insights for climate adaptation planning, drought preparedness, and sustainable water resource management within the climate-sensitive Sudano-Sahelian region of West Africa.
KEYWORDS
Hydroclimatic extremes, Mann-Kendall test, Rainfall variability, Wavelet analysis.