Decadal Rainfall Trends and Variability Across Nigeria

Abstract

This work examined the decadal trends and variability of rainfall data over Nigeria from 1979 to 2021 (42 years). Observational monthly rainfall data was obtained from the Nigerian Meteorological Agency (NiMET). The data underwent statistical analysis to illustrate its spread and variability using metrics such as mean, standard deviation, and coefficient of variation, linear regression was applied to reveal the trends or changes over time, the coefficient of correlation was employed to assess the statistical relationships of rainfall across the distinct climate regions of Guinea, Savanna, and Sahel, respectively.  There were varying levels of annual and seasonal rainfall across the regions, with Port Harcourt receiving the highest annual and seasonal rainfall in the Guinea region. Sokoto and Maiduguri exhibit the highest annual rainfall in the Sahel region. The decadal analysis highlights the fluctuations in rainfall anomalies, as some decades showed surplus rainfall while others displayed negative deviations, indicating the changing nature of regional rainfall patterns.