Rainfall distribution and change detection across climatic zones in Nigeria

Nigerian agriculture is mainly rain-fed and basically dependent on the vagaries of weather especially rainfall. Nigeria today has about forty-four (44) weather observation stations which provide measurement of rainfall amount for different locations across the country. Hence, this study investigates change detection in rainfall pattern over each climatic zone of Nigeria. Data were collected for 90 years (1910–1999) period for all the weather observation stations in Nigeria, while a subdivision was made to three (3) non-overlapping climate period of 30 years i.e. 1910–1939, 1940–1969 and 1970–1999. Statistical methods were utilized to justify any change in the average monthly and annual rainfall trend using probability density function and non-parametric tests such as the Pettitt test, Wilcoxon signed-rank test and paired sample test. Results show common change points and transitions from dry to wet (upward shift) in all climatic zones. Statistical tests performed on the data show that rainfall variation over each climatic zone is significant (p<0.05) between pairs of climate periods. Suggestions were therefore made at the end of the study on the use of the contained information for socio-economic improvement and agricultural development of the zones.