Trend Analysis in Rainfall Variability in Parts of North Central States, Nigeria: A Non Parametric Approach

Abstract

Rainfall variability and change, its impacts and the associated vulnerabilities is a growing concern across the globe. It is believed to be one of the greatest impediments for achieving food security and sustainable crop production globally. The study utilized 30 years Climate Prediction Center, Merged Analysis of Precipitation (CMAP) data. Non-parametric test, Mann-Kendall test and Theil-Sen slope estimator (β) to investigate the spatio-temporal trend and rate of change in rainfall over the study area. The monthly rainfall charactristics shows signficant downward trend at the onset period in May at 0.05 and 0.1 alpha values in Lokoja and Abuja while at the cessation period in October, signficant upward trend at 0.5 alpha value was detected in Lafia stations. The rate of the significant upward trend in the seasonal rainfall were 4.56 mm yr-1 at Lafia in the month of September, 3.72 mm yr-1 at Lokoja in the month of October and 6.06 mm yr-1 at Lafia in the month of October, respectively. The study revealed that the lowest coefficient of variation in seasonal rainfall occurred in Ilorin at 20.36% while the highest occurred in Lafia station at 37.79%. The result of annual Coefficient of variation also shows that Ilorin station has the lowest variation at 17.82% and the highest was found in Lafia at 37.7%. It is established that changes in rainfall pattern have impact on crop production. The study therefore recommend mainstreaming of farming calendar into the changing climate regime to ensure improved crop yield.