22 years characterized trends of rainfall in Abeokuta, Nigeria

Abstract

Many processes are dictated by rainfall so the knowledge of the trends of rainfall in the respective localities is very important amidst the concern of the effect of anthropogenic activities. To this end the rainfall trends in terms of cumulative total amount and total number of rain days in Abeokuta (7°15'N, 3°35'E) Nigeria for 22 years (1981-2002) are investigated using the Mann-Kendall non parametric test. The results of the Mann-Kendall Z test for both cumulative total rainfall amount and rainy days are 0.90 and 1.47, respectively. The test values for dry season and raining season partitions of the same period for both parameters are 0.56, 0.45 and 0.39, 0.50. All the results even with monthly evaluations at 90% confidence level indicate no significant trend and activities like farming can be carried out in accordance with established rainfall pattern without fear of change, though continues monitoring is advised to detect any possible U-turn. While the yearly cumulative rainfall seemingly does not depend on solar intensity, its seasonal variability is in tune with sun earth distance. © 2011 Medwell Journals.