A centurial analysis of rainfall variability in Nigeria

Abstract

This paper examines rainfall variability in Nigeria using monthly rainfall data from 1901 to 2012. This is necessary for planning and management of agriculture and water resource systems. Data for the study were retrieved from the portal archives of World Bank Climate Change Knowledge. Descriptive statistics, trend analysis, and seasonality index were employed in the study. Fluctuations across the months and years were respectively examined through MAKESENS® statistics and Seasonality Index. The result revealed minimum and maximum amounts of rainfall in January and August respectively. The Z and Q statistics indicate an upward trend and positive slope respectively but the null hypothesis of no trend is accepted only in November, December and January due to very low amount of rainfall. The highest maximum and minimum amount of rainfall occurred in July and August while the lowest maximum and minimum both took place in January but the years in which these sets of maximums and minimums happened each followed a zigzag pattern which connotes fluctuations in the amount of rainfall. The maximum, minimum and average seasonality indexes are 0.924, 0.706 and 0.779 respectively, which indicate seasonal and markedly seasonal with a long dry season. There is the need to harvest, store and treat excess water during the wet months for use in dry months. The study recommends that the ministry of water resources should adopt best practices to provide water for Nigerians during the long dry months.

On the Generalized Pareto Probability Density Function of the Mean Annual Rainfall of Katsina State

“…The high variability of the mean annual rainfall established in our present study may be attached to the aggregate monthly variability of the rainfall. This conforms with [21] which established disparity in the variability of rainfall of different decades. The differences in the GPD of the different sites as bestowed by the shape parameter (k) established in our present study confirm with properties of Generalized Extreme value [10].…”

“…The rainfall trends were similar to that of locations in the Sahara region [20] but differ from both the declining trends obtained for Northern Nigeria [2] and the zig-zag trends (a very wide range of flunctuation) obtained for the entire Nigeria [21]. The disparity may however be due to the scope of the research in each of the study.…”

“…The disparity may however be due to the scope of the research in each of the study. The latter [21] covered the whole Country (Nigeria) while the present study covers just a state of the Federation. Similarly, the rainfall pattern of Abuja, a site within the same region as this study site (Katsina) unlike the present study gave a declining trend over the 31 years [22].…”

A Note on Rainfall Variability and Trends in Nigeria: Implications for Agricultural Production

“…Many studies have investigated rainfall trends and variability over the years in Nigeria, with most studies using tables and graphical plots to shed light on the dynamics of rainfall trends and variability over time (Adenodi 2018; Akinsanota & Ogunjobi 2014; Animashaun et al, 2020; Nnaji et al, 2016). In addition to this, some studies used time series analysis to investigate long fluctuation patterns in rainfall over an extended period (Ogbuene, 2010), while others used a non-parametric test to study rainfall trends in Nigeria (Obot et al, 2011).…”