Rainfall has been widely studied in terms of distribution over space, time and trends including onset and cessation. In any regional study of agricultural production rainfall is therefore of fundamental importance. This is very useful for decision making in issues of food security and other sectors affected by rainfall. This study seeks to assess rainfall variability in some selected stations in north eastern, Nigeria. The data used for this study are monthly rainfall in terms of amount and number of rain days. The data were collected from six (6) synoptic weather stations of the Nigerian Meteorological Agency (NIMET) for a period of thirty years (1983-2012). The selected stations include – Bauchi, Gombe, Maiduguri, Potiskum, Nguru, and Yola. Rainfall variability was assessed using mean and annual rainfall, rainfall anomaly index, coefficients of variance, and regional index techniques. Results showed Nguru recorded the least in both mean annual rainfall and rain days with the values of 402.40mm and 10days over the period, while the highest mean annual rainfall and rain days were recorded in Yola. The maximum amount of annual rainfall was observed in Bauchi with a value of 1621.10mm and the maximum number of rain days was recorded in Yola with 182 days. Variability was found to be highest in Maiduguri with coefficient of variability of 28% and the least was Gombe with 15%. In rain day, the station with highest variability was Yola with 29% and Gombe with the least variability at 14%. The year 2007 had the highest mean of rainfall and coefficient of variability on the number of rain days with the value of 79 days and 70% respectively. While, the lowest mean of rainfall and coefficient of variability on the number of rain days was 1983 and 2008 respectively. There was a genuine climatic trend within this period. All stations under study are characterized by uneven distribution of annual rainfall. The regional index is negative for about 40% of the years as opposed to 60% for positive values. These results also created a window for further studies to assess the influence of rainfall on crops and the periods of occurrence of drought in the study areas.
Keywords: Rainfall, Variability, Rain days, Agriculture