X-Raying Rainfall Pattern In Gombe State Over The Last Three Decades

In this work, monthly and daily rainfall records of 1977-2008 for Gombe station and that of Tumu which covers the period of 19651997 as well as that of the other nine stations across the state were analyzed to describe changes in rainfall seasons, duration, number of rain days as well as the amounts of rainfall received per a given rainy season. It was observed from the data analyzed that there was delay in the starts and ends of rainy seasonin the northern parts of the study area of about 14 to 21 days. In the same vein, the numbers of rainy days as well as the amount of rainfall received in the two parts of the study area vary significantly when correlated. For example, rains lasted for about 36-59 days at Billiri station (lat 09 o 51 ́50 ̋) with 684.56mm mean annual rainfall in the southern Gombe, while Dukku(10 o 36 ́15 ̋) in the northern part showed 17-55 rainy days with 650.27mean annual within the same period. The average duration of the rainy season in the southern parts of the state (which is influenced by highland among other things) had 6-8 months, while that of the semi-Sahel area by the north was found to be only between 4-6 months. This also indicates that the duration of rainy season steadily decreases with increase in latitude. When the total rainfall was correlated with the number of rainfall days of all the stations using Matrix Laboratory (MATLAB) environment; the results of the correlation coefficient indicated that there was correlation between the rainfall amounts and the number of rainfall days across all the stations in the study area. The correlation coefficients even though with varying degrees of freedom (Table 9 i.e. n-1) are as follows: Gombe 0.1506; Billiri 0.2559; Kumo 0.7053; Talasse 0.0372; Kaltungo 0.6189; Dukku 0.5122; Bajoga 0.6929; Nafada 0.3549; Deba 0.5281 and Tumu 0.1293. The results of the Student t-test is such that the Student’s ttest of the five stations out of the ten did not show significant relationships at 1% and 5% levels of confidence. These stations are Billiri,Deba, Gombe, Nafada, Talasse and Tumu. On the other hand, the remaining stations i.e. Bajoga, Dukku, Kaltungo and Kumo did show relationships. Hence, the study confirms that rainfall amounts vary over space and time.