SEASONAL VARIATIONS IN THE EARLY AND MID-YEAR RAINSTORM CHARACTERISTICS IN IBADAN, NIGERIA

Abstract

A rainstorm is a relatively short period of uninterrupted and intense rainfall. However, spatial and temporal variations are known to occur in rainstorms through the year. These temporal variations are largely due to seasonal changes in weather characteristics. Previous studies have largely characterised variations in rainstorm based on limited data from rainfall stations that are not evenly distributed over the city of Ibadan, hence their inability to analyse the seasonal variations of rainstorm characteristics at the metropolitan level. This study analysed the seasonal variations in rainstorms duration, rainfall amount, intensity, speed and areal coverage of rainstorms in the early and mid-year rainstorm events in Ibadan, Nigeria. A 3x3 km grid was superimposed on the map of Ibadan metropolis and one raingauge was installed in each of the 50 resultant grids. Rainstorms data were recorded daily from the 50 rainfall stations during the early and mid-year rainstorm events of 2013 and 2014. Descriptive statistics and Student's t-test were used to analyse the data, at p≤0.05. Out of the 48 rainstorms studied, 66.7% showed data for early rainstorms. There was significant difference in the mean duration of rainstorm between the early and mid-year rainy seasons (t=3.68). Results from this analysis could potentially be used to provide a baseline for future investigations of dynamics of rainstorms in urban areas.