Study and characterization of rainfall intensities in Akure, Southwestern Nigeria

Measurement and characterization of rainfall in a tropical location such as Akure, Southwestern Nigeria, (7.3°N; 5.3°E) is important to various fields of applications. Amongst these are water resource management, agriculture, climate studies, environmental sciences and telecommunications. In this paper, we present the statistical analysis of rainfall rates, measured with high temporal resolution of one-minute integration time, during the occurrence of some rain events in Akure. Rainfall intensities of one-minute integration time were measured using a Davis Vantage Vue Integrated Sensors Suite (ISS) weather station for the months of June 2013 to February 2014. The study investigates the pattern of rainfall distribution, temporal and cumulative distribution of rain rates, and their contribution to the total rainfall. The rainfall pattern in Akure may be categorized as mainly stratiform with less than 10% convective rains. High intensity convective rains were more prominent in the rain-deficient months, making it difficult to clearly demarcate between the conventional dry and rainy seasons in Nigeria. Comparison of measured rain rate with ITU-R indicates that the ITU-R model underestimates rainfall intensities at higher rain rates above 25mm/h, and above 99.5% of times, while it closely estimates intensities at lower rates below 20mm/h and for 99% of times.