Spatial Variation and Pattern of Daily Rainfall Intensity in the Middle Belt Region of Nigeria
Johnson O. Mage *
Department of Geography, Benue State University, P.M.B. 102119, Makurdi, Post Code 970001, Nigeria.
Bernard T. Tyubee
Department of Geography, Benue State University, P.M.B. 102119, Makurdi, Post Code 970001, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
The study analyzed the spatial variability of daily rainfall intensity in the Middle Belt region (MBR) of Nigeria for 46-year period (1961-2006). Daily rainfall (≥0.3mm) data were collected from eight synoptic weather stations in the study area. Daily rainfall intensity were classified into six categories using percentiles (P) namely; extremely light (≤ P10), light (P11 - P20), moderately light (P21 – P50), moderately heavy (P51 – P80), heavy (P81 – P90) and extremely heavy (> P90). To compute the percentile threshold values of the intensity categories, the population of rain days was first extracted and then ranked. The threshold values of the percentiles were extracted for each of the six categories among the eight stations and the annual number of daily rainfall for each station were then determined. The result showed a zonal pattern of increase in annual number of days for extremely heavy and heavy events from eastern to western parts of the MBR. There are enclaves of high annual rain days for the light and moderate categories in Jos plateau. The study concludes that the spatial variation will have tremendous impact on water resources and crop production as well as hazards of erosion and flooding.
Keywords: Orographic effect, moisture, enclaves, percentile, extreme rainfall.