REGIONAL VARIATIONS IN FLUCTUATIONS OF SEASONAL RAINFALL OVER NIGERIA

Previous work on rainfall variations over Nigeria has concentrated on country-wide averages, which approach has tended to mask the regional contrasts in the country's rainfall. In this paper, variations of rainy season rainfall over the Southern, Middle Belt, and Northern regions of Nigeria as well as the country as a whole are examined over a 72-year secular period (1916-1987). The extent and nature of non-random changes, such as fluctuations, trend and persistence, are investigated. The trend analysis showed a tendency towards decreasing seasonal rainfall totals in all the regions, though only those for the Northern region and the country as a whole were significant. No significant persistence was however evident in any of the regions. Power spectrum analysis revealed the occurrence of significant oscillations with time periods of 2.53 to 2.67 and 3.69 to 4.36 years only in the Middle Belt, and 8.00 to 9.60 years in all the regions. The climatological identity of the Middle Belt and the implications of its rainfall oscillations for the large scale agricultural projects planned for the region are pointed out.