Spatio-temporal Analysis of Dry and Wet Spells in the Middle Belt of Nigeria

Abstract

The spatial patterns and trends of various categories of dry and wet spells were analysed from 1981 to 2010 in the Middle Belt of Nigeria. Daily rainfall (mm) data were obtained from eight synoptic weather stations spread across the region. The spatial variation and temporal trend of spells were analysed using the coefficient of variation (CV) and Pearson’s correlation coefficient (r). The result reveals that spatially, dry spells varied from 12.8 to 110.1%, while wet spells varied from 11.7 to 192.5%. The longest dry spell length by station ranged from 14 days (Jos) to 37 days (Yola), while the longest wet spell ranged from 7 days (Bida, Ibi and Makurdi) to 11 days (Ilorin and Jos). Both dry and wet spells exhibited positive and negative trends. Significant trends of dry spells include negative trends of categories 2–4 days (Ibi), 8–10 days (Yola), 11 days+ (Ilorin and Yola); and positive trends of categories 2–4 days (Lokoja) and 8–10 days (Ilorin). For wet spells, only positive trends were significant. The study concludes that the south western (northern) part of the region recorded the highest (least) annual frequency of dry spells and least (highest) annual frequency of wet spells, respectively.