RAINFALL VARIABILITY AND DROUGHT INFERENCE IN SUDANO-SAHELIAN REGION OF NIGERIA

Abstract

Rainfall variability in Sudano-Sahelian regions of Nigeria (SSRN) over the 20th century and its poten-        tial links to the Sahelian drought have been examined using daily rainfall series from seven synoptic        stations in SSRN. Using the 30 year climate interval (i.e., 1940-1970 and 1970-2000), the percentage        changes in mean monthly rainfall depth and number of rain days, ranges between 4 and 33% for the        core season and between 3 and 70% in the marginal periods. The standardized rainfall index (SRI)        and normalized rain day index (NRI), two statistical descriptors, are defined and used in this study to        highlight the variability in rainfall and infer drought occurrence in SSRN. Both indices reveal that the        temporal variability in the amount and distribution of rainfall and number of rain days observed within        the region have to a large extent contributed to the 1973 and 1984 drought occurrences in the region.        Similarly, the relatively low NRI values observed within the region for the recent years may also be an        indication that the drought conditions since the early 1970s might be reoccurring.