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 potential 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.
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