RAINFALL TREND IN THE SUDANO-SAHELIAN ZONE OF NIGERIA

Abstract

The climate of sudano-sahelian belt is characterized by alternate wet and dry season in response to the changes in pressure patterns. This gives rise to two distinct prevailing air masses over the country at different times of the year. The rainy season in this region is associated with late onset and earlier cessation, the onset and cessation are characterized with destructive storm. It was also revealed from the findings that there is higher mean rainfall than the long-term mean in the earlier decade of 1958 – 1967, while the decades from the early 1970s to the mid-90s show declining rainfall total. An attempt is also made to use trend analysis to see the rainfall variations over four stations (Kebbi, Yobe, Sokoto and Katsina) in the zone. Rainfall data for 50 years in the zone were tested using 5-year and 10-year running mean. The whole period was divided into decades and the decadal means compared with long-term mean. Results indicate a decrease in annual rainfall in the zone from the mid 1970s up to the mid 1990s. Recent trends, however, show increase in annual rainfall from the mid 1990s. The importance of this for agricultural and water resources planning and development cannot be over emphasized.