RELATIONSHIP OF EL NINO/SOUTHERN OSCILLATION TO RAINFALL PATTERNS IN NIGERIA

This paper examines the relationship between El Nino/Southern Oscillation (ENSO) and rainfall patterns in Nigeria. Annual rainfall totals, growing season rainfall totals and annual raindays of 27 Nigerian meteorological stations with varying lengths of records from 1903 to 2012 were collected from the Nigerian Meteorological Agency (NIMET). Monthly Sea Surface Temperatures (SSTs) anomalies data over Atlantic and Pacific Oceans and Southern Oscillation Index (SOI) were obtained from Climatic Prediction Centre (CPC). Kendall tau statistics and StepWise Multiple Regression model were used for data analyses. Results from this study showed that annual rainfall totals, growing season rainfall and annual raindays series exhibited a significant downward trend at most of the stations over the period of the study. It was observed that annual rainfall pattern changed from a positive pattern within 1931- 1960 period to a negative pattern within 1961-1990 period and then, to a positive pattern within 1991-2012 period. It was concluded that he alternating wet and dry patterns in inter-annual rainfall fluctuations and by extension, the droughts and floods over Nigeria within the study period, were caused by sea surface temperature anomalies over the Atlantic and Pacific Oceans. The paper therefore concludes that SSTs should be integrated in the seasonal rainfall prediction models in Nigeria for an improved forecast.