Analytical Study of the Relationship Between Atlantic Sea Surface Temperature Anomalies and Rainfall Variability Over South West Nigeria

The climatic influence of Atlantic Ocean sea surface temperature (SST) variability on West African rainfall is a well-established but spatially heterogeneous relationship that demands local-scale empirical validation. This study analytically examines the statistical relationship between Atlantic SST anomalies and rainfall variability over Southwest Nigeria (Lagos, Ogun, Oyo, Osun, Ondo, and Ekiti states) using 40 years of monthly rainfall records from 12 NiMet stations and gridded SST data from NOAA ERSST v5. Partial correlation analysis, wavelet coherence, and composite anomaly mapping were applied to disentangle the relative influences of tropical Atlantic, equatorial Atlantic, and Mediterranean SST patterns. Results reveal a robust positive teleconnection between warm Atlantic Nino events and above-normal first rainy season rainfall (April to June) over coastal Southwest states, with correlation coefficients of 0.61 to 0.72. The relationship weakens significantly during the second rainy season (September to October) when remote SST forcing is modulated by local continental convective dynamics. A novel finding is a significant negative correlation between Mediterranean SST and second-season rainfall that has strengthened since 2010, suggesting an emerging teleconnection not previously documented for Southwest Nigeria. Empirical seasonal prediction equations derived from significant SST predictors demonstrate skill scores superior to climatological persistence for first-season rainfall, with potential for operational incorporation into NiMet's Southwest seasonal outlook. Keywords: sea surface temperature, rainfall variability, Southwest Nigeria, teleconnection, seasonal prediction.