Decadal Variability of Atlantic Warm Pool Dynamics and Its Teleconnection with Nigerian Rainfall

The Atlantic Warm Pool, defined as the region of the Atlantic Ocean with sea surface temperatures exceeding 28 degrees Celsius, exerts a significant but theoretically underspecified influence on West African monsoon dynamics, with implications for the interannual and decadal variability of rainfall over Nigeria's northern states and the Lake Chad Basin. This dissertation investigates the mechanisms linking Atlantic Warm Pool extent and intensity variability to Nigerian rainfall at seasonal to decadal timescales using a combination of observational analysis, ocean-atmosphere reanalysis products, and targeted climate model experiments. Extended observational analysis spanning 1980 to 2024 employs HadSST4 sea surface temperature data, ERA5 atmospheric reanalysis, and Global Precipitation Climatology Project rainfall datasets to characterise the co-variability between Atlantic Warm Pool metrics and Nigerian regional rainfall anomalies. Partial correlation and wavelet coherence analyses separate the Atlantic Warm Pool signal from confounding influences of the Indian Ocean Dipole and El Nino-Southern Oscillation. Model experiments using CESM2 with prescribed Atlantic sea surface temperature anomalies isolate the dynamic atmospheric response over West Africa. Multi-model ensemble analysis from CMIP6 models characterises projected changes in Atlantic Warm Pool extent under SSP2-4.5 and SSP5-8.5 scenarios to 2100 and assesses implications for future Nigerian rainfall distribution. The dissertation's theoretical contribution lies in proposing and testing a novel moisture flux convergence pathway through which a more extensive Atlantic Warm Pool enhances Guinea Coast rainfall while simultaneously suppressing Sahelian rainfall across the North West and North East geopolitical zones. Keywords: Atlantic Warm Pool, Nigerian rainfall teleconnection, decadal variability, West African monsoon, CMIP6